Acoustics

20 pages, 1290 KB

Open AccessReview

Dependencies of Underwater Noise from Offshore Wind Farms on Distance, Wind Speed, and Turbine Power

by Qitong Ge, Haoran Yao, Sihao Qian, Xuguang Zhang and Hongyi Guo

Acoustics 2025, 7(4), 71; https://doi.org/10.3390/acoustics7040071 (registering DOI) - 4 Nov 2025

The operational phase of offshore wind farms, lasting up to 20–25 years, exceeds the construction phase in duration. The ecological effects of underwater noise demand serious consideration, necessitating urgent research into its acoustic characteristics. This review conducts a systematic analysis of measurements of [...] Read more.

The operational phase of offshore wind farms, lasting up to 20–25 years, exceeds the construction phase in duration. The ecological effects of underwater noise demand serious consideration, necessitating urgent research into its acoustic characteristics. This review conducts a systematic analysis of measurements of underwater noise from operational offshore wind farms, considering the correlations between turbine noise and distance, wind speed, turbine power, and foundation type. Propagation distance is the most critical factor influencing the underwater sound pressure level (SPL) of wind turbines, exhibiting a negative correlation with the SPL, with an attenuation of approximately 20.4 dB/decade. In contrast, wind speed and turbine power show a positive correlation with the SPL, with increase rates of 18.5 dB/decade and 12.4 dB/decade, respectively. Further analysis shows that foundation type and drive technology also have a significant impact on underwater SPL. With technological innovation, specifically the upgrade from conventional geared drive to direct-drive technology, the level of underwater noise can be reduced by approximately 9 dB, with the primary peak frequency being shifted to a lower range. Moreover, significant variations in SPLs were noted with the utilization of various types of foundation structures, with monopile foundations exhibiting the highest SPLs of underwater noise. These conclusions have important reference value for the scientific assessment of the health of aquatic organisms and ecosystems. Full article

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17 pages, 2246 KB

Open AccessArticle

Spatial Sound Modeling and Optimization of Flight Simulator with Multiple Off-Center Listening Positions

by Yang Yang, Shuling Dai, Xiaoyong Lei and Yu Jia

Acoustics 2025, 7(4), 70; https://doi.org/10.3390/acoustics7040070 - 31 Oct 2025

Viewed by 106

Abstract

Accurate spatial sound localization is critical in flight simulators for enhancing situational awareness and pilot training effectiveness, particularly for diagnosing severe faults like engine surge which emit directional sound cues. However, existing spatial audio systems are primarily optimized for a single central listening [...] Read more.

Accurate spatial sound localization is critical in flight simulators for enhancing situational awareness and pilot training effectiveness, particularly for diagnosing severe faults like engine surge which emit directional sound cues. However, existing spatial audio systems are primarily optimized for a single central listening position, failing to provide consistent localization accuracy for pilots seated in naturally off-center positions within the cockpit. To bridge this gap, this paper proposes a novel compensation method incorporating near-field loudspeakers. A comprehensive mathematical model for multiple off-center listening points is established based on acoustic velocity and energy vector theory. We further formulate a dual-phase optimization framework: a multi-objective model employing the NSGA-II algorithm to Pareto-optimize the trade-off between minimizing localization error and maximizing spatial stability, followed by a maximin model that guarantees robustness during head movements. A formal listening experiment demonstrates that the proposed optimized design significantly improves both localization accuracy and stability over conventional uniform layouts, thereby enhancing the fidelity and safety of flight simulation training. Full article

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21 pages, 4212 KB

Open AccessArticle

A Low-Cost Detection Method for Acoustic Defects in Building Components: Compressed Nearfield Acoustic Holography

by Chenxi Yang, Hongwei Wang, Qiaochu Wang and Shujie Li

Acoustics 2025, 7(4), 69; https://doi.org/10.3390/acoustics7040069 - 30 Oct 2025

Viewed by 129

Abstract

The accurate diagnosis of acoustic defects and the precise assessment of the performance of building components are highly dependent on massive amounts of sampling data. In this study, we try to combine the compressed sensing theory with the nearfield acoustic holographic sound insulation [...] Read more.

The accurate diagnosis of acoustic defects and the precise assessment of the performance of building components are highly dependent on massive amounts of sampling data. In this study, we try to combine the compressed sensing theory with the nearfield acoustic holographic sound insulation measurement method and introduce a noise reduction algorithm so as to realize the sound pressure distribution accuracy similar to that of the conventional sampling under low-density data conditions. Numerical simulation results show that the reconstruction error of the method proposed in this paper is only 8.21% higher than that of the complete sampling under the condition of 20% sampling rate, and the reconstruction error is only 2.50% higher than that of the complete sampling under the condition of 40% sampling rate. The reconstruction error under 50% sampling rate and 6.65 dB SNR is only 4.81% higher than the complete sampling, which is basically consistent with the numerical simulation; the sound insulation is only 1 dB lower than that measured by the sound pressure method, and the acoustic defects of the components can basically be identified. The results of this study have a positive significance in simplifying the process of sound insulation measurement in most scenarios. Full article

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36 pages, 2468 KB

Open AccessSystematic Review

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

by Özlem Gök Tokgöz, Margret Sibylle Engel, Cherif Othmani and M. Ercan Altinsoy

Acoustics 2025, 7(4), 68; https://doi.org/10.3390/acoustics7040068 - 17 Oct 2025

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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 [...] Read more.

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. Full article

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27 pages, 3329 KB

Open AccessArticle

A Model for the Dynamics of Stable Gas Bubbles in Viscoelastic Fluids Based on Bubble Volume Variation

by Elena V. Carreras-Casanova and Christian Vanhille

Acoustics 2025, 7(4), 67; https://doi.org/10.3390/acoustics7040067 - 16 Oct 2025

Viewed by 358

Abstract

We present a novel formulation of the Rayleigh–Plesset equation to describe stable gas bubble dynamics in viscoelastic media, using bubble volume variation, rather than radius, as the primary variable of the resulting nonlinear ordinary differential equation. This formulation incorporates the linear Kelvin–Voigt model [...] Read more.

We present a novel formulation of the Rayleigh–Plesset equation to describe stable gas bubble dynamics in viscoelastic media, using bubble volume variation, rather than radius, as the primary variable of the resulting nonlinear ordinary differential equation. This formulation incorporates the linear Kelvin–Voigt model as the constitutive relation for the surrounding fluid, capturing both viscous and elastic contributions, to track the oscillations of a gas bubble subjected to an ultrasonic field over time. The proposed model is solved numerically, subjected to a convergence analysis, and validated by comparisons with theoretical and experimental results from the literature. We systematically investigate the nonlinear oscillations of a single spherical gas bubble in various viscoelastic environments, each modeled with varying levels of rheological complexity. The influence of medium properties, specifically shear elasticity and viscosity, is examined in detail across both linear and nonlinear regimes. This work improves our understanding of stable cavitation dynamics by emphasizing key differences from Newtonian fluid behavior, resonance frequency, phase shifts, and oscillation damping. Elasticity has a pronounced effect in low-viscosity media, whereas viscosity emerges as the dominant factor modulating the amplitude of oscillations in both the linear and nonlinear regimes. The model equation developed here provides a robust tool for analyzing how viscoelastic properties affect bubble dynamics, contributing to improved the prediction and control of stable cavitation phenomena in complex media. Full article

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20 pages, 15206 KB

Open AccessProject Report

Vaulted Harmonies: Archaeoacoustic Concert in Notre-Dame de Paris

by David Poirier-Quinot, Jean-Marc Lyzwa, Jérôme Mouscadet and Brian F. G. Katz

Acoustics 2025, 7(4), 66; https://doi.org/10.3390/acoustics7040066 - 15 Oct 2025

Viewed by 513

Abstract

This paper presents Vaulted Harmonies, a 66-min animated feature film created as part of the scientific outreach effort of the Past Has Ears at Notre-Dame project (ANR-PHEND). The project investigates the historical acoustics of Notre-Dame de Paris and their influence on music over [...] Read more.

This paper presents Vaulted Harmonies, a 66-min animated feature film created as part of the scientific outreach effort of the Past Has Ears at Notre-Dame project (ANR-PHEND). The project investigates the historical acoustics of Notre-Dame de Paris and their influence on music over the centuries. The film is structured around eleven musical pieces spanning the 12th to 20th centuries, each chosen for its relevance to the cathedral’s history and musical heritage. Details include how each piece was recorded and auralised using a calibrated geometric acoustic model that reflects the acoustics of the corresponding historical period. Further details describe the creation of the CGI renderings of Notre-Dame, which feature animated musicians synchronised with the music they perform, enhancing the immersive quality of the experience. These musical performances are interwoven with short documentary-style segments that provide historical and musicological context. The film adopts a first-person perspective in which the acoustics and visuals dynamically follow the camera’s movement, offering a virtual reality-like experience in a cinematic format. Vaulted Harmonies thus functions both as an engaging archaeoacoustic outreach project and as a standalone virtual concert rooted in historically informed performance and production. Full article

(This article belongs to the Special Issue The Past Has Ears: Archaeoacoustics and Acoustic Heritage)

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11 pages, 9295 KB

Open AccessArticle

Berlage Oscillator as a Mathematical Model of High-Frequency Geoacoustic Emission with One Dislocation Source

by Darya Sergienko and Roman Parovik

Acoustics 2025, 7(4), 65; https://doi.org/10.3390/acoustics7040065 - 14 Oct 2025

Viewed by 260

Abstract

A mathematical model of high-frequency geoacoustic emission for a single dislocation radiation source is suggested in the papper. The mathematical model is a linear Berlage oscillator with non-constant coefficients whose solution is the Berlage function momentum. Further, the values of the parameters of [...] Read more.

A mathematical model of high-frequency geoacoustic emission for a single dislocation radiation source is suggested in the papper. The mathematical model is a linear Berlage oscillator with non-constant coefficients whose solution is the Berlage function momentum. Further, the values of the parameters of the Berlage pulse are specified using experimental data. For this purpose, the problem of multidimensional optimization is solved, which consists of two stages: global optimization using the differential evolution method and local optimization according to the Nelder-Mead method. Statistics are given to confirm the correctness of the obtained results: standard error and coefficient of determination. It is shown that two-stage multivariate optimization makes it possible to refine the parameters of the Berlage pulse with a sufficiently high accuracy to describe high-frequency geoacoustic emission. Full article

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37 pages, 9023 KB

Open AccessArticle

The Impact of Soundscape on Pedestrian Comfort, Perception and Walking Experience in Béjaïa, Algeria

by Yacine Mansouri, Mohamed Elhadi Matallah, Abdelghani Attar, Waqas Ahmed Mahar and Shady Attia

Acoustics 2025, 7(4), 64; https://doi.org/10.3390/acoustics7040064 - 13 Oct 2025

Viewed by 493

Abstract

This study explores the influence of the urban soundscape on pedestrian perception and walking experience in the historic and lower parts of Béjaïa, Algeria. More precisely, the analysis investigates how variations in soundscape configuration relate to perceived comfort, safety, and walking pleasantness across [...] Read more.

This study explores the influence of the urban soundscape on pedestrian perception and walking experience in the historic and lower parts of Béjaïa, Algeria. More precisely, the analysis investigates how variations in soundscape configuration relate to perceived comfort, safety, and walking pleasantness across five morphologically distinct urban zones. A mixed-method approach combining quantitative tools (LAeq acoustic measurements) and qualitative methods (soundwalks, sound diaries, and mental maps) was applied in accordance with ISO 12913. The study involved 50 participants for the sound diaries and 58 for the soundwalks. Results show that natural and social sounds enhance perceived comfort and safety, while mechanical noise is associated with discomfort and avoidance behaviors. In the morning, moderate to strong correlations were observed between sound comfort and visual perception (ρ = 0.58, p = 0.001, 95% CI [0.27; 0.80]), as well as between sound comfort and walking pleasantness (ρ = 0.40, p = 0.033, 95% CI [0.05; 0.67]). The study highlights the need to integrate soundscape considerations into urban planning and heritage conservation strategies. Full article

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22 pages, 5131 KB

Open AccessArticle

Predictive Torque Control for Induction Machine Fed by Voltage Source Inverter: Theoretical and Experimental Analysis on Acoustic Noise

by Bouyahi Henda and Adel Khedher

Acoustics 2025, 7(4), 63; https://doi.org/10.3390/acoustics7040063 - 11 Oct 2025

Viewed by 287

Abstract

Induction motors piloted by voltage source inverters constitute a major source of acoustic noise in industry. The discrete tonal bands generated by induction motor stator current spectra controlled by the fixed Pulse Width Modulation (PWM) technique have damaging effects on the electronic noise [...] Read more.

Induction motors piloted by voltage source inverters constitute a major source of acoustic noise in industry. The discrete tonal bands generated by induction motor stator current spectra controlled by the fixed Pulse Width Modulation (PWM) technique have damaging effects on the electronic noise source. Nowadays, the investigation of new advanced control techniques for variable speed drives has developed a potential investigation field. Finite state model predictive control has recently become a very popular research focus for power electronic converter control. The flexibility of this control shows that the switching times are generated using all the information on the drive status. Predictive Torque Control (PTC), space vector PWM and random PWM are investigated in this paper in terms of acoustic noise emitted by an induction machine fed by a three-phase two-level inverter. A comparative study based on electrical and mechanical magnitudes, as well as harmonic analysis of the stator current, is presented and discussed. An experimental test bench is also developed to examine the effect of the proposed PTC and PWM techniques on the acoustic noise of an induction motor fed by a three-phase two-level voltage source converter. Full article

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16 pages, 2506 KB

Open AccessArticle

Fitting Methods for Empirical Models of Open-Pore Foams

by Jesús Alba, Romina del Rey and Juan C. Rodríguez

Acoustics 2025, 7(4), 62; https://doi.org/10.3390/acoustics7040062 - 30 Sep 2025

Viewed by 859

Abstract

Sound-absorbing materials in the frequency range can be characterised upon the basis of their propagation constant and characteristic impedance. For a number of years, there have been empirical models, such as that of Delany and Bazley, which adjust these parameters to the flow [...] Read more.

Sound-absorbing materials in the frequency range can be characterised upon the basis of their propagation constant and characteristic impedance. For a number of years, there have been empirical models, such as that of Delany and Bazley, which adjust these parameters to the flow resistivity and frequency, defining fitting coefficients. Based on the Delany–Bazley model, further adjustments of these coefficients have been proposed to improve the prediction of specific materials. The most commonly used adjustments are based on a quadratic error function for the normal incidence sound absorption coefficient or the surface impedance. Three adjustment methods are displayed in this paper to obtain new open-pore foam coefficients. The propagation constant and characteristic impedance measurements are adjusted, with different error functions and minimisation algorithms. New and improved models are obtained upon the basis of these three methods. The results obtained display satisfactory adjustments of all the material variables. Full article

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17 pages, 2322 KB

Open AccessArticle

Bifurcation in Stick–Slip-Induced Low-Frequency Brake Noises: Experimental and Numerical Study

by Deborah Audretsch, Daniel Wallner, Michael Frey and Frank Gauterin

Acoustics 2025, 7(4), 61; https://doi.org/10.3390/acoustics7040061 - 26 Sep 2025

Viewed by 513

Abstract

The term honk noise describes a low-frequency brake noise from approximately 400 Hz to 500 Hz which arises at extremely low speeds and low brake pressures. Manoeuvres like slowly releasing the brake at a hill or gently braking against the drag torque of [...] Read more.

The term honk noise describes a low-frequency brake noise from approximately 400 Hz to 500 Hz which arises at extremely low speeds and low brake pressures. Manoeuvres like slowly releasing the brake at a hill or gently braking against the drag torque of an automatic gearbox lead to honk noise. Under the same conditions, we observed creep groan at about 80 Hz. It has been shown that honk noise usually occurs after or alternates with creep groan. For this reason, it is assumed that honk noise—like creep groan—is a stick–slip-induced phenomenon and therefore shows highly nonlinear behaviour. In this paper, we present an approach for explaining the onset of honk noise under stick–slip excitation. A minimal model consisting of coupled mass oscillators excited by stick–slip is investigated. The model was able to reproduce the phenomena observed in the experiments. Thus, it is suitable for explaining the mechanisms leading to honk and estimate the influence of basic parameter variations. The lessons learned are a crucial step towards more realistic finite element or multi-body simulation methods, which have high potential for saving costs in the noise, vibration, and harshness (NVH) development process of brake systems. Full article

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22 pages, 3966 KB

Open AccessArticle

Broadband Acoustic Modal Identification by Combined Sensor Array Measurements

by Kunbo Xu, Dongjun Liu, Zekai Zong, Chenzhe Xiang, Weiyang Qiao and Liang Yu

Acoustics 2025, 7(4), 60; https://doi.org/10.3390/acoustics7040060 - 23 Sep 2025

Viewed by 411

Abstract

This paper proposes a synchronous measurement method for broadband acoustic modal identification based on a combined microphone array, which is capable of overcoming the acoustic modal aliasing issue arising from a limited number of microphones. In the proposed method, the cross-correlation combination of [...] Read more.

This paper proposes a synchronous measurement method for broadband acoustic modal identification based on a combined microphone array, which is capable of overcoming the acoustic modal aliasing issue arising from a limited number of microphones. In the proposed method, the cross-correlation combination of axial and circumferential arrays is performed by utilizing the relevant characteristics of turbulent noise modes, thereby realizing modal identification of turbulent noise in a wide range with a small number of acoustic measurement points. For fast iteration, the modal cross terms are optimized by leveraging the relevant characteristics of turbulent noise modes. This method can effectively distinguish the distribution information of forward- and backward-propagating acoustic modes. The accuracy of the identified acoustic modes is verified through numerical simulations, and the method is experimentally validated using experimental results from an axial flow compressor. The results show that this method can effectively suppress the aliasing problem. Compared with the traditional rotating axial array method, it has higher testing efficiency in circumferential and radial modal identification, requires fewer sound-pressure measurement points, and is more suitable for rapid evaluation of noise reduction designs. Full article

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Acoustics, Volume 7, Issue 4 (December 2025) – 12 articles

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