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Acoustics

Acoustics is an international, peer-reviewed, open access journal on acoustics science and engineering, published quarterly online by MDPI.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within ESCI (Web of Science), Scopus, and other databases.
Journal Rank: CiteScore - Q2 (Acoustics and Ultrasonics)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 22.3 days after submission; acceptance to publication is undertaken in 4.6 days (median values for papers published in this journal in the first half of 2025).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.

Impact Factor: 1.2 (2024); 5-Year Impact Factor: 1.7 (2024)

Imprint Information Journal Flyer Open Access ISSN: 2624-599X

Latest Articles

19 pages, 4389 KB

Open AccessArticle

Noise-Reducing Structure Optimization of Inverted Bucket Steam Valves Based on SVM-NOA

by Shuxun Li, Yiting Wang, Dan Liu, Wei Li, Yuhao Tian and Jianwei Wang

Acoustics 2025, 7(4), 74; https://doi.org/10.3390/acoustics7040074 - 13 Nov 2025

The inverted bucket steam valve is a key piece of equipment in steam systems. Optimizing its noise reduction performance via intelligent algorithms is crucial for enhancing the stability of steam systems. In this study, the nutcracker optimization algorithm (NOA) was investigated and improved. [...] Read more.

The inverted bucket steam valve is a key piece of equipment in steam systems. Optimizing its noise reduction performance via intelligent algorithms is crucial for enhancing the stability of steam systems. In this study, the nutcracker optimization algorithm (NOA) was investigated and improved. A simulation method coupling computational fluid dynamics (CFD) with acoustic software was employed to characterize the acoustic properties of inverted bucket steam valves equipped with noise-reducing elements of different structures. Subsequently, the structural dimensions of the valve’s noise-reducing element were optimized using a support vector machine (SVM)-based surrogate model and the improved NOA. Concurrently, experimental tests were conducted on the inverted bucket steam valve before and after optimization to validate the simulation accuracy. The experimental results demonstrate that the SVM-NOA increases the maximum transmission loss (TL) of the valve’s noise-reducing element by 44.14 dB, with the error between experimental and simulation results being less than 3%. This verifies the accuracy of the acoustic simulation method and confirms the practicality and versatility of the SVM-NOA for solving real-world engineering problems. Full article

(This article belongs to the Special Issue Vibration and Noise (2nd Edition))

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20 pages, 6476 KB

Open AccessArticle

Enhancing the Accuracy of Monopole and Dipole Source Identification with Vision Transformer

by Junwen Chen, Bohan Ma, Cheng Wei Lee, Xun Liu and Wei Ma

Acoustics 2025, 7(4), 73; https://doi.org/10.3390/acoustics7040073 - 10 Nov 2025

The identification of mixed monopole and dipole sound sources under highly randomized acoustic environments is of interest in many industrial applications. The DAMAS–MS method is one of the few methods that has been explicitly developed to address this problem. However, it suffers from [...] Read more.

The identification of mixed monopole and dipole sound sources under highly randomized acoustic environments is of interest in many industrial applications. The DAMAS–MS method is one of the few methods that has been explicitly developed to address this problem. However, it suffers from a critical constraint in that it consistently exhibits limited accuracy in identifying monopole sources, which leads to their underestimation in the final results. To overcome this constraint, this paper proposed a novel identification framework that integrates vision transformer (ViT) with beamforming techniques. The framework leverages preliminary beamforming results to construct input features by extracting the real and imaginary components of the cross-spectral matrix at target frequencies and incorporating spatial position encodings derived from estimated source locations. To ensure adaptability to varying source densities, multiple ViT sub-models are trained on representative scenarios. This strategy enables effective generalization across the target range and supports multi-label identification of monopole and dipole sources with varied configurations. Furthermore, anechoic chamber experiments with synthesized monopole and dipole emitters validate the method’s stability under single-frequency excitation. Compared to the DAMAS–MS method, the proposed method achieves improved identification accuracy for monopole sources, while maintaining comparable performance in dipole source identification, underscoring its potential for practical applications. Full article

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14 pages, 738 KB

Open AccessOpinion

Envisioning the Future of Machine Learning in the Early Detection of Neurodevelopmental and Neurodegenerative Disorders via Speech and Language Biomarkers

by Georgios P. Georgiou

Acoustics 2025, 7(4), 72; https://doi.org/10.3390/acoustics7040072 - 10 Nov 2025

Speech and language offer a rich, non-invasive window into brain health. Advances in machine learning (ML) have enabled increasingly accurate detection of neurodevelopmental and neurodegenerative disorders through these modalities. This paper envisions the future of ML in the early detection of neurodevelopmental disorders [...] Read more.

Speech and language offer a rich, non-invasive window into brain health. Advances in machine learning (ML) have enabled increasingly accurate detection of neurodevelopmental and neurodegenerative disorders through these modalities. This paper envisions the future of ML in the early detection of neurodevelopmental disorders like autism spectrum disorder and attention-deficit/hyperactivity disorder, and neurodegenerative disorders, such as Parkinson’s disease and Alzheimer’s disease, through speech and language biomarkers. We explore the current landscape of ML techniques, including deep learning and multimodal approaches, and review their applications across various conditions, highlighting both successes and inherent limitations. Our core contribution lies in outlining future trends across several critical dimensions. These include the enhancement of data availability and quality, the evolution of models, the development of multilingual and cross-cultural models, the establishment of regulatory and clinical translation frameworks, and the creation of hybrid systems enabling human–artificial intelligence (AI) collaboration. Finally, we conclude with a vision for future directions, emphasizing the potential integration of ML-driven speech diagnostics into public health infrastructure, the development of patient-specific explainable AI, and its synergistic combination with genomics and brain imaging for holistic brain health assessment. Overcoming substantial hurdles in validation, generalization, and clinical adoption, the field is poised to shift toward ubiquitous, accessible, and highly personalized tools for early diagnosis. Full article

(This article belongs to the Special Issue Artificial Intelligence in Acoustic Phonetics)

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19 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 - 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

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

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

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

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

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

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

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

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

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

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

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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16 pages, 9898 KB

Open AccessArticle

Applicability of Traditional Acoustic Technology for Underwater Archeology: A Case Study of Model Detection in Xiamen Bay

by Xudong Fang, Jianglong Zheng, Shengtao Zhou, Zepeng Huang, Boran Liu, Ping Chen and Jiang Xu

Acoustics 2025, 7(3), 59; https://doi.org/10.3390/acoustics7030059 - 22 Sep 2025

This study addresses the applicability of conventional marine acoustic technologies for detecting non-metal artifacts. Based on the typical environment in Xiamen Bay, we evaluated the detection efficacy of common multibeam sonar, side-scan sonar, and sub-bottom profiling sonar through a controlled model experiment system. [...] Read more.

This study addresses the applicability of conventional marine acoustic technologies for detecting non-metal artifacts. Based on the typical environment in Xiamen Bay, we evaluated the detection efficacy of common multibeam sonar, side-scan sonar, and sub-bottom profiling sonar through a controlled model experiment system. We employed ceramic artifact replicas (ranging in size from 10 to 70 cm) and incorporated acoustic parameter optimization to elucidate the applicability boundaries of different technologies. The results indicate that multibeam sonar can identify clustered targets larger than 0.5 m, but is limited in resolving small individual targets (less than 30 cm) due to terrain detail constraints. Side-scan sonar, under low-speed (less than 4 knots) and near-bottom operating conditions, effectively captures the high-intensity echo characteristics of ceramic targets, achieving a maximum effective detection range of more than 40 m. High-frequency sub-bottom profiler (94–110 kHz) offers resolution advantages for exposed artifacts, while low-frequency signals (5–15 kHz) provide theoretical support for detecting subsequently buried targets. Furthermore, the study quantifies the coupling effects of substrate type, target size, and surface roughness on acoustic responses. We propose a synergistic detection workflow comprising “multibeam initial screening—side-scan fine mapping—sub-bottom profiling validation,” which provides empirical support for the optimization and standardization of underwater archeological technologies in complex marine environments. Full article

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31 pages, 6461 KB

Open AccessReview

Advancements in Super-High Frequency Al(Sc)N BAW Resonators for 5G and Beyond

by Chen Li, Ruidong Qin, Wentong Dou, Chongyang Huo, Xuanqi Huang, Zhiqiang Mu, Weimin Li and Wenjie Yu

Acoustics 2025, 7(3), 58; https://doi.org/10.3390/acoustics7030058 - 21 Sep 2025

With the booming development of the 5G market in recent years, super-high frequency (SHF) resonators will play an increasingly critical role in 5G and future communication systems. Facing the growing market demand for miniaturized, high-bandwidth, and low insertion loss filters, the design of [...] Read more.

With the booming development of the 5G market in recent years, super-high frequency (SHF) resonators will play an increasingly critical role in 5G and future communication systems. Facing the growing market demand for miniaturized, high-bandwidth, and low insertion loss filters, the design of SHF resonators and filters with a high effective electromechanical coupling coefficient (K²_eff) and quality factor, low insertion loss, high passband flatness, strong out-of-band rejection, and high power handling capacity has placed high demands on piezoelectric material preparation, process optimization, and resonator design. The polarity-inverted Al(Sc)N multilayer substrate has become one of the key solutions for SHF resonators. This review provides a comprehensive overview of the recent advances in SHF Al(Sc)N bulk acoustic wave (BAW) resonators. It systematically discusses the device design methodologies, structural configurations, and material synthesis techniques for high-quality Al(Sc)N thin films. Particular emphasis is placed on the underlying mechanisms and engineering strategies for polarity control in Al(Sc)N-based periodically poled multilayer structures. The progress in periodically poled piezoelectric film (P3F) BAW resonators is also examined, with special attention to their ability to significantly boost the operating frequency of BAW devices without reducing the thickness of the piezoelectric layer, while maintaining a high K²_eff. Finally, the review outlines current challenges and future directions for achieving a higher quality factor (Q), improved frequency scalability, and greater integration compatibility in SHF acoustic devices, paving the way for next-generation radio frequency (RF) front-end technologies in 5G/6G and beyond. Full article

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13 pages, 1697 KB

Open AccessArticle

A Note on the Sound Absorption Characteristics of Microperforated Panels with Non-Circular Holes

by Kimihiro Sakagami and Sakurako Abe

Acoustics 2025, 7(3), 57; https://doi.org/10.3390/acoustics7030057 - 16 Sep 2025

This study examines the characteristic parameters required for non-circular-hole microperforated panels (MPPs) to achieve sound absorption performance comparable to that of conventional circular-hole MPPs. Through numerical analysis, the flow resistivity and perforation ratio were found to be key parameters influencing the absorption characteristics [...] Read more.

This study examines the characteristic parameters required for non-circular-hole microperforated panels (MPPs) to achieve sound absorption performance comparable to that of conventional circular-hole MPPs. Through numerical analysis, the flow resistivity and perforation ratio were found to be key parameters influencing the absorption characteristics of MPPs with square and equilateral triangular holes. The results indicate that for square-hole MPPs, matching either the flow resistivity alone or both the flow resistivity and perforation ratio to those of circular-hole MPPs leads to similar sound absorption characteristics. In contrast, for equilateral triangular-hole MPPs, both the above parameters must be matched to ensure comparable performance. Furthermore, this study explores MPPs incorporating a combination of circular and non-circular holes. It was confirmed that by appropriately matching the flow resistivity and perforation ratio, such mixed-hole MPPs can achieve sound absorption characteristics similar to those of MPPs composed solely of circular holes. These findings contribute to the broader design possibilities of MPPs, providing a foundation for optimising hole geometries in practical applications where manufacturing constraints or aesthetic considerations may necessitate non-circular hole patterns. Full article

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28 pages, 7369 KB

Open AccessArticle

Comparison of Impulse Response Generation Methods for a Simple Shoebox-Shaped Room

by Lloyd May, Nima Farzaneh, Orchisama Das and Jonathan S. Abel

Acoustics 2025, 7(3), 56; https://doi.org/10.3390/acoustics7030056 - 6 Sep 2025

Cited by 1

Simulated room impulse responses (RIRs) are important tools for studying architectural acoustics. Many methods exist to generate RIRs, each with unique properties that need to be considered when choosing an RIR synthesis technique. Despite the variation in synthesis techniques, there is a dearth [...] Read more.

Simulated room impulse responses (RIRs) are important tools for studying architectural acoustics. Many methods exist to generate RIRs, each with unique properties that need to be considered when choosing an RIR synthesis technique. Despite the variation in synthesis techniques, there is a dearth of comparisons between these techniques. To address this, a comprehensive comparison of four major categories of RIR synthesis techniques was conducted: wave-based methods (hybrid FEM and modal analysis), geometrical acoustics methods (the image source method and ray tracing), delay-network reverberators (SDNs), and statistical methods (Sabine-NED). To compare these techniques, RIRs were recorded in a simple shoebox-shaped racquetball court, and we compared the synthesized RIRs against these recordings. We conducted both objective analyses, such as energy decay curves, normalized echo density, and frequency-dependent decay times, and a perceptual assessment of synthesized RIRs, which consisted of a listening assessment with 29 participants that utilized a MUSHRA comparison methodology. Our results reveal distinct advantages and limitations across synthesis categories. For example, the Sabine-NED technique was indistinguishable from the recorded IR, but it does not scale well with increasing geometric complexity. These findings provide valuable insights for selecting appropriate synthesis techniques for applications in architectural acoustics, immersive audio rendering, and virtual reality environments. Full article

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B-Scan Imaging and 3D Visualization of Hardened Layer Depth Profile in Linear Guide Rails Based on Ultrasonic Shear Wave Backscattering Technique

by Peiqiang Chen, Lingtong Chen, Mingyang Xue and Chenlong Yang

Acoustics 2025, 7(3), 55; https://doi.org/10.3390/acoustics7030055 - 31 Aug 2025

In order to measure the depth profile of the heat-treated case-hardened layer of linear guides, this paper proposes a B-scan imaging and 3D visualization method for detecting the depth profile of the case-hardened layer of linear guides based on the ultrasonic transverse wave [...] Read more.

In order to measure the depth profile of the heat-treated case-hardened layer of linear guides, this paper proposes a B-scan imaging and 3D visualization method for detecting the depth profile of the case-hardened layer of linear guides based on the ultrasonic transverse wave backscattering technology. Firstly, by analyzing the generation mechanism of ultrasonic transverse waves and their advantages in material detection, and combining the differences in metallographic structure and hardness properties between the case-hardened layer and the base material, an ultrasonic transverse wave backscattering model for the case-hardened layer of linear guides was established. Then, an ultrasonic transverse wave detection experiment for the GH20 linear guide was designed and carried out to obtain the A-scan signals of the case-hardened layer depth at different positions on the cross-section of the linear guide. Finally, the A-scan signals obtained from the detection were used to generate the B-scan image of the case-hardened layer depth profile, and the 3D visualization of the case-hardened layer of the linear guide was achieved using Python and VTK tools. The experimental results show that the error between the measurement results of ultrasonic transverse waves and those of the metallographic method is 0.063 mm, and the detection results are within the allowable error range. This research provides an efficient, intuitive, and reliable technical method for detecting the depth of the case-hardened layer of linear guides in the industrial field. Full article

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