Search Results (35)

With the rapid expansion of the aviation industry, pier-style departure lounges have become increasingly prevalent in modern airport terminals. Unlike traditional long enclosures—such as corridors, tunnels, and subway stations—airport terminal piers feature unique geometries, volumes, and interior finishes which complicate sound propagation. To address the paucity of objective acoustic data in these expansive environments, this study performed in situ measurements of impulse responses and sound pressure levels in two piers with distinct shapes and volumes within the same terminal. Key acoustic parameters, including the A-weighted equivalent continuous sound pressure level (L_Aeq), early decay time (EDT), reverberation time (T₃₀), definition (D₅₀), and speech transmission index (STI), were analyzed. The results reveal that EDT and T₃₀ increase significantly with distance from the sound source, while D₅₀ and STI decrease correspondingly. Specifically, compared to Pier B, which has a smaller cross-sectional area and a single-sided layout, Pier A, characterized by a larger cross-sectional area and a double-sided layout, exhibits a faster sound attenuation when the receiver is positioned closer to the source and a longer reverberation time when the receiver is farther from the source. Notably, STI does not differ significantly between the two piers. These findings enhance the understanding of acoustic behavior in large-span, elongated airport piers and provide valuable guidance for optimizing the acoustic environment of departure lounges to improve passenger comfort. Full article

The indoor acoustic climate of dining places often presents challenges for designers and their projects. In this type of enclosure, one of the fundamental factors determining the acoustic climate of a space is the acceptable speech reception in relation to sound alarm systems. This study discusses an index-based method for assessing the acoustic climate of dining places, such as restaurants and cafeterias, during the design process. These studies focused on the reverberation time and speech intelligibility as key parameters defining the acoustical climate. The analyses considered dining places (primarily restaurants) with different dimensions, geometries, and layouts. The method combines architectural parameters (such as volume or shape) and acoustical parameters (such as absorption or background sound) that influence the acoustical quality of dining places. The proposed method is assumed to provide a convenient evaluation of planned dining locations in terms of speech intelligibility. The method is based on the W_R index parameter and serves as a functional tool for architects and designers in their initial drawings and when making design decisions. The method was verified using subjective assessments. Implementing this method provides possibilities to increase the comfort of restaurants and cafeterias and lower or avoid costs associated with improving the acoustic comfort of ready-to-use dining places. Full article

Blowoff limits are essential in establishing the combustor operating envelope. Hence, there is a great demand for practical aero-engines to extend the blowoff limits further. In this work, the behavior of non-premixed swirling flames under fuel flow rate oscillations was investigated experimentally close to its blowoff limits. The methane flame was stabilized on the axisymmetric bluff body and confined in a square quartz enclosure. External acoustic forcing at 400 Hz was applied to the fuel flow to induce a fuel mass flow rate fluctuation (FMFRF) with varying amplitudes. A high-speed burst-mode laser and cameras ran at 20 kHz for OH*-chemiluminescence (CL), CH₂O-, and SO₂-PLIF measurements, offering the visualization of the two-dimensional flame structure and heat release distribution, temporally and spatially. The results show that the effect of FMFRF is predominantly along the central axis without altering the time-averaged flame structure and blowoff transient. However, the blowoff limits are extended due to the enhanced temperature and longer residence time induced by FMFRF. This work allows us to explore the mechanism of flame instability further. Full article

This study addresses the critical challenge of developing lightweight, flexible soundproofing materials for contemporary applications by introducing an innovative Flexible Soundproofing Metapanel (FSM). The FSM represents a significant advancement in acoustic metamaterial design, engineered to attenuate noise within the 2000–5000 Hz range—a frequency band associated with significant human auditory discomfort. The FSM’s novel structure, comprising a box-shaped frame and vibrating membrane, was optimized through rigorous finite element analysis and subsequently validated via comprehensive open field tests for enclosure-type soundproofing. Our results demonstrate that the FSM, featuring an optimized configuration of urethane rubber (Young’s modulus 6.5 MPa) and precisely tuned unit cell dimensions, significantly outperforms conventional mass-law-based materials in sound insulation efficacy across target frequencies. The FSM exhibited superior soundproofing performance across a broad spectrum of frequency bands, with particularly remarkable results in the crucial 2000–5000 Hz range. Its inherent flexibility enables applications to diverse surface geometries, substantially enhancing its practical utility. This research contributes substantially to the rapidly evolving field of acoustic metamaterials, offering a promising solution for noise control in applications where weight and spatial constraints are critical factors. Full article

Attention is a pivotal component and a central vehicle of mindfulness, a psychological factor improving mental health. Despite architecture’s potential to encourage attention and mindfulness, there is still a research gap. This study aimed to investigate architectural design strategies that promotes attention in order to foster mindfulness. The research was carried out in three primary stages. The first step entailed conducting a systematic review by searching publications related to architecture that promotes attention from Scopus in February 2024. After considering the suitability and accessibility, 32 articles were included. No studies were found to have investigated the field of enhancing mindfulness. The second step utilized content analysis to decode the selected articles using a framework developed from literature reviews. All three coders decoded the data independently, allowing the main researcher to compile it into the final dataset. Finally, the data underwent Python meta-analysis for word frequency and association. The result revealed certain qualities that help achieve attention through architecture. The architectural atmosphere is most effective when it features natural forms and spaces that evoke a sense of enclosure. The lighting should emphasize natural light and uniformity, whereas the sound designs primarily concern acoustics, ambient, and noises, with controlled weather emphasizing air aspects. The building should utilize natural materials and incorporate object elements; the facade and entrance are particularly crucial components. Moreover, the colors of brick and green and views encompassing gardens and vegetation are among the qualities mentioned. Based on the analysis, the material, view, and color features were most congruent with the biophilic design concept. All these factors are expected to foster mindfulness, thereby improving mental health. Full article

The acoustic landscape directly affects people’s perceptual experience, which is crucial to enhancing urban greenways’ visibility experience. This study analyzed data from three typical urban greenways in Fuzhou City. By classifying and combining the landscape space into two levels of “enclosure–coverage”, the space was categorized into six types: covered, uncovered, open, semi-open, semi-enclosed, and enclosure space. We explored the characteristics of soundscape perception and the factors affecting the evaluation of soundscape perception in different landscape spaces. The results showed that differences in sound sources between day and night led to differences in the soundscape of different spatial types. The sound pressure level decreased with an increasing degree of enclosure and coverage. The evaluation scores of sound source perception and soundscape perception were significantly different in different degrees of spatial enclosure and coverage, where the open space and covered space were the most sensitive to sound, and the open space played a positive role in enhancing the harmony of the artificial sound. Pleasantness and richness were the main factors influencing overall perception, contributing 50% and 17%, respectively. Visitors’ age, residence type, and visit frequency were the main factors affecting the evaluation of soundscape perception. The conclusions provide a reference and data for improving urban greenways’ soundscape quality. Full article

Bottlenose dolphins (Tursiops truncatus) rely on frequency- and amplitude-modulated whistles to communicate, and noise exposure can inhibit the success of acoustic communication through masking or causing behavioral changes in the animal. At the US Navy Marine Mammal Program (MMP) in San Diego, CA, dolphins are housed in netted enclosures in the San Diego Bay and exposed to noise from vessels, unmanned underwater vehicles, and other remote sensing devices. The acoustic behavior of 20 dolphins was monitored and whistle rates during noise events were quantified. Whistle rates during the onset of the event (i.e., the first 5 min) did not significantly differ from the pre-onset (5 min immediately preceding). Whistle rates were also not significantly different for the entire duration of the event compared to a matched control period. The noise’s frequency range (i.e., control, mid-frequency (0–20 kHz) or high-frequency (21–80 kHz)), signal-to-noise ratio, and sound pressure level were not significantly related to the dolphins’ whistle rate. Considering this is a location of frequent and moderate noise output, these results lend support to established guidelines on anthropogenic noise exposure for cetaceans, suggesting that moderate noise exposure levels may not impact communication efforts in bottlenose dolphins. Full article

A soundscape can enhance the acoustic environment of urban areas and support the sustainable development of green spaces. This study is based on field research on plant information and a perception questionnaire conducted in 30 urban park sample sites in China. The study analysed the differences in soundscape perception among different plant spaces using three dimensions: sound source dominance degree (SDD), sound source harmony degree (SHD), and soundscape perception evaluation. Additionally, five physical indicators of plant space were selected to quantify the effects of physical characteristics of plant space on soundscape perception in urban green space (UGS). The results indicated that there were impacts on soundscape perception. The evaluation of soundscape perception between different types of plant spaces revealed notable differences, particularly in open and enclosed spaces. All eight indicators demonstrated significant differences, indicating that soundscape perception was influenced by the type of plant space. Additionally, there was a significant correlation between plant space and soundscape perception. The evaluation of soundscape perception in three dimensions was related to several factors, including the degree of spatial enclosure, crown density, average tree height, the proportion of trees and shrubs, and the number of tree species. The dominant factor affecting sound source dominance was found to be the degree of spatial enclosure, followed by the average height of trees. Additionally, the diversity of trees affected the overall soundscape perception. Full article

The bullring of Ronda, one of the oldest in Spain, declared in 1993 as an Asset of Cultural Interest, occupies a paramount place among the buildings of its type thanks to its outstanding beauty. Its configuration as an open-air enclosure with a circular floor plan, as an evocation of the ancient Roman amphitheaters, and its interior with galleries on two levels that house the audience play a fundamental role in the acoustic energy decay and diffusion of the space. The link between architecture and acoustics of the Ronda bullring has been carried out by using on-site measurements and simulation techniques. To this end, an acoustic model is created, which is adjusted by taking the set of 3D impulse responses recorded on-site. The presence of the public and the various sound sources that exist during the bullfight itself are analyzed in the simulations, whereby the conditions of occupation and vacancy are compared, as are the variations due to the location of the sources. Finally, speech intelligibility conditions are simulated with a human directivity source. The precision of the virtual acoustic model enables the sound architecture of this singular space to be ascertained and preserved, thereby incorporating sound as an associated intangible heritage. Full article

Active noise control (ANC) is a technique applied to eliminate an unwanted sound by superposing a signal of equal amplitude and opposite phase, sometimes defined as an anti-noise signal, computed through an adaptive algorithm. The study described herein aims to evaluate and compare the performance of some of the most popular algorithms based on the least mean squares (LMS) approach applied to a multichannel active noise control system in a small, enclosed space. The comparison is conducted through an experimental evaluation of the ANC algorithms’ performance, carried out on a tractor cabin in a hemi-anechoic chamber, generating the unwanted sound field using a dodecahedron sound source placed outside the enclosure, emitting narrowband and broadband signals. The experimental analysis and the comparison with the results obtained in a free field condition have made it possible to show certain practical limitations when implementing the algorithms. The results show that the feed-forward systems allow for greater stability, avoiding the acoustic feedback from the control loudspeakers to the reference microphone when this is outside the cabin, while the feedback system is the slowest configuration to converge, requiring an internal modeling of the reference signal. With random signals, the feed-forward systems concentrate their performance in the range above 500 Hz, while the feedback system becomes ineffective. Full article

Bare board AudioMoth recorders offer a low-cost, open-source solution to passive acoustic monitoring (PAM) but need protecting in an enclosure. We were concerned that the choice of enclosure may alter the spectral characteristics of recordings. We focus on polythene bags as the simplest enclosure and assess how their use affects acoustic metrics. Using an anechoic chamber, a series of pure sinusoidal tones from 100 Hz to 20 kHz were recorded on 10 AudioMoth devices and a calibrated Class 1 sound level meter. The recordings were made on bare board AudioMoth devices, as well as after covering them with different bags. Linear phase finite impulse response filters were designed to replicate the frequency response functions between the incident pressure wave and the recorded signals. We applied these filters to ~1000 sound recordings to assess the effects of the AudioMoth and the bags on 19 acoustic metrics. While bare board AudioMoth showed very consistent spectral responses with accentuation in the higher frequencies, bag enclosures led to significant and erratic attenuation inconsistent between frequencies. Few acoustic metrics were insensitive to this uncertainty, rendering index comparisons unreliable. Biases due to enclosures on PAM devices may need to be considered when choosing appropriate acoustic indices for ecological studies. Archived recordings without adequate metadata may potentially produce biased acoustic index values and should be treated cautiously. Full article

The soundscape quality of urban parks can influence the mental and physical health of park visitors. This paper proposes strategies for optimizing soundscape quality by correlating the physical parameters to the human perception. The data has been gathered through a case study of Greenlake Park located in Kunming, China. The objective physical acoustic indexes and the subjective soundscape perception were analyzed using a combination of GIS spatial statistical analysis from 1224 pieces of environmental sound pressure level data and questionnaire data of human perception collected through soundwalks. The conclusions are as follows: (1) Compared with water bodies, lands perform better in absorbing and reducing the environmental sound pressure level with a decrease of 2.0 dB every 15 m in the terrestrial landscape of rich plant layers and high degree of enclosure, compared to a decrease of 1.5 dB every 15 m in the water landscape with lotus leaves, cruise ships or structures; (2) Sound pressure level and types of sound sources profoundly affect our soundscape perception. Acoustic environment evaluation, soundscape suitability, visual preferences, pleasure perception and relaxation perception are positively correlated with natural sound perception (p < 0.01), while significantly negatively correlated with sound pressure level, human activity and mechanical sound perception. In the end, the correlation between landscape elements and sound pressure level, sound sources and soundscape perception are discussed, and a soundscape optimization strategy for urban parks supported by research data is proposed. Full article

Acoustics has been integrated with archaeology to better understand the social and cultural context of past cultures. Specifically, public events such as rituals or ceremonies, where an appreciation of sound propagation was required to hold an event. Various acoustic techniques have been used to study archaeological sites, providing information about the building characteristics and organizational structures of ancient civilizations. This review aims to present recent advances in Archaeoacoustics worldwide over the last seven years (2016–2022). For this purpose, one hundred and five articles were identified and categorized into two topics: (1) Archaeoacoustics in places, and (2) Archaeoacoustics of musical instruments and pieces. In the first topic, three subtopics were identified: (1) measurement and characterization of places, (2) rock art, and (3) simulation, auralization, and virtualization. Regarding the first subtopic, it was identified that the standards for reverberation times in enclosures are generally applied in their development. In the second subtopic, it was determined that the places selected to make paintings were areas with long reverberation time. The last subtopic, simulation, auralization, and virtualization, is the area of most remarkable growth and innovation. Finally, this review opens the debate to seek standardization of a measurement method that allows comparing results from different investigations. Full article

Turbidity is a commonly used indicator of water quality in continental and marine waters and is mostly caused by suspended and colloidal particles such as organic and inorganic particles. Many methods are available for the measurement of turbidity, ranging from the Secchi disk to infrared light-based benchtop or in situ turbidimeters as well as acoustic methods. The operational methodologies of the large majority of turbidity instruments involve the physics of light scattering and absorption by suspended particles when light is passed through a sample. As such, in the case of in situ monitoring in water bodies, the measurement of turbidity is highly influenced by external light and biofouling. Our motivation for this project is to propose an open-source, low-cost in situ turbidity sensor with a suitable sensitivity and operating range to operate in low-to-medium-turbidity natural waters. This prototype device combines two angular photodetectors and two infrared light sources with different positions, resulting in two different types of light detection, namely nephelometric (i.e., scattering) and attenuation light, according to the ISO 7027 method. The mechanical design involves 3D-printed parts by stereolithography, which are compatible with commercially available waterproof enclosures, thus ensuring easy integration for future users. An effort was made to rely on mostly off-the-shelf electronic components to encourage replication of the system, with the use of a highly integrated photometric front-end commonly used in portable photoplethysmography systems. The sensor was tested in laboratory conditions against a commercial benchtop turbidimeter with Formazin standards. The monitoring results were analyzed, obtaining a linear trendline from 0 to 50 Nephelometric Turbidity Unit (NTU) and an accuracy of +/−0.4 NTU in the 0 to 10 NTU range with a response time of less than 100 ms. Full article

Both the building design and the construction process determine the indoor acoustic quality of enclosures. A suitable indoor acoustic environment is crucial for the productivity and well-being of users. For this purpose, Reverberation Time (RT) is often calculated or measured in situ. Recently, Building Information Modelling (BIM) has provided a new paradigm to face building projects. Nevertheless, little research has been conducted on the optimisation of indoor acoustics using BIM methodology. In this context, the objective of this work is to propose and develop a BIM-based framework for the analysis, evaluation and optimization of the RT. The proposed procedure allows designers to explore alternatives in order to achieve an adequate acoustic performance without any further needs of specific software. This proposal is devised to consider some important characteristics of the project, such as its location, applicable regulations, room uses, materials and costs. This framework calculates the solution set that meets the requirements, showing the set of optimal solutions according to the minimization of both the cost and the optimum absorbent surface area. BFRT contributes by offering a tool to support the decision making process of designers during the initial design phase in the field of acoustic conditioning of buildings. Full article