Virtual Reality Application in Evaluating the Soundscape in Urban Environment: A Systematic Review

Abstract

Urban soundscapes are complex due to the interaction of different sound sources and the influence of structures on sound propagation. Moreover, the dynamic nature of sounds over time and space adds to this complexity. Virtual reality (VR) has emerged as a powerful tool to simulate acoustic and visual environments, offering users an immersive sense of presence in controlled settings. This technology facilitates more accurate and predictive assessment of urban environments. It serves as a flexible tool for exploring, analyzing, and interpreting them under repeatable conditions. This study presents a systematic literature review focusing on research that integrates VR technology for the audiovisual reconstruction of urban environments. This topic remains relatively underrepresented in the existing literature. A total of 69 peer-reviewed studies were analyzed in this systematic review. The studies were classified according to research goals, selected urban environments, VR technologies used, technical equipment, and experimental setups. In this study, the relationship between the tools used in urban VR representations is examined, and experimental setups are discussed from both technical and perceptual perspectives. This paper highlights existing challenges and opportunities in using VR to assess soundscapes and offers practical insights for future applications of VR in urban environments.

1. Introduction

As global urbanization accelerates, managing urban soundscapes has become a critical challenge for public health and urban livability. Environmental noise, recognized as one of the most significant environmental risks to human health [1]. It continues to escalate alongside the growth of cities. With an estimated 70% of the global population expected to live in urban environments by 2050 [2], the effect of environmental noise on public health is expected to become even more critical. To address this challenge, research on urban soundscapes aims to enhance the quality and usability of urban life by evaluating audiovisual elements and user perceptions [3,4,5]. Conducting such studies in real-world settings presents numerous challenges. It includes the difficulty of controlling environmental variables, the cost and time required for large-scale urban projects, and the complexity of integrating user perception data. Thanks to recent advances, it is now possible to study urban soundscapes under controlled conditions with high ecological validity. These methods offer promising alternatives to traditional field experiments.

Urban acoustic research has shifted from simply reducing noise to focusing on user-centered perceptual experiences [6]. This shift calls for broader public involvement in urban design decisions, an opportunity that VR enables by allowing stakeholders to experience and evaluate urban soundscapes in controlled, immersive environments before costly real-world implementations.

Virtual environments have become a valuable tool for urban planners and architects by facilitating real-time visualization of urban data and encouraging user participation in the design process [7,8]. Applied across diverse urban contexts—from highways to green spaces—VR contributes to smarter, more sustainable, and environmentally conscious city planning [9]. Its controlled, immersive environments allow researchers to evaluate complex soundscapes and assess user perceptions such as comfort, annoyance, and pleasantness—critical factors for urban development projects [10,11].

VR-based studies on urban soundscapes that integrate auditory and visual elements are diverse. They address topics such as urban design, analysis of specific elements, restorative effects, and questions of ecological validity, as well as a wide range of technical approaches. In this review, we also include 360-degree audio-video recordings by analogy, as they are commonly used in experimental contexts for VR, even though they do not provide fully immersive virtual experiences. For instance, many recent studies have used 3D models to examine the impact of street scales on visual and auditory comfort [12,13]; evaluated urban regeneration alternatives by adding water and plants [14]; analyzed the visual and auditory effects of interior courtyards and facades [15], and employed VR to increase stakeholder and public engagement in planning [16,17]. Urban areas consist of multiple elements, and understanding the relationships among them is essential—especially within VR. Several studies have shown that green areas and blue elements have a positive effect on acoustic perception [18,19]. Water features have both visual and auditory positive effects on people’s perception [20]. A positive correlation has been observed between greenery satisfaction, environmental cleanliness, architectural esthetics, and soundscape evaluation [21]. These examples underline the importance of understanding the psychological, behavioral, and physiological processes underlying human–environment interaction in the development of VR applications.

A significant amount of research on VR in urban environments examines the restorative effect and stress recovery. Findings consistently show that incorporating both natural visual and auditory elements enhances the restorative impact of VR experiences [22]. In particular, green areas have demonstrated a stronger stress-reducing effect compared to other urban environments, supporting emotional recovery and relaxation. Findings highlight the combined impact of visual and auditory stimuli in VR, also reducing stress, and waterfront areas showing particularly strong restorative effects [20,23,24]. These findings highlight the central role of audiovisual interaction in shaping user perception, while studies on ecological validity have further emphasized the need to test the consistency of responses between real and virtual contexts [25]. In addition, individual factors such as personality traits, cultural background, age, place attachment, and familiarity also play a key role in reducing stress [26,27,28].

VR research in urban environments varies in its research objectives, selected environments, and the methodologies employed for recording and representation. Furthermore, considering the experimental setup, laboratory conditions, and questionnaires employed in the study, it can be seen that these investigations are quite diverse and difficult to understand. Despite the growing number of VR studies conducted in urban environments, there is a gap in the systematic review of existing publications on the evaluation of urban acoustics that incorporate audiovisual elements. Although several literature reviews have examined the usage of VR in urban environments [29], audio in VR [30,31,32], ecological validity and immersive virtual reality (IVR) [33], audiovisual interaction [4], relatively few have specifically addressed the intersection of audiovisual elements of VR and urban soundscape research. However, these studies do not analyze user perception, the impact of the visual, and the applications in different urban areas [30,31,32]. Moreover, the study of IVR and ecological validity in urban environments [33] is limited to these objectives, and comprehensive studies that examine audiovisual interaction in urban environments do not include VR [4]. This fragmented overview limits the ability to draw comprehensive conclusions about the state of research in this area. Therefore, a targeted systematic review is essential to bridge this gap. It should analyze studies that explicitly integrate VR and audiovisual elements for evaluating urban soundscapes, thereby providing a more cohesive picture of current practices and research agendas. This review intends to systematically assess existing VR-based urban soundscape studies. It also identifies key challenges and gaps and proposes actionable recommendations for future research directions.

Therefore, this systematic review aims to analyze how VR is currently used in the study of urban soundscapes, focusing on the research goals, methodologies, technologies, and contextual settings employed across studies. It seeks to synthesize fragmented findings from interdisciplinary research to provide a comprehensive understanding of how audiovisual elements in VR influence user perception in urban environments.

Specifically, this review focuses on (1) classifying existing VR-based urban soundscape studies according to their goals, environments, and methodological framework; (2) identifying common experimental equipment and challenges, and (3) suggesting future research directions to improve perceptual assessment and interdisciplinary applicability.

Particularly, this review is to provide researchers with assistance in developing more comprehensive strategies for audiovisual interventions. These strategies will be based on a more in-depth understanding of user perception, experimental setup, and the ever-changing technical background. It makes a contribution to the improvement of user-centered and environmentally responsible design methods. This assessment may offer a deeper understanding of the VR studies in urban areas and provide significant data for future research.

2. Materials and Methods

2.1. Search Strategy and Eligibility Criteria

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standards for systematic reviews are followed in the execution and reporting of this investigation [34]. The aim of the review was to examine how VR is utilized in soundscape research within urban environments, particularly focusing on studies that integrate both visual and auditory modalities.

Relevant papers were selected from Scopus, Web of Science, Google Scholar, Taylor and Francis, and Wiley online library. The search query consisted of the following keywords: “virtual reality” + “soundscape”. A total of n = 1297 candidate papers were identified across various searching databases by 31 December 2024, utilizing the previously mentioned keywords.

After removing duplicates, conference proceedings, book chapters, and previously published review articles, the remaining records were screened based on title and abstract. The inclusion criteria required studies to

• Focus on soundscapes as a central research theme;
• Utilize VR that includes both auditory and visual elements;
• It can be conducted in outdoor or urban environments.

Accordingly, studies using VR solely for either auditory or visual purposes, as well as those conducted in indoor settings and purely theoretical or conceptual papers, were excluded. The full texts of the remaining papers were assessed for eligibility by the author. A total of 69 unique papers met all criteria and were included in the final review.

During data extraction, key study characteristics such as research goals, field selections, type of VR setup (e.g., HMD, CAVE), type of audio implementation (e.g., binaural, ambisonic), participant sample details, and main findings were systematically recorded. Due to the considerable methodological heterogeneity among the included studies—such as variation in study design, data collection tools, and analytical approaches—a formal risk of bias assessment was not conducted. In addition, no specific assessment of publication bias (i.e., risk of bias due to missing results) was performed. Instead, the synthesis of findings was carried out narratively, without making comparative judgments about the methodological quality or reliability of individual studies. A summary of the study selection process is illustrated in the PRISMA flow diagram (see Figure 1).

2.2. Analysis of Search Results

The search results included relevant papers that were reviewed within the study’s scope, focusing on keywords such as “virtual reality”, “soundscape”. Figure 2 shows the number of studies conducted each year.

The first study on this topic was carried out in 2012. After 2017, studies have increased markedly. The selected literature for the study was categorized into two main groups: (1) research goals and field selections, and (2) laboratory experiments and the design of the experimental setup, including tools and audio–visual representations, as well as visual and auditory representations. This distinction was made to clarify both the research focus and the technical aspects of the studies. Figure 3 shows the classification of the studies.

In the first group, research goals to be examined the four thematic categories urban design and planning, analysis of urban elements, restorative effects, and ecological validity. These categories were identified through an iterative coding process applied to the objectives of the 69 reviewed studies. While additional themes might have emerged, these four were the most consistently represented across the literature, capturing both methodological and conceptual dimensions of VR soundscape research. First group were specifically focuses on the research goals rather than field selection. The second group focused on detailed technical issues related to the gathering of audiovisual data, its presentation methods, VR laboratories, and questionnaire- based evolution.

3. Results

3.1. Research Goals and Field Selections

VR studies conducted in urban areas are generally based on their objectives and field selection, with a focus on regenerating visual and auditory data. The selection of the field is also influenced by the goals of the studies; as urban areas designate a broad spectrum. Urban design and planning, analysis of urban elements, which is mainly focused on acoustics and visual elements, restorative effect, and ecological validity are the four key topics that emerge when the studies are categorized based on their primary objectives.

Table 1. Summary of studies on based on their research goals and field selections (n = 69).

Authors (Published Year)	Research Goals				Field Selections
	Urban Design and Planing	Analysis of the Urban Elements	Restorative Effect	Ecological Validity	Green Areas	Roadside and Transportation Corridors	Other
Engel and Döllner [17]	x					x	x
Maffei et al. [35]	x					x
Ruotolo et al. [10]	x					x
Maffei et al. [36]		x					x
Annerstedt et al. [37]			x		x
Shai et al. [38]		x					x
Jiang et al. [39]	x					x
Maffei et al. [25]				x		x
Puyana-Romero et al. [40]	x					x	x
Echevarria Sanchez et al. [41]	x					x
Yu et al. [42]		x					x
Liu and Kang [12]	x					x
Jiang et al. [43]		x				x
Jiang et al. [11]	x					x
Lugten et al. [14]	x						x
Taghipour et al. [15]	x						x
Hedblom et al. [23]			x		x		x
Hedblom et al. [44]			x		x
Sun et al. [45]		x			x	x	x
Jeon and Jo [3]		x			x	x	x
Sacchelli and Favaro [46]			x		x
Hong et al. [47]		x					x
Jo and Jeon [48]		x			x	x	x
Lindquist et al. [49]		x			x		x
Jo and Jeon [50]		x			x
Kern and Ellermeier [51]		x			x
Meenar and Kitson [52]	x					x	x
Park et al. [22]			x		x
Senese et al. [26]			x		x
Andolina et al. [53]	x						x
Berger and Bill [54]	x						x
Meuwese et al. [55]			x		x	x
Jo and Jeon [56,57,58]		x			x	x	x
Li et al. [59]			x		x
Jo and Jeon [60]		x			x
Jeon et al. [18]			x		x	x	x
Masullo et al. [61]	x		x		x
Puyana-Romero et al. [20]		x					x
Ha and Kim [62]			x				x
Jaalama et al. [63]				x	x		x
Llorca-Bofí et al. [64]	x						x
Bazrafshan et al. [27]			x		x
Oberfeld et al. [65]		x				x
Puyana-Romero et al. [66]		x					x
Ünal et al. [67]				x	x	x
Wessels et al. [68]		x				x
Lu et al. [5]	x	x					x
Ojala et al. [69]			x		x
Ch et al. [70]			x		x
Hsieh et al. [71]			x		x
Dongas et al. [72]	x			x		x
Mioni and Pazzaglia [73]		x			x	x
Weibel et al. [74]			x		x
Gao et al. [75]		x					x
Jeon et al. [76]			x		x	x	x
Lyu et al. [21]		x					x
Long et al. [28]			x		x	x	x
Yanaky et al. [77]	x					x	x
Yilmaz et al. [13]	x					x
Zhou et al. [78]		x					x
Meng et al. [79]			x		x
Chen et al. [80]			x		x	x	x
Shawabkeh and Arar [81]	x				x
Młynarczyk and Wiciak [82]		x			x
Yang et al. [83]				x			x
Kawai et al. [84]			x		x		x
Kari et al. [85]			x		x

categorizes studies based on their research goals and field selections.

The studies show substantial variation in field selections. Although there have been comprehensive studies conducted in many areas, there is a noticeable emphasis on specific regions, such as green areas or roadsides. Therefore, the field selection took into account two primary categories: green areas and roadside and transportation corridors. The other group, referred to as other areas, comprises many categories, including public, residential, and historical areas. Figure 4 shows the relationship between field selections and research goals.

In total, 69 studies were reviewed within the scope of this research. Of these, 26 studies were categorized under more than one field selection (e.g., a study analyzing both green areas and transportation corridors). For this reason, the total number across categories exceeds the total number of reviewed studies. When examining the distribution among field selection categories, 35 studies primarily investigated green areas, 27 studies focused on roadsides and transportation corridors, and 34 studies addressed other areas. An assessment of field selections reveals that while urban planning research often targets roadside and transportation corridors, studies on restorative effects are primarily conducted in green spaces. Research on the analysis of urban elements, as well as research on ecological validity, is more equitable distribution. The next part of this study involved a review of the literature, organized according to the research goals.

3.1.1. Urban Design and Planning

Urban design is one of the main topics of virtual reality studies conducted in urban areas. Urban design projects are substantial and costly undertakings involving large-scale planning and development. Therefore, it is crucial that design decisions are made within a virtual environment and that possible decisions are experienced in advance. VR enables urban planners and stakeholders to fully engage with three-dimensional (3D) representations of planned urban developments, providing an authentic experience of their size, dimensions, and visual and acoustic appeal. It is therefore crucial to conduct research in which the acoustic and visual consequences are experienced in advance, and planning decisions are actively altered in 3D.

Significant studies have been conducted to change the design decisions by employing a 3D model. In this context, Liu et al. [12] analyzed the impact of street scales (the street width, building height, and street-width-to-building-height ratio) on visual, acoustic, and audio–visual comfort evaluation in urban areas. The research shows that subjective attitudes are directly correlated with street scales. The street width-to-height ratio is significantly positively correlated with audiovisual comfort. Echevarria Sanchez et al. [41] evaluated the total value of future regeneration alternatives for the design of urban public spaces using VR. They showed that the auditory environment had a statistically significant impact on the overall level of pleasantness. The study presents extensive data on the correlation between visual and auditory factors. Surprisingly, the study indicated that a lower visual barrier design, rather than increasing the height of the noise barrier, was more successful in enhancing the perception of pleasantness. Visual designs incorporating vegetation outperformed alternative options. Lugten et al. [14] conducted an experiment investigating the use of water and plant elements for masking airplane noise. They indicated a notable enhancement in the quality of the soundscape when both vegetation and moving water are present, particularly when the vegetation and water sounds are combined. Berger and Bill [54] conducted a study where they converted traffic noise data into a three-dimensional model. In their study, they used the basic VR interactions typical of current mobile VR headsets in a prototype application, and combined with data visualization and sonification techniques, they worked on commodity low-cost VR hardware that should manage complicated noise level calculations in a real-time environment. The study conducted by Maffei et al. [35] examined the impact of the visual characteristics of a display on the noise perception by nearby residents. The study examined the impact on the assessment of perceived loudness and noise annoyance in relation to noise barriers. Yilmaz et al. [13] examined the effect of sound on the perception of enclosed space in urban street canyons by varying height/width ratios (H/Ws). The participant’s responses to the stimuli were assessed based on the perceived sense of being enclosed, the perceived sense of spaciousness, the perceived sense of pleasantness, and the perceived width of the source. The experiment’s findings indicated that as the H/W ratio increased, there was a decrease in the perceived enclosure, perceived spaciousness, and felt pleasantness of visual stimuli. In their study, Shawabkeh and Arar [81] assessed the utilization and preferences of virtual reality in relation to individuals’ engagement with neighborhood parks. They employed an experimental methodology to examine the factors affecting park visitation, utilizing both conventional techniques to assess the degree to which virtual reality can alleviate these obstacles. The study revealed that perception significantly influenced responses among individuals of various age groups. VR was also found to help overcome the problems associated with traditional research methods. Taghipour et al. [15] investigated the visual and auditory effects of interior courtyards and facade features in a virtual environment.

With VR technology, planning becomes a process in which all stakeholders can participate. It facilitates real-time collaboration among architects, planners, and stakeholders within a virtual model, simplifying discussions on design features and allowing for immediate modifications. Specifically, immersive visualization enables the simulation of planning scenarios and the acquisition of a close-to-realistic impression by both expert and non-expert stakeholders [17]. Visualization with the help of VR during planning facilitates the public participation process and helps stakeholders understand alternatives [16]. It supports the concept of digital democracy [86].

Studies on urban design and planning specifically highlight the simultaneous presence of various urban actors. Engel and Döllner [17] constructed a 3D model of the city and gathered all participants to collectively discuss urban planning decisions. By utilizing a method known as E-Planning, individuals are able to enhance their comprehension and perception of the consequences of upcoming projects, therefore enabling them to offer more knowledgeable and insightful input. The study conducted by Meenar et al. [52] highlights the importance of participatory planning in this context. Participatory planning prioritizes the involvement of the public and the utilization of digital instruments. Web-based technologies are extensively utilized to facilitate and achieve this participatory planning.

The impact of new technologies and tools on participatory planning has also been the subject of research. It is important to investigate the active use of different technologies in the field of planning and to explore the limits of new tools. Andolina et al. [53] discussed several technologies, such as VR, augmented reality (AR), and haptic–audio interaction, in urban planning decisions. Accordingly, the experiment participants stated that using visual AR allowed them to gain a comprehensive understanding of all the decisions they made during the experiment. By accurately placing the landmarks, they evaluated the audio-tactile interface in the environment as more enjoyable, innovative, adaptable, and inspiring. Yanaky et al. [77] have developed a tool to design an immersive soundscape. They focused on the user-centered design methodology that was used to create and assess City Ditty, an innovative tool for designing soundscapes. It is worth noting that the application of a user-centered design methodology was employed to identify and create features that would be advantageous to urban users who lack expertise in sound.

Additionally, research is conducted to develop various assessment methodologies and integrate them with emerging technologies. Dongas et al. [72] proposed the virtual urban field studies (VUFS) system for use in urban studies. VUFS is a human–computer interaction approach that considers many participant perspectives and aims at reproducing the experience as authentically as feasible through audio and video. They emphasized that the comprehensive methodology in their study can be applied to the design and evaluation of many other urban design interactions and interfaces. Belaroussi et al. [87] compared actual street observations and VR visits to analyze user perceptions and evaluate the quality of urban areas. A high-resolution 3D model of a large-scale neighborhood was produced for this project, using Building Information Modeling (BIM) and Geographic Information System (GIS) data. The study aims to understand the fundamental factors that impact individuals’ perception and utilization of a street. Additionally, in their study, they made significant contributions to understanding the significance of using VR for forecasting the quality of future environments.

Overall, the reviewed studies demonstrate the transformative potential of VR technologies in urban design and soundscape planning. These approaches not only enhance perceptual realism but also facilitate and emphasize stakeholder engagement, participatory planning, and the integration of multisensory data into design processes. While there is methodological diversity across studies, the common emphasis on immersive, user-centered evaluation reveals a growing shift towards experiential and evidence-based urban interventions. This body of research underscores the importance of developing VR-based tools and frameworks to support more inclusive, effective, and perceptually informed urban design practices.

3.1.2. Analysis of Urban Elements

The development of VR in urban environments, encompassing both audio and video components, is a relatively recent development. A significant portion of the research in this title focuses on investigating the effects of various audiovisual components on individuals’ perceptions. Although this section is generally titled ‘Analysis of Urban Elements,’ it primarily focuses on reviewing studies related to the transformation of acoustic and visual components in urban areas.

Researching perception changes in individuals focused on visual and acoustic elements will provide valuable guidelines for future research. This, in turn, will enhance our understanding and application of VR technologies. Besides that, it is well known that our visual and auditory perceptions are affected by each other [4]. Significant psychoacoustic research has shown that visual context can systematically influence loudness evaluation [88]. There are several compelling examples that illustrate the interaction between auditory and visual elements. Jo and Jeon [3] investigated the impact of audiovisual stimulation in various urban environments on individuals’ perception and overall satisfaction. They showed that the auditory information had a 24% impact on total satisfaction, while visual information had a significantly higher impact of 76%. They proposed overall satisfaction models based on soundscape and landscape components. Through subjective evaluations in VR, this study examines how the suitability of the acoustic environment influences urban soundscape perception. Results revealed that the appropriateness of sound sources interacts with individuals’ perception of visual elements, and that “traffic” sounds and “bird sounds” are very critical factors influencing participants’ initial perceptions of urban soundscape quality.

Audiovisual elements influence each other; however, it is important to determine the boundaries of their mutual influence. Lu et al. [5] showed the effect of audiovisual interaction on soundscapes in VR in the context of urban residential areas. In their study, they grouped visual elements according to the indexes they identified, like the Green View Index (GVI), Road View Index (RVI), Building View Index (BVI), and Playground View Index (PgVI). They found that GVI can positively affect pleasantness in conditions with no traffic and light traffic, while GVI does not affect pleasantness in heavy traffic conditions. Lindquest et al. [49] investigated the impact of visual information on perception in 3D visualizations. Five environments (vacant lot, community garden, habitat, woodlot, playground) were tested under three distinct auditory situations (no sound, ambient sound, detailed sound). The results of their study showed that detailed audio increased biodiversity evaluations, while the type of display had no effect. Ambient and realistic sounds were found to increase preference and realism.

A large number of studies investigating the impact of auditory stimuli in esthetically pleasant environments have predominantly been carried out in urban parks. It has been shown that green areas (e.g., trees, grass, plants) and the blue elements (e.g., sea, lakes, rivers) have a positive effect on our acoustic perception in urban environments [89]. These findings are consistent with the Tranquility Rating Prediction Tool (TRAPT), which estimates perceived tranquility in outdoor environments by integrating objectively measurable acoustic metrics (e.g., LAeq), natural and contextual visual features (e.g., vegetation, water elements), and auditory factors (e.g., natural sounds, traffic noise) [90,91]. Jo and Jeon [50] discussed the relationship between human perception and soundscape in urban parks. Their findings showed that while sounds from other people reduced the perceived tranquility of the park, they simultaneously enhanced its dynamic and lively atmosphere. They showed that the presence or absence of individuals, rather than the nature of human activity, was the primary factor influencing park preferences. A general evaluation of urban parks that investigated the relationship between visual and auditory was discussed in another study. Jo and Jeon [60] discovered that individuals’ pleasantness level was positively influenced by the addition of natural elements and the reduction in traffic. Furthermore, they found that vegetation and birdsongs influenced environmentally pleasantness. The study investigated how human behavioral traits influence soundscape perception in urban parks, revealing that park users are more affected by the mere presence or absence of other individuals than by the specific nature of their activities [50]. Studies have shown that the water element has visual and auditory positive effects on people’s perception. Puyana-Romero et al. [20] investigated the effects of waterfront soundscapes on human perception in seafront areas. They compared two scenarios that included the addition of water sound and those without. The findings indicated that all situations involving water sounds were perceived as more pleasant than the original situation. Hong et al. [47] examined how spatial distances between target noise (traffic) and masking sound (water) influence perceived loudness (PLN) and overall soundscape quality (OSQ). Auditory stimuli included recorded traffic noise and water sounds, paired with a spherical panoramic video of a fountain as visual input. Results showed that the perceived loudness of traffic noise decreased at 135°, while the water sound’s enhancement of soundscape quality weakened at both 135° and 180°. Zhou et al. [78] examined the connection between auditory and visual elements in their study. They revealed a positive correlation between greenery satisfaction, environmental cleanliness, architectural esthetics, and soundscape evaluation. Lyu et al. [21] investigated audiovisual-thermal perception in VR. Their study is important as it incorporates thermal data into the multisensory analysis. Their findings stress the importance of studying psychological, behavioral, and physiological dimensions to decode human-environment interactions. The study participants for integrated environmental datasets (sound, visuals, temperature) to advance this understanding. Jiang et al. [39] examined the influence of odor on multisensory evaluations of road traffic environments. In their study, they assessed perceived loudness, noise annoyance, landscape quality, and overall pleasantness across numerous situations. The presence of odor did not exert a significant primary effect on any of the results.

The analysis of urban areas of different acoustic character or different situations in virtual environments and the investigation of user perception are also part of the studies. Sahai et al. [38] focused on the virtualization and auralization of aircraft noise. They clarified various strategies and methodologies. Yu et al. [42] focused specifically on wind parks. In their study, they used VR to examine how both sound and visual elements of wind parks affect people’s perceptions. Puyana-Romero et al. [66] used immersive audio–visual scenarios to evaluate helicopter noise impacts in Quito City Park, Ecuador. Their VR study found that removing helicopter noise created a more pleasant soundscape and improved visual scenery evaluations under identical conditions. Oberfeld et al. [65] conducted studies on road safety and traffic psychology using VR. Studies examining pedestrian behavior during road crossings utilize both visual and auditory data [65,68].

Several studies focus specifically on assessing the efficacy of the employed methods and measurement tools in VR. Jo and Jeon’s [57] study provides a representative example, systematically evaluating the efficacy of the soundscape methodology. In their research, they reexamined the data acquisition methods outlined in ISO 12913-2 [92]. It provides essential information for performing soundscape research in virtual reality. Sun et al. [45] explored a hierarchical classification method that distinguishes between background and foreground, disturbing and supportive, and finally calming and stimulating soundscapes. Jo and Jeon [56] investigated visual environment reproduction employed in VR induces alterations in individuals’ perceptions is also a topic of study. Jo and Jeon’s [58] research is also being conducted on individuals’ preferences for soundscapes and their ability to categorize sounds in a VR. Llorca et al. [93] conducted a study to understand the objective and subjective parameters of acoustic urban heritage conservation. Focusing on the city squares, this study explores the distinctions between the real and virtual worlds. Kern and Ellermeier [51] investigated audio in VR. The authors focused on the effect of stepping sounds on people’s sense of presence in the virtual environment.

In summary, the reviewed studies demonstrate the growing interest in studying the interaction between visual and auditory components in virtual urban environments. Detailed analysis of the role of visual and auditory components in human perception is an important research area that will guide many future VR studies. Most research emphasizes the mutual influence of auditory and visual stimuli on environmental perception, with particular emphasis on natural elements such as vegetation and water. While methodological approaches vary, a common focus emerges: the use of immersive technologies to understand the multisensory urban experience.

3.1.3. Restorative Effect

Most of the disciplines involved in studying the physical changes in the environment and the effects on individuals are shifting their approach. They are moving away from focusing only on negative aspects like pollution and harmful effects and instead adopting a more positive approach that includes studying things like soundscapes and using multiple disciplines such as restoration and well-being [94]. A significant amount of research on VR in urban acoustic environments focuses on the restorative effects of stress recovery. These studies examine how the restorative effect observed in physical environments, such as natural parks, urban parks, green areas, and forests, is also observed in a virtual environment.

Investigating the restorative effect in a virtual environment is important for groups who may experience the restorative effect of natural surroundings through illness or various disabilities. Understanding the boundaries of the restorative impact in virtual worlds will facilitate the application of VR technology for medical purposes.

The restorative effects involve investigating and studying the mechanisms and reasons behind the enhancement of human psychological health, physical health, and general well-being through interactions with natural surroundings. In order to comprehend the ways in which restoration occurs through environmental experiences, there are two prominent theories: attention restoration theory (ART) [95] and stress recovery theory (SRT) [96]. The Perceived Restorative Characteristics Questionnaire (PRCQ) is another questionnaire derived from ART. It was used to measure four perceived restorative characteristics (fascination, novelty, escape, and coherence) [97]. The Perceived Restorativeness Soundscape Scale (PRSS) has been developed to measure the restorative effect in the soundscape framework [98]. These theories have a common belief that natural areas offer psycho-physiological restoration for city dwellers.

Distinct methodologies are used to examine the physical and psychological restorativeness in studies on VR. Physical restorativeness effect measured by Skin Conductance Level (SCL), Skin Conductance Response (SCR), Electrodermal Activity (EDA), diastolic blood pressure, Heart Rate (HR), Heart Rate Variability (HRV), and salivary cortisol. Physiological indicators such as SCL and SCR have been measured in most studies [23,28,44,79,80]. Additionally, some studies evaluated affective changes before and after stimulation using the Positive and Negative Affect Scale (PANAS) [79].

The topics of restorative effect and VR can be categorized into four primary themes. The first theme includes analyzing restorative effects and virtual reality environments and testing basic measurement methods; the second theme includes the investigation of natural audiovisual components; the third includes the investigation of various technologies; and the fourth includes the examination of individual differences.

Table 2. Studies on restoration effect: number of participants, physical and psychological factors, and themes identified.

Themes	Authors	Participants	Physical and Psychological Factors
Basic methods	Annerstedt et al. [37]	30	Cardiovascular data and saliva cortisol data, The Trier Social Stress Test (TSST)
	Park et al. [22]	32	HR, RR, EDA, fEMG-CS, fEMG-Zygo, PRSS
	Meuwese et al. [55]	57	Epidemiological Studies Depression Scale (CES-D)
	Ünal et al. [67]	23	PRCQ (fascination, novelty, escape, and coherence)
	Ojala et al. [69]	39	HRV, PANAS
	Ch et al. [70]	20	The Remote Associates Test (RAT) and the Alternate Uses Task (AUT)
	Mioni and Pazzaglia [73]	52	The Self-Assessment Manikin (SAM), The Subjective Time Questionnaire (STQ), PRCQ
	Kawai et al. [84]	84	NCPCT = Necker Cube Perspective Change Test; SCL = skin conductance level
Natural Audiovisual Components	Hedblom et al. [23]	117	SCL
	Masullo et al. [61]	48	ART(Fascination, Being-Away, Extent and Compatibility)
	Ha and Kim [62]	319	RSS and the Short Form of The Profile of Mood States (POMS-SF)
	Hsieh et al. [71]	45	HR, Total autonomic nerve activity (SDNN), Sympathetic (low frequency-power, LF), Parasympathetic (high frequency-power, HF), Low-to-high frequency-power ratio (LF/HF)
	Gao et al. [75]	50	Short-version revised restoration scale(SRRS)
	Jeon et al. [76]	60	HRV and Electroencephalogram (EEG) PRSS
	Meng et al. [79]	90	SCL and Significant Skin Conductance Responses (nSCR), PANAS
Various Technologies	Hedblom et al. [44]	154	SCL, Visual, Auditory, and Olfactory pleasantness
	Li et al. [59]	30	HR, HRV, HF-HRV, α-EEG, ST, β-EEG and RR
	Weibel et al. [74]	107	Heart rate variability biofeedback (HRV-BF)
	Chen et al. [80]	171	HRV, HR, and SCL, POMs dimensions Scores
	Kari et al. [85]	62	The ROS (Six-item Restoration Outcome Scale), SVS(Subjective Vitality Scale), PANAS, and SSI (stress-symptoms item)
Individual Differences	Senese et al. [26]	95	ART (Fascination, Being-Away, Extent, and Compatibility) NEO Five-Factor Inventory
	Bazrafshan et al. [27]	60	EDA, Questions related to place attachment
	Long et al. [28]	29	SCL, HR, HRV, EDA, Respiratory rate (RF), and Blink frequency (BF), Emotional level, and attention

summarizes these four themes and the physical and psychological measurement methods used.

Experiencing the restorative effect in virtual environments has significant potential for application in various contexts. Experiencing the restorative effects in VR holds significant potential for various applications. The studies in the first theme aim to investigate the specific circumstances and mechanisms in which the restorative effect is pronounced in virtual environments. Annerstedt et al. [37] investigated the effect of nature sounds on stress recovery in virtual natural environments. It shows a potential link between nature, nature sounds, and stress recovery and demonstrates the potential importance of VR as a tool in this area of research. Ünal et al. [67] investigated the restorative effect in the virtual environment by comparing the urban and the garden environments. Additionally, they discovered that there were no significant differences between the real and virtual gardens in terms of perceived restorative characteristics. The restorative effect is mainly focused on urban green areas. Restorative effects are experienced visually and audibly [69]. Therefore, it is necessary to go beyond VR simulations that only visually immerse us in green areas. But also perceiving sounds that have a recovery effect on the auditory. Therefore, the investigation of natural visual and aural components that have a restorative effect in the virtual setting has an important place in these studies. Park et al. [22], Mioni and Pazzaglia [73], and Kawai et al. [84] showed that green areas have a greater restoration effect when compared to urban areas. The studies assessed physical and psychological factors and found that exposure to a green area after experiencing a stressful situation resulted in a reduction in stress and a restorative impact. Meuwese et al. [55] similarly discovered that observing green areas can enhance mood and reduce stress in those exhibiting depressive symptoms. In their study examining green spaces in urban areas, participants exhibiting more depressive symptoms had a more significant reduction in stress after observing natural settings compared to urban areas. The findings indicate that nature-based therapies may be more advantageous for individuals experiencing depressive symptoms. Ch et al. [70] investigated that during the stressful period like COVID-19, when access to natural environments was limited, a daily exposure of 10 min to virtual reality nature and mindfulness practices enhanced certain facets of well-being and creativity, reducing some adverse effects of remote work. Ojala et al. [69] similarly observed that all virtual nature breaks increase stress relief and that breaks in offices are beneficial for employee relaxation and stress management.

The second theme focuses on the change in natural audiovisual components inside a virtual setting, as well as research targeted at understanding the restorative effect. The studies included changing content believed to have both visual and auditory restorative characteristics and then measuring their effects. Regarding visual components, the main emphasis was on the quantity of green elements, the green-blue ratio, and the water element. As for auditory components, the primary attention was on the restorative sounds of birdsong and the sound of water [44,61,75]. The research conducted by Hedblom et al. [44] gives an illustration of the combined effect of visual and auditory stimuli in promoting restoration and reducing stress. The study highlighted that birdsongs not only have a stress-reducing impact; however, it is concluded that this effect is complex, especially related to the presence of green areas observed in 360-degree video, dBA level, and personal factors. Masullo et al. [61] discovered that the presence of green and blue elements enhances our auditory perception and enhances the restorative effect. Goa et al. [75] evaluated the effects of water span and number of building levels on restorativeness, safety, and overall experience (comfort, satisfaction, and preference). The study discovered that the wider the water span, the lower people’s perception of safety, and the overall experience also showed a strong negative link with the number of building levels. The restoration benefits of including birdsong in a waterfront high-level building environment are better than stream sounds. Hsieh et al. [71] emphasized that the impact of different water sound levels on psychological and physiological health remains unclear. In their study, they used a VR natural environment combining forest scenes and waterfall sounds to compare the effects of low and high water sound levels on individuals’ psychological (emotional quality of place and state anxiety relief) and physiological benefits (heart rate variability). Results showed that both low and high decibel levels improved the psychological dimension and lowered the heart rate of individuals with anxiety. In addition, high decibels served to arouse emotions, while low decibels were more effective in calming emotions and relieving anxiety. Natural waterscape sounds were found to alleviate transient anxiety states and support healthy autonomic nervous activity. Jeon et al. [76] conducted a comprehensive VR experiment to examine the restorative effects of urban, waterfront, and green environments. The restorative effect is investigated with questions directed to the participants on audiovisual and measurements made. From reference [76], it can be seen that the restorative effect of waterfront areas is higher. As a result of the study, visually attractive and spatial natural landscapes and acoustically supportive and tranquil soundscapes should be created to improve restoration response. Meng et al. [79] and Ha and Kim [62] investigated the effects of biodiversity on the restorative effect in their study. Their study underscores the stress recovery benefits of high-value ecological environments, while also emphasizing that the existence of biodiversity increases the restorative impact.

The third theme focuses on investigating the rejuvenating impact achieved through the utilization of various technologies, multimodal methods, and conceptual frameworks. Masullo and Maffei [93] discuss the field of experimental reality (ExR) and technological advancements that enhance the credibility of all aspects of their work. Hedboom et al. [23], in their study investigating the effects of the multisensory stress recovery effect, chose the urban area, park, and forest area as the study area. The effects of visual, sound, and smell were investigated. As a result of the study, they concluded that sound and smell are more effective than visual cues in reducing stress. Li et al. [59] aimed to identify changes in physiological indicators and subjective restorativeness in response to audiovisual interactions with a virtual natural environment. Four scenario types were presented in four distinct modalities (video–audio, image–audio, audio-only, and video-only), with each modality assessed by an independent group. Physiological responses and subjective restorations of volunteers were examined to evaluate interactions between audiovisual modalities. The use of static images and sound to reproduce the natural environment evoked greater physiological comfort and subjective restorativeness. Weibel et al. [74] investigated the impact of various technologies and breathing techniques in a virtual natural environment. Specifically, VR demonstrated superior immersion and motivational effects compared to traditional displays; nevertheless, the utilization of an HMD enhanced cardiac compliance more significantly than a desktop screen. In another comparable visual display analysis, Chen et al. [80] tested the restorative effect of green spaces in CAVE. In their study, they investigated the effects of using different technologies and labs and compared urban and green areas. The restorative effect was also observed in the CAVE in their study. Further advancements will be made in the future in this field, encompassing various technologies and diverse measures. Kari et al. [85] examined the impact of three distinct environments (monitor, HMD, and a virtual room) on restoration and stress levels. Consequently, in comparison to the monitor condition, both the HMD and the virtual nature room condition demonstrated a superior impact on psychological states associated with total stress recovery, as seen by greater increases in restoration and subjective vitality. No statistically significant changes were seen between the HMD and virtual room conditions across any of the parameters.

The last theme focuses on individual differences. Due to the variability of the restorative effects, they can differ based on various character traits, cultures, or age groups. Senese et al. [26] analyze the impact of personality traits and water masking installations on the perceived restorativeness of an urban park using the multisensory immersive VR (M-IVR) methodology. In their study, the personality traits were assessed using the NEO Five-Factor Inventory scale, and the restorative effect was assessed using the Perceived Restorativeness Scale (PRS-11). Water installations were associated with an increase in perceived restorativeness (the components of fascination and being-away), but the effect was reduced by personality. The research claims that the favorable impact of water-based features on the assessment of urban green parks is also associated with personality traits. Bazrafshan et al. [27] also investigated the effect of personality traits on relaxation in urban parks. Using virtual park visits, they aimed to find out whether place attachment and familiarity with parks are related to physiological responses, i.e., relaxation/arousal. The study concluded that place attachment and familiarity with a park’s cultural background have a significant impact on emotional responses, especially relaxation. In addition, some empirical evidence has been found that measurable place attachment develops in new places of residence among bicultural migrants. Long et al. [28] examined restorative effects on the elderly individuals residing in nursing homes. It is crucial for those lacking access to urban green areas to have the ability to virtually experience this influence. The study examining videos with and without audio found that silent videos elicited feelings of loneliness and isolation among participants. The study concluded that audio plays a crucial role in the restorative effect, and VR can be a valuable tool in these studies.

The analyzed research demonstrates that the vision and sounds of nature are particularly beneficial in reducing stress, encouraging psychological relaxation, and improving environmental awareness in VR experiences. Audiovisual integration significantly influences perceptual, physiological, and emotional responses. These findings support the assessment of virtual reality not merely as a simulation instrument but also as an aid to individuals’ recovery.

3.1.4. Ecological Validity

Ecological validity has been a prominent theme for VR studies in recent years. Ecological validity refers to the degree to which the findings from a controlled laboratory experiment are applicable to real-world situations [99]. The laboratory should closely resemble real-life conditions when considering the context of the questioning being asked. The selection and presentation of the test samples should be performed in a manner that allows for the reactivation of cognitive processes that have been developed in real-life settings [100]. The concept of ecological validity was first introduced to evaluate the results of a laboratory experiment studying visual perception [101]. After the research in the field of cognitive and behavioral psychology, ecological validity has become a topic of study in many other fields.

Ecological validity is an essential component of the validity of studies conducted in virtual environments. The limited immersion experienced in the laboratory can result in low ecological validity, which in turn can restrict the generalizability of the acquired results [33]. Ecological validity is achieved when a sense of plausibility (Psi), illusion of place (PI), and reactions to a virtual environment occur simultaneously [102]. PI is an intense illusion of being in a particular place, despite the certainty that you are not. The visual and auditory tools we employ have been enhanced by technology, which has made it simpler to create the PI. Psi is the deception that the scenario being depicted is really occurring. It is more challenging to ensure plausibility in this context and to assess it in research [103]. Psi should be performed in a way that allows subjects to recognize and respond to the test samples as natural or possibly familiar experiences. These illusions, manipulating participants’ perception of reality in a VR simulation to align with the qualities of reality, have the potential to enhance the ecological validity of an experiment. This approach brings us closer to reproducing real-life scenarios [104]. These two concepts result in the development of real behaviors in virtual environments.

The ecological validity in urban studies is that they involve high environmental inputs, which makes it more challenging to conduct realistic assessments. In urban studies, conventional laboratory-based experiments offer control over experimental conditions or factors; however, they frequently lack ecological validity as a result of the absence of a real-world context. By contrast, on-site studies like surveys, soundwalks, or interviews can preserve context but are unable to control variables [83]. For this reason, ecological validity is consistently the main topic of research in urban virtual reality that is conducted with a variety of methods, tools, and contexts.

Studies on ecological validity, which examine the real-world applicability of research findings, began with the use of IVR technology in urban areas. The extensive utilization of visualization tools such as computer-aided design (CAD) and a 360-degree camera, along with graphic representation technologies, has facilitated these investigations. Upon reviewing the research conducted in this particular area, one of the significant studies on the combination of visual and aural components in a virtual environment is the research undertaken by Maffei et al. [25]. In their studies, they applied the same questionnaire to the participants in the IVR and the real environment. A series of questions was made regarding the auditory and visual components, and the participants’ overall evaluations for environmental quality, pleasantness, calm, and vivacity scales were compared. Following the questionnaire results, there was no noticeable difference between the virtual and real worlds. This finding partially addresses the issue about the validity of urban acoustic research performed in virtual reality. Puyana-Romero et al. [40] conducted a comparative analysis of field surveys, online surveys, and IVR surveys. They used a 360-degree camera and selected three different urban areas. The data analysis indicates that there are no statistically significant variations in the outcomes of the three modes of multisensory experience. Dongas et al. [72] proposed the virtual urban field studies (VUFS) system for use in urban studies. VUFS is a human–computer interaction approach, and they identified and tested ways in which the immersive possibilities of virtual reality (both perceptual and psychological) can be used to provide an ecologically valid testing environment. Gök Tokgöz and Altinsoy [105,106] conducted a study that also concluded there was no significant distinction between surveys conducted in real and VR. They tested the ecological validity of the soundscape questionnaire in a traffic-heavy area and in a green area. The study was conducted with a limited group of participants and tested in a lab environment, not IVR. Yang et al. [83] investigated the ecological validity of virtual environments in soundscape research, specifically examining the authenticity of virtual audio–visual environments for repeatability. A comparison was made between several technologies used for creating and reproducing virtual environments. These technologies included field recording, VR, AR, and audio-only presentation. The comparison was conducted in two different audio–visual reproduction settings: a head-mounted display with head-tracked headphones and a virtual reality lab with head-locked headphones. At the end of the study, on-site evaluations provided higher pleasantness scores than all other methodologies. The selection of audiovisual reproduction techniques had no substantial effect on the assessments.

Ecological validity in urban areas can be assessed through audiovisual surveys, as well as through other measuring methodologies employed in studies. Ünal et al. [67] investigated the validity of their questionnaire’s restorative effect in real and virtual environments. They discovered that there were no significant differences between the real and virtual butterfly gardens in terms of perceived restorative characteristics. These findings indicate that virtual reality could be a reliable method for researching restorative environments. Jaalama et al. [63] compared the walking experience in the urban park and VR. The area was created using a 3D geo-visualization method, and the study is mainly focused on investigating the effects of it. The VR environment yielded positive outcomes in terms of participants’ exploration of the park area and their perception of objects inside it.

Ecological validity is an issue that needs to be investigated especially in studies with many inputs and actors, such as urban studies. It is important to verify whether each study reaches reliable conclusions within its own dynamics. In this context, ecological validity has an inherent relationship to the technological processes of material production and reproduction, as these directly determine how closely experimental conditions resemble real-world experiences. The studies indicate that virtual settings that possess a high level of realism have the potential to be valuable for future investigations and development. However, in complex subjects involving multiple actors, such as urban studies, attaining realism in all aspects might provide a challenge. Hence, it is crucial to increase the amount of research conducted in this domain and establish ecologically valid measures that align with the study’s objectives.

3.2. Experimental Setup

Recently, due to technological advancements, there has been a broad increase in research using audio and visual reconstructions in urban areas. Understanding the objectives and field selections of these investigations is as important as acquiring knowledge about the tools and strategies employed. This section of the review paper will analyze the audiovisual production and display techniques, experimental settings, and questionnaire-based evaluations used in these studies.

Audiovisual settings are examined through two categories: first, the methods of acquiring the materials, which involve the production of visual and audio content; and secondly, their utilization in experiments, as well as the methods of representing them in a virtual environment. This section was titled “Visual and Audio Display Technologies”.

3.2.1. Production of Visual and Audio Content

The visual and audio representation refers to the initial steps of audio and video preparation in virtual environment studies. The equipment and techniques employed in these initial stages may differ depending on the specific goals of the research, but they play a crucial role in different aspects of the research.

Table 3. Studies on production of visual and audio content.

Production of Visual Content
Photo and Video recording	3D software
Photo [23,42,44,79]	Google SketchUp [10,11,13,15,25,35,64]
360-degree video [3,14,18,20,22,27,28,40,45,48,50,57,66,71,72,76,78,80,82]	3ds Max [26,61,65,67,68]
	Unity [5,13,41,43,51,54,77,83]
	Unreal Engine [26,61,64]
	Bryga 3D [63]
	Rhinoceros 3D [21]
Production of Audio Content
Binaural recordings [14,21,22,23,25,35,42,45,51,65,66,106]	Auralization [5,11,13,41,43,54,64,67,68,77,83]
Ambisonic recordings [3,20,27,28,48,57,72,76,82]

categorizes the production of visual and audio techniques employed in the examined research.

• Production of Visual Content

Visual aspects form a large part of our perception of the environment. Visual representations can be categorized into two main categories. Real-life recordings, such as videos and photographs, and three-dimensional visualizations created with the help of software.

The content comprises real-life recordings, photographs, videos, and especially 360-degree videos. There is a smaller number of urban initiatives that exclusively utilize photographic content compared to those that utilize video. The reason for this is that video has a greater capacity to capture and convince the participants. Video material is easier to obtain than 3D visualizations generated using software.

The 360-degree camera has recently become the most commonly utilized instrument. Figure 5 shows different commonly used 360-degree cameras. 360-degree videos, often known as immersive or spherical videos, enable users to view their surroundings in all directions [107]. The use of 360-degree cameras in urban research provides participants with a fully immersive and participatory experience. When 360-degree videos are observed using a VR platform, the viewer becomes fully engaged in the depicted surroundings with limited interaction with the real world.

Such 360-degree cameras provide a more realistic impression of the depicted area compared with photographic images. Due to recent technological improvements, this research approach is increasingly reliable and easily available, opening up new possibilities for studies [108]. Besides these advantages, 360-degree cameras also have disadvantages. Editing the visuals poses more obstacles and can induce a sense of cyber sickness in users.

Creating three-dimensional visualizations is a more time-consuming choice. Nevertheless, it offers benefits such as the ability to explore other options for planning and making modifications easily. These 3D-simulated visual environments can be produced using various software tools such as 3ds Max, Google SketchUp, Unity, Unreal Engine, Rhinoceros, and WorldViz. The software generates 3D scenes that are extensively utilized in urban planning and design research. Nevertheless, due to the detailed individual control required in each aspect, achieving precise and realistic auralization and visualization in these studies is challenging [64].

• Production of Audio Content

Urban acoustic environments include a variety of sound sources, such as transportation, biological, and human sounds. Various sound sources display different acoustical characteristics and convey distinct meanings. In recent years, the soundscape approach has been utilized to evaluate the acoustic environment in urban settings. Unlike traditional environmental noise approaches, the soundscape approach does not exclusively prioritize the reduction in sound pressure level (SPL). Instead, the soundscape perspective considers sound as a valuable resource rather than something to be eliminated, and takes into account people’s overall sense of the acoustic surroundings [109]. Within the scope of this review, the production of audio content, including sound recording and reproduction, will be explored.

The main recording technologies utilized in investigations include mainly binaural and ambisonic. The ISO/TS 12913-2 also introduced these two recording techniques. Binaural recording is an expanded version of stereo recording. In an ideal scenario, a binaural recording exclusively records the sound that is received at the left and right ear positions. Thus, binaural recording is the format that most closely replicates human hearing when played through accurately calibrated headphones [31]. Due to this reason, it is extensively utilized in the field of urban studies. The various configurations for binaural recording can be categorized into four primary types: (1) binaural microphones placed inside the ears of human listeners; (2) microphones positioned in a dummy head with a torso, head, and ears; (3) microphones located in a simulator with a head and ears; (4) microphones situated in a simulator with only ears. Binaural microphones are miniature devices used for recording sound in human ear canals. They can be professional or low-cost, and some are integrated into headsets. Dummy heads, consisting of a torso, head, and ears, are used in academia and industry to obtain consistent results. Examples include KEMAR, manufactured by GRAS, Brüel & Kjaer 4128 HATS, and Head acoustics HMS IV.

Ambisonic recording is a technique used to capture and play back audio in a complete 360-degree surround sound format. It is a surround sound format that does not specify the playback arrangement, unlike other surround sound recording formats. The system can produce complete surround sound, including the perception of height and depth, using only a single point source in space. Figure 6 shows a selection of the ambisonic microphones utilized in the research.

Most studies that have used audio and visual data from urban areas have used ambisonic recordings. Audio records are especially preferred for the analysis of urban areas, restorative effects, and ecological validity. The auralization method has been utilized in urban design studies, particularly those that involve 3D models.

Auralization is the process of generating audible sound files from numerical data, which can be simulated, measured, or synthesized [110]. Auralization has greater challenges in urban areas due to the complex structure and variety of resources. Llorca-Bofí et al. on creating audiovisual reality in planning provide an overview of what physical principles can already be simulated in their work, what technological aspects need to be taken into account, and how to set up such an environment for the auralization of urban scenes [111]. Schäfer et al. conducted a study on the propagation of noise from aircraft in urban environments. It is an important study as it is an attempt at auralization in the urban area and a guide in this field [112]. Auralization is a crucial procedure for urban studies that specifically aim to evaluate acoustics.

3.2.2. Visual and Audio Display Technologies

The visual and audio display technologies part comprises the instruments utilized in conducting the experiments. The utilization of these tools and emerging technologies also has an impact on the quality of the experiments.

• Visual Display Technologies

Visual technologies can be identified into four groups: monitors, large screens and 2D projection, HMD, and CAVE systems. Various display technologies possess distinct advantages and limitations.

Practically accessible monitors provide effortless and numerous installations for VR research. Experimentation with monitors remains common in the present day. Monitors are often preferred for tasks that require high precision and detail. However, because of the limited size of the monitors, the immersive experience of VR is diminished. Large screens, 2D projections are also basic and effortless tools utilized in the conduct of VR experiments. Large screens or 2D projections provide a more immersive experience due to the wider field of view. They are ideal for situations in which numerous individuals need to access the information at the same time. Although large screens or projections offer a broader visual perspective, the use of HMDs allows individuals to freely move their heads in various directions and perceive different scenes. Consequently, the HMD environment is commonly regarded as more immersive and closely mimicking real-life experiences. Initial research findings indicated that there was no statistically significant difference between the use of HMD technology and large screen and projection conditions [113]. Due to this argument, the use of large screen projection screens was perceived as a cost-effective substitute for HMD technology. However, in recent times, HMD technologies have also gained popularity and have become more affordable. Based on the studies, HMD was the most commonly used visual reproduction method for VR environments [56].

The commercial emergence of HMD occurred in the early 90s; its broad use began in the 2010s and continues to the present [114]. HMDs provide a heightened level of immersion, generating a powerful feeling of being there within the virtual environment. They offer a regulated environment and benefit from the ability to guarantee reproducibility. HMD facilitates interactivity and fosters user engagement. Furthermore, improvements in HMD technology have rendered these devices more cost-effective and convenient, hence increasing their availability and accessibility to a broader range of users across various research environments. Although the HMD provides a comprehensive visual experience by fully covering the field of view, it might impact movement and posture due to the additional weight it places on the head. Additionally, it is possible that it will experience symptoms of dizziness and cyber sickness [115]. These challenges can be mitigated by systematically evaluating the conditions of HMD usage and carefully planning the period of exposure.

In addition to these technologies, the CAVE system is also utilized. The CAVE system was first introduced in 1992 [116], and the purpose of its creation was to offer a one-to-many visualization experience that makes use of large projection screens. A comparable approach with large projections is Progetto Sipario. The Sipario project is intended for the recording and immersive replay of opera performances utilizing 3D audio and 360° video in private listening environments [117]. Progetto Sipario or Sipario project shares visual similarity to the CAVE technology; nevertheless, its use has been customized for opera and theatrical performances [118]. While user interactivity is more advanced in CAVE systems, Progetto Sipario merely allows the user to listen and see the performance. Findings indicate that depth perception in CAVE was better than that in the 2D projection [119]. This suggests that the immersive environment provided by CAVE enhances the perception of virtual space. The CAVE offers the advantage of enabling multiple individuals to interact simultaneously with the environment and participate in social interaction. Limitations of a CAVE system include its vast physical size, the expensive high-resolution projectors, and challenges with human–computer interaction.

HMD technology is often addressed in the literature [10,14,25,28,36,44]. Given its ability to give a more realistic 360-degree imagine experience and its increasing accessibility in recent years, this outcome is consistent with expectations. After the HMD, VR investigations generally choose more easily accessible and commonly used monitors [12,15,22,53,64]. Large screens, projectors [83,106], and CAVE [17,38,52,67] systems are less preferred due to cost and space requirements.

• Spatial Audio Reproduction Technologies

Spatial audio reproduction covers the techniques, devices, and systems employed to accurately replicate or recreate sound from recorded or generated audio sources. Spatial audio, commonly referred to as three-dimensional (3D) audio, pertains to the way sound is perceived in a three-dimensional space and encompasses all aspects linked to this perception, such as sound capture, creation, mastering, processing, reproduction, and evaluation [120]. This section focuses on spatial audio reproduction, i.e., how recorded or generated audio is delivered and perceived by the listener. Recording and production techniques, though related, are treated as complementary but separate domains and are discussed elsewhere in the manuscript.

With the advancement of reproduction techniques for spatial audio, researchers have begun incorporating them into their investigations. The spatial audio reproduction techniques are essentially categorized into two groups. The first category employs the method of physically reconstructing sound, with the goal of synthesizing the complete sound field in the listening region to closely resemble the target signal. The second category is related to the perceptual reconstruction of sound to generate a perception of its spatial characteristics.

The objective of physical sound reconstruction is to replicate the sound field in the listening location to closely resemble the ideal sound field. Stereo configuration and multichannel reproduction are commonly employed techniques for physically reconstructing sound. Wave field synthesis (WFS) and ambisonics are two additional physical reconstruction techniques that attempt to recreate the same acoustical pressure field that exists in the surrounding environment. WFS was proposed with its first major commercial application demonstrated in 2001. In 2011, IOSONO came up with the world’s first real-time spatial audio processor for WFS. First-order Ambisonics (FOA) can be represented in different formats, such as A-format (e.g., four cardioids in a tetrahedral configuration) or B-format (one omnidirectional and three figure-of-eight channels). Both formats are used in Ambisonics representations. A significant advantage is the ability to modify the pan, tilt, zoom, and rotation of the sound field through post-processing, a task that is challenging to accomplish with alternative systems that depend on the original collection. The main limitation of first-order ambisonics is its restricted spatial resolution, which adversely impacts sound localization and is only efficient inside a somewhat confined sweet spot. In order to enhance the performance of first-order ambisonic, higher-order ambisonic employs additional microphones to capture the sound field at higher degrees [31]. While Higher-order Ambisonics (HOA) systems can be more costly than FOA, commercial solutions are already available (e.g., Eigenmike EM32, EM64), and more accessible multi-microphone arrays also exist (e.g., Zylia ZM-1). In addition, upscaling techniques allow FOA recordings to be transformed into HOA to improve spatial resolution.

Perceptual reconstruction approaches for spatial audio strive to recreate the authentic listening experience by producing adequate audio cues that accurately represent the real sound. The binaural technique is a collection of approaches that utilize auditory input signals to both ears of the listener. These signals are then analyzed, synthesized, processed, presented, and evaluated. Head-related transfer functions (HRTFs) quantify the alteration in the sound spectrum resulting from the interaction between sound waves and the listener’s body, head, and auricle. Spatial audio reproduction for VR/AR frequently includes binaural rendering with head-tracking. However, it is also possible to use multichannel playback systems with an ambisonic decoder. Playback Technologies encompass the various devices and systems employed to replicate and provide audio content for the purpose of listening. These technologies encompass a broad spectrum of hardware and software that transform recorded or streamed audio information into audible sound. Speakers and headphones are devices used for audio playback hardware in the studies.

3.2.3. Experimental Environment

Manipulating the participants’ perception of reality in a VR simulation to align with the qualities of the actual environment has the potential to enhance the ecological validity of an experiment. This approach brings us closer to replicating a real-life scenario while avoiding the major limitation of a lack of control. Apart from audio–visual technologies, the experimental setting is also crucial for conducting tests that closely simulate real-life scenarios. Acknowledge your limitations when conducting experiments in the laboratory. This is especially true when it comes to contextual factors. The equipment utilized in the experiments must be carefully developed to align with the planned objectives.

There are several laboratory environments that are adapted to the specific characteristics of audio and visual display systems, as well as specialized VR laboratories. Figure 7 shows the various laboratory settings.

According to the analyzed research, most VR experiments showed a preference for using HMDs and headsets. The attributes of the laboratory setting are inconsequential in these tests. The lack of background noise is a sufficient requirement. Semi-anechoic chambers are commonly used for particular investigations as experimental settings for eliminating background noise. Furthermore, there are also specialized VR laboratories established for the purpose of conducting VR experiments. These laboratory environments consider elements such as the acoustic and visual aspects of the experimental setting and the sense of immersion.

The CAVE is a commonly used VR experiment; however, it has only been utilized in a limited number of studies. The urban VR research is also utilizing multimodal labs, which include senses beyond auditory and visual. Each of these laboratory environments possesses distinct properties that are crucial for the advancement of research. These multimodal labs can include additional physical characteristics such as tactile [121] smell, temperature, or air quality in their studies.

3.2.4. Questionnaire-Based Evaluation

The studies use a variety of methodologies, including soundwalks, questionnaires, and interviews. The data on user perception are examined using both qualitative and quantitative methodologies. Upon analyzing the VR research conducted on urban areas, it becomes evident that the questionnaire is the most frequently employed.

Questionnaires are an important part of VR studies on urban areas. Although studies are conducted for different purposes, user perception is important in all of them. By analyzing the questionnaires utilized in the research, we may categorize them into different groups, such as questionnaires assessing the auditory environment, the visual environment, and questionnaires evaluating comfort in the virtual environment.

There are differences in the acoustic environment assessment questionnaires across different research. There are studies that specifically examine annoyance, studies that investigate particular sounds perceived in VR, and several studies that utilize the questionnaire and adjective pairs outlined in the soundscape approach. The defined procedures, questionnaires, and evaluation methods constitute the basis for assessing the acoustic environment within the soundscape approach [92,122]. The defined procedures, questionnaires, and evaluation methods of urban design and planning studies primarily examine the feeling of annoyance, whereas research analyzing urban environments, particularly those emphasizing the audiovisual interaction, employs the soundscape approach. Whenever conducting research on the restorative effect, it is preferable to prioritize questions that specifically address the restorative effect of sound. Furthermore, other inquiries, such as PRSS, have been formulated regarding the restorativeness. Research on ecological validity investigates whether sound sources are perceived similarly in real and virtual environments. Questionnaires regarding the acoustic environment are evaluated in both settings [105].

Questions regarding the visual environment are also addressed in the studies. These questions could relate to the quality, reliability, pleasantness, or subjective response to the visual environment. Considering the established influence between visual and auditory stimuli [4], this research specifically focuses on identifying the visual aspects that affect our perception of audio. Research in this field has also explored the impact of visual display technology on our perception. The role of visual perception is significant, and therefore, it is necessary to examine the physical attributes of display technologies, including their quality dimension.

4. Discussions

This study aimed to improve comprehension of VR investigations that specifically examine urban environments and urban acoustics. We initially categorized the investigations based on their research goals, which established the basic framework of the study. The diversity in research goals causes differences in field selection and experimental settings. The increasing amount of virtual reality-based urban acoustics research is not yet fully integrated into soundscape investigations. While many guidelines exist for soundscape studies [92,122], none are established for research conducted in VR. Consequently, the methodologies, devices, experimental configurations, experimental conditions, and duration of the experiments are entirely distinct from one another. A comprehensive evaluation helps in identifying and acknowledging the essential deficiencies in the perception and informs future work in this field.

The study first examined research specifically targeted at urban design and planning objectives. By conducting these studies, it is possible to predict and make informed design and planning decisions in urban environments. This is a significant benefit for costly and time-consuming urban design. Conducting these studies in VR is particularly important in urban design and planning, as it allows for public participation and facilitates communication among decision-makers. However, with a closer examination of the research on urban design and planning, it becomes apparent that there is a lack of comprehensive studies on urban acoustics. With the exception of the visual and audio impacts of noise barrier design [41] and new highway planning [10], a large number of studies in this field have not particularly emphasized acoustic design. Despite the advantages of VR for urban design, there is a significant deficiency of research that integrates soundscape-based principles into urban planning.

Urban analysis studies typically aim to comprehend the complementary impacts of visual and aural elements. Research on urban analysis has a crucial role in comprehending the diverse situations of urban areas, their translation into digital, and the constituents of urban areas. This research investigated not only the analysis of audio–visual elements, but also the suitability of the instruments utilized, the change in user perception, and several essential criteria like traffic safety [65]. Furthermore, this research offers valuable insights on how to accurately depict intricate urban areas in VR based on their findings.

Research on the restorative effect is particularly crucial for the development of applications in the domains of health and psychology. Currently, urban areas create a significant strain on individuals, causing stress. Despite attempts to expand the presence of restorative places within urban areas, these efforts often fall short due to the rapid growth of the population and the physical constraints of urban areas. In this regard, conducting these studies on investigating and delivering restorative effects in VR would be beneficial. Furthermore, this virtual restorative effect will improve the treatment and rehabilitation procedures for underprivileged populations, such as the elderly and disabled, who lack actual access to these restorative areas. Restorative effect research in virtual environments has widely examined visual stimuli; the role of sound in creating immersive and stress-relieving urban experiences is still under-researched. Soundscape studies highlight the importance of auditory environments in stress recovery, but more research is needed to understand how VR can simulate these effects.

Ecological validity studies, similar to urban analysis studies, enhance our comprehension of the virtual environment. Therefore, it is crucial to include various VR experiments in ecological validity studies. Additionally, it is necessary to conduct separate research for different locations with distinct acoustic and visual features, as well as for different equipment, laboratory settings, and different data collection methods.

Upon performing a brief assessment of the field selection, it becomes evident that urban green spaces, in particular, take priority. The main reason for this is the analysis of urban audiovisual components and the investigation of their restorative effects. This research corresponds with the soundscape, which frequently links natural acoustic environments to stress relief and improved well-being. Nonetheless, although visual elements have been thoroughly examined in VR-centric urban studies, auditory parameters like the quality of natural sounds, noise masking effects, and perceptual differences are still not properly investigated. Beyond urban green areas, high-traffic areas also emerge as critical study environments due to their problematic acoustic conditıons and potential noise pollution issues. Despite these challenges, the expansion of research to diverse urban settings is necessary to establish a more comprehensive understanding of urban soundscapes.

Technological advancements, particularly in visual technologies, have played a crucial role in the development of VR-based urban studies. The integration of 360-degree cameras in audiovisual production has enabled more realistic VR simulations, fostering a deeper engagement in perceptual and behavioral studies. Additionally, the extensive utilization of HMDs has led to an increase in immersive experiments, allowing researchers to study both objective acoustic parameters and subjective sound perception in controlled VR settings. Notably, VR research has also become more accessible due to advancements in hardware and software, enabling investigations in institutions lacking specialized laboratories such as the CAVE. However, the technological advancements capable of accurately recreating real-world soundscapes in VR remain a challenge. More research is needed to improve spatial audio, enhance sound quality, and understand the psychological effects of these auditory experiences in urban environments.

4.1. Key Challenges

VR-based studies on urban acoustic environments are categorized, with a detailed discussion of challenges in applying VR to evaluate urban soundscapes. One of the primary difficulties in this field is the creation and conduct of ecologically valid studies [123]. Urban areas consist of diverse components, and accurately representing them in terms of sound and visuals is challenging in order to maintain ecological validity. Ecological validity can be influenced by various factors such as the survey employed, the background of the participants, and their relationship with the environment [124]. Furthermore, the main factors to consider during ecologically valid laboratory investigations have been recognized as the impact of memory, the duration of stimulus presentation, and the level of auditory immersion [33]. Hence, it is crucial that care be taken in designing ecologically valid experiments, and the representation should be determined by selecting visual and auditory devices in line with the objectives of the experiments.

One notable challenge in VR applications for urban soundscapes is the limited realism of auditory simulations, which can affect user perception and ecological validity [123]. Recent advances in ambisonic recording and auralization techniques demonstrate that, although ambisonics is a well-established technology dating back several decades, developments in digital signal processing and real-time rendering have significantly improved its practical applicability in immersive audio reproduction.

HMD was the most used visual reproduction method for VR studies. However, another factor to take into account is that the VR headsets are not sufficiently user-friendly. Teaching and explaining its use requires a significant amount of time. Not all individuals simultaneously accept it. That is why a majority of IVR research often indicates that the participant group consists primarily of young individuals [56,57,60,79]. There has been only one study that has given priority to the participation of elderly individuals, specifically focusing on their perceptions [28]. In addition, HMD raises potential health concerns, particularly participant visual fatigue [125], such as eye strain, caused by constant looking on screen or HMD [126], cyber sickness or motion sickness [127,128], physical injury due to unawareness of the real-world surroundings [129], and psychological effects such as emotional desensitization after long-term exposure to VR environments [130]. The following measures to avoid adverse impact on the use of VR should be considered, as suggested in the literature review of Conner et al. 2022 [131]. These issues may be mitigated by developing standardized procedures for VR-based experiments. Regarding fatigue, it is recommended to limit exposure durations, since prolonged use of HMD can increase fatigue and reduce the reliability of responses. It was found that VR experiments should have a maximum duration of 55 to 70 min [132]. To minimize the visual strain caused by VR, it is essential to reduce vergence-accommodation mismatches [133]. Avoiding motion sickness is possible with the observation of the navigation speed and by the quality of the graphics [132,133,134]. The quality of sound, instructions, and in-game prompts also help reduce discomfort and fatigue [132], as well as minimize latency cues, making the virtual environment more immersive [135,136,137]. The prevention of physical injuries during the VR experiment should consider adjusting headset angles [138], improving virtual object placement, reducing the need for large movements, and mapping finger motions to virtual actions [139]. Additionally, providing sufficient play space for users to explore the virtual environment [140] is also important. Moreover, highly immersive settings are not always necessary; in some cases, simpler visual representations may be sufficient to obtain valid results without causing unnecessary distress to participants [141,142].

Unfortunately, this issue is not limited to IVR research and VR headset usage but also extends to studies that involve online questionnaires. Although online surveys provide numerous benefits, they primarily attract younger participants [11]. This was clearly apparent in numerous surveys undertaken during the COVID-19 [143,144]. Consequently, we can contend that numerous emerging technologies and tools do not adequately encompass the entirety of society [71].

Participant bias is also a factor to be taken into account. In multiple experimental settings where different variables are tested, it is problematic if the same participants participate in experiments with similar scenes, especially if the experiments are lengthy and exhausting, or if the participants are the same people in both the field and virtual environment.

4.2. Limitations

This review has several limitations that should be taken into account. The primary emphasis was on outdoor VR applications, which led to the exclusion of indoor studies. Numerous VR studies conducted in urban environments, which include only visual simulations without auditory elements, were not included in the scope of the study. Although these excluded studies may offer valuable perspectives, they did not meet the specific inclusion criteria of this review, which centered on audiovisual integration. Furthermore, technologies closely related to VR, such as Augmented Reality (AR) or Mixed Reality (MR), were not included. These technologies are increasingly present in urban research and can provide important, complementary insights. However, due to methodological, equipment, and experiential differences, a narrower focus was chosen in this study.

This study has primarily relied on qualitative analyses, focusing on basic perceptual responses. Consequently, it does not fully account for more immersive or interdisciplinary approaches to sound, such as those found in ecosophy [145], sound as an object [146], sound morphology [147], acoustic design from the perspective of acoustic territories [148], sound art [149] sound ecology [150], sound ethnology [151], or participatory methodologies [152,153]. Moreover, there is still a lack of studies that combine such multifaceted approaches with virtual reality technologies, which limits the ability to capture the full esthetic, emotional, and cultural dimensions of soundscapes.

A review protocol was not preregistered, which may limit the transparency and reproducibility of the process. And it did not include any formal assessment of risk of bias and publication bias that might affect the certainty of the evidence. This review is also limited by language and database restrictions, as only studies published in English and indexed in specific databases were included, which may have led to the omission of relevant literature. The study systematically reviewed 69 papers. Disciplinary variations led to the emphasis of different aspects in each article, and the diversity in the research objectives, experimental setups, and technological tools used in these studies complicated the establishment of clearer distinctions and comparisons between them. These limitations highlight both the richness and complexity of the field and indicate the need for broader, interdisciplinary investigations in future research.

4.3. Future Directions

Advancements in hardware, artificial intelligence, wireless technology, and mixed reality integration will probably significantly influence the future of urban VR research. These advancements will enhance the utilization of VR in several domains, augmenting the level of immersion, realism, and simplified use. As these technologies progress, virtual reality experiments will become more advanced and provide unique opportunities for research and innovation. The overall number of research conducted in urban areas will correspondingly rise alongside these advancements.

The main source of enhanced immersion and realism is anticipated to arise from VR endeavors. Upcoming HMDs will feature enhanced resolutions, expanded fields of view, and improved ergonomics, resulting in a heightened sense of presence and fewer possible adverse effects. Consequently, there will be a rise in urban VR research. Furthermore, the implementation of haptic feedback technology will allow users to perceive textures, forces, and vibrations, enhancing the realism of virtual interactions. There are also studies that highlight the significance of measuring multimodal experiences and emphasize that not only audio and visual but also fresh air quality are important for the restorative effect in urban studies [79]. The implementation of multisensory experiments will be expanded to incorporate various physical elements such as odor, airflow, and temperature, which play a significant role in urban environments.

In upcoming goals, particularly in the fields of mixed reality (MR) and AR, there will be a rise in the development of hybrid experiences. These experiences will combine virtual and real-world elements to create more adaptable applications [94]. Expected advancements include the integration of artificial intelligence and machine learning. AI will be integrated into VR environments, just as it exists in every area of our lives. AI will greatly assist VR applications, particularly those that generate significant quantities of data and are incorporated into complex systems like urban areas. Consequently, they would possess the capability to generate interactive and customized VR encounters by modifying surroundings and situations instantaneously based on user engagement. Furthermore, machine learning and AI algorithms will enhance data analysis and offer more profound insights into user behavior and experiment outcomes.

Future studies should examine the ways in which virtual reality technology can be effectively integrated with immersive and interactive sound methodologies, such as soundwalks, to produce more complex multisensory experiences. Interdisciplinary perspectives from ecosophy [145], sound as an object [146], sound morphology [147], acoustic design from the perspective of acoustic territories [148], sound art [149], sound ecology [150], sound ethnology [151], and critical sound studies may guide the development of VR applications. They help capture emotional, subjective, and cultural layers of the soundscape in addition to simulating auditory environments. Such approaches would open new possibilities for urban design and planning by integrating both perceptual and experiential dimensions of sound.

VR research in urban environments will continue to expand in the future, encompassing diverse applications across multiple domains. Emerging research on the restorative effect indicates that there will be advancements in this area. Urban design and planning are expanding as a significant educational resource by offering immersive learning experiences and simulations. Future research should explore the integration of real-time data into VR environments to enhance ecological validity. Additionally, interdisciplinary approaches involving urban planners, acousticians, and VR developers could accelerate the adoption of VR technologies in practical urban design.

5. Conclusions

VR representations are becoming increasingly realistic due to technological advancements. Recent developments in VR have significantly improved our understanding of urban acoustics. The advancement and introduction of new methodologies and technologies have contributed to the rise in research in this field. Research conducted across disciplines with diverse research goals has yielded significant insights into the understanding of virtual environments, urban planning, restorative effects, and the distinctions between virtual and physical environments. Extensive research has provided valuable insights into the attributes of the methodologies and equipment used.

A collection of 69 papers was assessed in this study. Each of these research projects has been approached differently based on the study’s objectives, the chosen field, and the employed techniques. Research investigating the combination of audiovisual data in urban areas has primarily concentrated on analyzing audiovisual components in virtual settings. These studies have increased with the advancement of visual recording and display technologies. Furthermore, there has been a shift in the way environmental noise is addressed, with a greater emphasis on user perception and the creation of visually and acoustically pleasant environments. Despite these advancements, several research gaps remain. First, future studies should prioritize the ecological validity of VR-based soundscape research. Improving these elements would provide more precise representations of real-world situations and increase the reliability of experimental results. Following this, research should explore how different demographic groups, such as the elderly, children, and individuals with sensory sensitivities, interact in VR. Considering that perception and comfort levels may differ across different populations, considering these differences would improve the inclusion and relevance of VR-based urban research.

Since VR-based soundscape studies do not yet have a standardized framework like ISO 12913 [92,122], this regulatory gap contributes to the considerable variation observed in devices, experimental configurations, and exposure durations across the reviewed studies. Future work should therefore consider whether the ISO framework can be adapted to VR contexts or whether new methodological standards are needed. Ultimately, the integration of real-time adaptive audiovisual simulations and AI applications should be prioritized to create more dynamic and interactive urban VR experiences. These advances will make virtual settings more realistic and immersive by allowing real-time changes depending on user inputs, hence closing the distance between real and digital urban experiences.

Considering the rapid development of VR and its applications in urban studies, the number of research studies in this domain is expected to grow in the coming years. This review provides a structured overview of existing studies and highlights key areas for future exploration, serving as a foundation for further advancements in urban soundscape research.