Archives of Acoustics is an English-language peer-reviewed online quarterly journal publishing original research papers from all areas of acoustics and abstracts from some specialized acoustical conferences. It gives free internet access to its full content to current issues. Archives of Acoustics, the peer-reviewed online quarterly journal, publishes original research papers from areas of acoustics like: linear and nonlinear acoustics: theory, acoustical measurements, and instrumentation acoustics of music: music theory, signal processing, and instrument building physiological acoustics: hearing, audiology, and psychoacoustics speech processing and communication systems: speech production and perception, voice recognition and control architectural, building, and environmental acoustics and soundscape computational and numerical acoustics sound and ultrasound in biology and medicine: ultrasonic imaging, ultrasonography, high-intensity ultrasound, therapeutic ultrasound electroacoustics: research in the field of microphones, loudspeakers, headphones, accelerometers, acoustic calibrators noise, noise control, and vibration: theory and instrumentation for noise determination and sound quality criteria, audio signal processing and transducers, acoustic materials sonochemistry: acoustic cavitation, sonoprocessing, and all aspects of physical and chemical effects of sound ultrasound and ultrasonic transducers underwater acoustics: acoustical oceanography and fisheries acoustics acousto-optics artificial intelligence in acoustic research This journal provides immediate open access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge. All articles are published on Creative Commons licence CC BY 4.0. Archives of Acoustics is available in Diamond Open Access and no fees are charged to the authors or readers. Journal Metrics MNiSW (2024): 100 | Impact Factor 2024: 0.9 (2023: 0.6) | CiteScore 2024: 1.6 (2023: 1.8) | SJR 2024: 0.233 (2023: 0.239) | SNIP 2024: 0.597 (2023: 0.570)
Institute of Fundamental Technological Research (IPPT) of the Polish Academy of Sciences
Copyright on any open access article in the Archives of Acoustics published by the Polish Academy of Sciences and the Institute of Fundamental Technological Research Polish Academy of Sciences is retained by the author(s). The authors grant the Polish Academy of Sciences and the Institute of Fundamental Technological Research Polish Academy of Sciences a license to publish the article and identify themselves as the original publisher. The authors also grant any user the right to use the article freely as long as its integrity is maintained and its original authors, citation details, and publisher are identified. The Creative Commons Attribution 4.0 International CC BY 4.0 formalizes these and other terms and conditions of publishing articles. Exceptions to copyright policy For the articles that were published between 2019– 2023 (including No. 1 and 2, 2023), the policies are as follows: The Creative Commons Attribution License-ShareAlike 4.0 formalizes these and other terms and conditions of publishing articles: https://creativecommons.org/licenses/by-sa/4.0/. For the articles which were previously published, before year 2019, policies that are different from the above. In all such, access to these articles is free from fees or any other access restrictions. Permissions for the use of the texts published in that journal may be sought directly from the Editorial Office of Archives of Acoustics
Optimized Hydrophone Array Empowering Deep Learning–Based Phase Error Correction in Synthetic Aperture Sonar
This study addresses motion robust synthetic aperture sonar by coupling deep learning-based phase error estimation with hydrophone array optimization under 6 degrees of freedom. The objective is to deliver low sidelobe and high-fidelity imagery when surge, sway, heave, roll, pitch, and yaw inject residual phase errors that conventional autofocus and inertial aiding do not fully remove. The method is physics informed and trains an optimized array to predict residual phase from profile stacks and small image patches using a composite loss that blends image consistency, smooth proxies for peak and integrated sidelobe ratios, and phase smoothness. Array geometry is expressed in closed form and is co tuned in the loop with the corrector so that motion sensitivity is reduced before phase correction. Four hydrophone arrays are examined, namely a planar dual spiral, two helices on a cylinder, a hemispherical Fibonacci layout, and an optimized oblate hemisphere with equatorial densification and a mild tilt. Evaluation spans 24 scenarios across 6 motion axes over a 16 targets grid with PSLR, ISLR, PSNR, and RMSE as metrics. Three dimensional and nearly isotropic layouts consistently outperform planar and cylindrical baselines after correction. The optimized array ranks first overall, typically reaching side-lobe floors near −26 to −27 dB with PSNR near 49 to 50 dB and RMSE near 0.0033 and shows aggregated gains over the planar baseline of about −8 dB in sidelobe metrics and about +12 dB in PSNR, while retaining smaller but measurable advantages over the hemi-spherical Fibonacci design. The contribution unifies physics informed deep correction with interpretable array design that advances motion robust SAS image quality and offers actionable guidance for future hydrophone arrays.
Copyright (c) 2026 Hamid Hajirahimi Kashani, Seyed Alireza Seyedin https://creativecommons.org/licenses/by/4.0
The mechanism of formation of the cutoff frequency in an acousto-optic delay line and some proposals for its measurement
The structure of the acousto-optic delay line and possible areas of its application are discussed. The necessity of determining the cutoff frequency of the acousto-optic delay line in all areas of its application is substantiated. The relationship between the cutoff frequency of an electric circuit and its time constant is discussed. The obtained result is extrapolated to the acousto-optic delay line, in which the cutoff frequency is formed by a completely different mechanism. The mechanism of cutoff frequency formation in the acousto-optic delay line is discussed. It is shown that the cutoff frequency in the acousto-optic delay line is formed due to the finite velocity of interaction of the acoustic wave with the light beam in the photoelastic medium. Two methods for measuring the cutoff frequency of the acousto-optic delay line are discussed: the method of system-parametric measurement and the method of cursor measurement. The system-parametric method for measuring the cutoff frequency of the acousto-optic delay line is implemented based on the known values of the laser beam diameter and the velocity of propagation of the acoustic wave in the photoelastic medium. The cursor method for measuring the cutoff frequency of the acousto-optic delay line is implemented based on the parameters of the oscillogram of its response to the input action in the form of a rectangular pulse. Theoretical and experimental aspects of the application of these methods are discussed. Corresponding numerical examples and experimental results are given.
Copyright (c) 2026 Afig Hasanov, Ruslan Hasanov, Elgun Aghayev, Rovshan Ahmadov https://creativecommons.org/licenses/by/4.0
A Study of Damage Modes Recognition of Polypropylene Fiber Reinforced Recycled Aggregate Concrete Based on Principal Components of Acoustic Emission Signals
To investigate the principal components of acoustic emission (AE) signals and damage modes of polypropylene fiber (PPF) reinforced recycled concrete, ten groups of specimens with coarse aggregate (CA) replacement rates of 0% and 25% and different particle sizes were designed and fabricated. Uniaxial compression AE tests were conducted to obtain the AE parameters during the fracture process of PPF reinforced recycled concrete. In this study, the Pearson correlation coefficient was employed to investigate the correlations among AE parameters. Then, the principal component analysis (PCA) was performed on the AE signals to conduct dimensionality reduction of the multi-dimensional data. On this basis, the optimal number of clusters for the principal components of AE signals was determined based on the silhouette coefficient. Finally, the K-means clustering algorithm was introduced to perform cluster analysis on the principal components of AE signals of PPF reinforced recycled concrete. The clustering results were compared with each other to explore the characteristics of each cluster and identify the corresponding damage mode for each cluster. The discriminability of AE parameters with respect to damage modes was investigated, and the research findings can provide a reference for predicting the fracture mechanism of PPF reinforced recycled concrete.
polypropylene fiber reinforced recycled concrete
Copyright (c) 2026 Qianxu Chen, Xin Yang https://creativecommons.org/licenses/by/4.0
Examination of low-frequency sound decay in two connected enclosed spaces having different sound absorption on boundary surfaces
In this paper, a sound decay in two connected enclosed spaces was investigated. The research concerned the low-frequency range, because in this situation the sound decay is predominantly non-exponential. Numerical simulations were performed for a system of two connected rectangular subrooms. The larger subroom was highly reverberant, while the smaller subroom had walls that provided moderate sound damping. Simulation results showed that after switching off the harmonic source, a non-exponential behavior of sound decay is usually observed. This is because many eigenmodes are involved in the sound decay, hence this process strongly depends on both the source frequency and its position. Reverberant properties of the system were also determined using energy decay curves calculated by the reverse-time integration of squared room impulse response. Simulations showed that the effect of the significant difference in sound absorption in subrooms is a wide range of modal reverberation time values, i.e. it is large for eigenmodes localized in a highly reverberant room and small for eigenmodes localized in a damped room. The analyzed room system is therefore characterized by an interesting feature resulting from the localization of eigenmodes. When the source is located in the larger subroom, slowly decaying modes localized in this subroom dominate the sound decay process. However, when the source is located in the smaller subroom, the sound decay in the larger subroom is much faster since non-localized modes with a shorter modal reverberation time are excited within this subroom.
Copyright (c) 2026 Mirosław Meissner https://creativecommons.org/licenses/by/4.0
From Speech to Underwater Acoustics: A Transfer Learning Framework for Real-Time Passive Diver Detection Using Keyword Spotting Models
Passive acoustic detection of divers faces challenges such as low signal-to-noise ratios (SNRs), data scarcity, and latency in conventional methods. This paper proposes Keyword Spotting for Diver Detection (KWS-DD)—a transfer learning framework that repurposes speech-oriented KWS models for data-efficient diver detection. Diver inhalation signatures are treated as acoustic "keywords," enabling adaptation of the transformer-based HuBERT architecture (pre-trained on speech) to identify quasi-periodic respiratory events in underwater audio. The core innovation of this work lies in adapting the state-of-the-art speech model HuBERT for accurate diver detection via non-speech inhalation acoustics. This approach eliminates the need for respiratory cycles accumulation, enabling real-time detection using minimal domain-specific data (120 inhalation samples). Deployed in diverse marine conditions, the solution achieved 94.4% accuracy and 94.6% F1-score for inhalation sounds. This represents a more than 50% range extension over conventional methods, which proved unreliable beyond 10 meters in low-SNR environments. The framework reduces false alarms caused by boat noise and generalizes to external datasets, validating cross-domain transferability. This work bridges AI-based speech processing and passive sonar signal processing, offering a resource-efficient solution for real-time underwater surveillance.
Copyright (c) 2026 Osama Deeb, Saier Mahmoud, Louay Saleh, Assef Jafar, Oumayma Al Dakkak, Ibrahim Chouaib https://creativecommons.org/licenses/by/4.0
Modeling of High-Speed Ultrasonic Testing of Railway Rails in Track Inspection
In the paper the theoretical modeling of ultrasonic testing of railway rails with high scanning speed is considered. The model for the calculation of the ultrasonic field generated by the ultrasonic transducers and the pulse echo amplitude received after wave reflection at the defect is developed. The model is based on well-established principles of elastodynamic theory: the Rayleigh–Sommerfeld integral, the Auld reciprocity relation, and the Kirchhoff approximation. It forms the basis for design of computer program to simulate ultrasonic inspections of railway rails with automated mobile systems. The major innovation introduced in the model is taking into account the high scanning speed of the ultrasonic probes over the rail head and the limited repetition rate of the ultrasonic system. The mentioned aspects of the high-speed rail testing require the revision of one of the basic paradigms of the current ultrasonic models, which assume that the scanning speed of the ultrasonic probe is negligible in comparison to the speed of ultrasonic waves propagating in the tested material. Actually, when scanning rails at a speed of 120 km/h, the ultrasonic probe can change its position up to 5 mm between transmitting and receiving ultrasonic pulses reflected from defects located in the rail foot. Such a shift in the probe position is not negligible and should be considered in calculations. As a consequence, the ultrasonic system’s slow repetition rate and fast scanning speed can make it less likely that certain rail flaws will be found. To quantitatively examine the severity of these phenomena, the new ultrasonic model and related simulation software was developed.
Copyright (c) 2026 Sławomir Mackiewicz, Zbigniew Ranachowski, Tomasz Katz, Tomasz Dębowski, Grzegorz Starzyński https://creativecommons.org/licenses/by/4.0
Musical Key Detection Using a Triple Composite Signature of Fifths
The article introduces a novel algorithm for key detection in musical compositions represented in symbolic form, such as MIDI. The method is based on the analysis of the triple composite signature of fifths, which is formed by combining the signatures of fifths obtained individually for the beginning, end, and entirety of the analyzed piece. The key is determined by the sign of the angle between the characteristic vector of the triple composite signature of fifths and the major/minor mode axis derived from that signature. To evaluate the algorithm’s effectiveness, experiments were conducted using Chopin’s Preludes, Op. 28, pieces from the Saarland Music Data: MIDI-Audio Piano Music, as well as pieces from the Schubert Winterreise Dataset. As a reference method, a correlation-based algorithm implementing various tonal profiles was used. The proposed algorithm achieved the highest accuracy for Chopin’s Preludes and the Schubert Winterreise Dataset (91.67% in both cases), while for the Saarland Music Data, its accuracy was lower than that of the correlational approaches (72.34%). The main advantages of the presented algorithm are low computational complexity, stable decision-making when extending the analytical window, as well as incorporation of expert analysis aspects, particularly by focusing on the beginning and end of the composition.
Copyright (c) 2026 Tomasz Łukaszewicz, Dariusz Kania https://creativecommons.org/licenses/by/4.0
Broadband Vibration-Isolating Metamaterial for MRI-Induced Vibrations
The magnetic resonance imaging (MRI) is an important diagnostic tool in medical field. The vibrations originated from the gradient coil of MRI system leads to loud operational noise. The study explores the numerical investigation of elastic metamaterial for attenuation of MRI induced vibrations that could radiate as sound at air-structure interface. The elastic metamaterials with embedded resonators can significantly attenuate the wave propagation by opening a local resonance bandgap. In this study the wave propagation properties of two models of elastic metamaterial are analysed. The dispersion diagrams are studied with parametric analysis investigating the influence of the different geometric features on the bandgap generation. The model the metamaterial was analysed with finite element analysis to investigate the wave attenuation performance. The frequency analysis of the multicellular model showed high transmission loss corresponding to the bandgaps in calculated dispersion diagrams. The results revealed that, the optimum model of the metamaterial showed overlap of 72.3 % with the vibration frequency range of the MRI scanner and the frequency analysis of the multicellular arrangement reported transmission loss up to 115.7 dB. These results demonstrate the potential of the such elastic metamaterial for targeted vibro-acoustic control and provide a framework for design of structures for wave attenuation in sensitive acoustic environments.
Copyright (c) 2026 Swapnil Arawade, Janusz Piotr Piechowicz https://creativecommons.org/licenses/by/4.0
Indian Sign Language Alphabet Recognition and Speech Synthesis Using a Hybrid Deep Learning Approach
Indian Sign Language (ISL) is vital for communication among India's hearing-impaired community. However, the lack of standardised datasets and reliable identification frameworks has hampered the use of ISL in modern assistive technology. This paper presents a deep learning-based solution to robust ISL alphabet identification, with an emphasis on both accuracy and practical use. A curated static ISL alphabet collection was created by combining authoritative visual references from the official Indian Sign Language website and the Ramakrishna Mission Vivekananda Educational and Research Institute (RKMVERI). Multiple deep learning models were trained and assessed, including CNN, ResNet-50, DenseNet-121, VGG16, MobileNetV2, and EfficientNet-B0, with a new hybrid CNN-ResNet architecture outperforming the others. 98% classification accuracy is achieved by the suggested approach, outperforming individual baseline models. Furthermore, the framework is expanded to support real-time applications, combining webcam-based capture with immediate conversion of recognized signs to textual and synthesized vocal output. Comprehensive performance evaluation, including confusion matrix analysis and ROC curves, demonstrates the solution's durability and practical applicability. This research enhances accessibility, promotes inclusive education, and prepares the path for scalable sign language translation systems in real-world human-machine interaction scenarios by enabling accurate and real-time ISL recognition with voice feedback.
Copyright (c) 2025 Aswani Sivan, Chandra Eswaran https://creativecommons.org/licenses/by/4.0
Construction Method of Sparse Dictionary for Multi-Order FRFT Domain Feature Fusion
Reverberation constitutes a primary source of interference for active sonar signals, particularly the intense reverberation originating from reflections of the incident signal. Sharing the same generation mechanism as the target echo, it severely hampers the extraction and analysis of the target signal. To enhance signal processing capabilities under strong reverberation, this paper proposes a sparse dictionary construction method based on multi-order fractional Fourier transform (FRFT) domain feature fusion. This method exploits the distinctive characteristics exhibited by target echoes and strong reverberation signals across different fractional transform domains to discriminate between them. It constructs sparse sub-dictionaries using these distinct fractional orders, trains the weights of each sub-dictionary via an adaptive gradient optimization strategy to achieve sparse representation of the signal, suppresses strong interference in the sparse domain, and reconstructs the target signal through a reconstruction process, thereby achieving the goal of extracting the target signal while suppressing strong interference. Results from processing lake trial data demonstrate that the proposed method can effectively extract target echo signals amidst strong reverberation, with the signal-to-reverberation ratio improvement consistently no less than 2.1 dB and reaching up to 15.6 dB. This method provides an effective approach for the processing and analysis of weak underwater signals.
Copyright (c) 2026 Tongjing Sun, Lei Chen, XiaoHong Deng https://creativecommons.org/licenses/by/4.0
Causality- and Passivity-Constrained Nonnegative Attention for Interpretable Structure-Borne Road Noise Prediction in Battery Electric Vehicles
In battery electric vehicles (BEVs), structure-borne road noise in the 20 Hz to 300 Hz band becomes more audible because the engine-masking component is largely absent, and conventional transfer-path formulations can be sensitive to suspension nonlinearity and ill-conditioned inversions. This paper presents a physics-informed, non-negative multi-modal fusion network (NN-MMFNet) that predicts in-cabin sound pressure from multipoint chassis excitations while keeping the mapping physically plausible and interpretable. The model combines a dual-stream encoder to separate transient impact signatures from steady resonance content with a strictly causal fusion/decoding pathway. A passivity-motivated spectral gain cap is applied to prevent non-physical amplification while preserving phase. To enable additive path attribution, the cross-modal attention weights are constrained to be non-negative. Training follows a sim-to-real workflow, using virtual-fleet pretraining and short fine-tuning on measured data. On a production BEV, NN-MMFNet reproduces the 20 Hz to 300 Hz spectrum with a 1.12 dB(A) global root mean square error (RMSE) at 60 km/h and a 0.14 dB error at the 128 Hz boom, outperforming transfer path analysis (TPA), frequency transfer matrix (FTM), and autoregressive moving average (ARMA) baselines. Impulse-response checks show a negligible passivity-violation rate (<0.01 %). The learned attention consistently points to a rear subframe-to-body mounting path near 128 Hz, and a targeted stiffness adjustment at this location reduces the measured cabin noise by 4.2 dB(A).
Copyright (c) 2026 Haijun Wang, Zhijie Huang, Zengjun Lu, Xianghua He, Tie Xu https://creativecommons.org/licenses/by/4.0
Dispersion Characteristics of SH waves in a Rotating Micro-structured Plate with Restrained Boundaries
Shear horizontal (SH) waves in plates are elastic stress disturbances that propagate along bounded surfaces, with in-plane shear motion perpendicular to the propagation direction, influenced by physical, geometric, and boundary conditions. Due to their sensitivity to surface and subsurface defects, SH waves are widely employed in non-destructive testing (NDT), structural health monitoring (SHM), and material characterization. This study presents a theoretical investigation of SH-wave propagation in a rotating, microstructural elastic plate within the framework of Consistent Couple Stress Theory (CCST), incorporating elastically restrained boundary conditions. CCST introduces a characteristic length parameter to account for microstructural and size-dependent effects beyond classical elasticity. Restrained boundaries provide an intermediate model between idealized traction-free and rigid conditions, capturing realistic boundary behavior encountered in practical applications. An analytical dispersion relation is derived to examine the combined effects of boundary restraints, microstructural parameters, and rotational speed on SH-wave dispersion, with several special cases presented to validate the general formulation. Graphical results illustrate the influence of restraint stiffness, characteristic length, plate thickness, and rotation on SH-wave dispersion characteristics. The findings offer valuable insights for the design of advanced sensing devices, the development of non-destructive evaluation techniques, and the analysis of seismic wave propagation in rotating geophysical layers.
Copyright (c) 2026 Mandeep Kaur, Satish Kumar, Vikas Sharma https://creativecommons.org/licenses/by/4.0
Flanking Sound Transmission in Massive-Lightweight Connections
Assessing the impact of flanking sound transmission is one of the most significant challenges in the process of designing building partitions. Acoustic parameters declared by manufacturers of lightweight systems are subject to errors of up to several decibels – and in the case of inaccurate construction on site, these differences can reach even higher values. One factor contributing to this is the phenomenon known as flanking sound transmission, which involves the transmission of acoustic energy through partitions connected to the partition directly dividing two adjacent rooms. For this reason, estimating the resultant acoustic insulation of a partition, taking flanking paths into account, is crucial at an early stage of the design process to ensure compliance with the requirements outlined in standard recommendations, and the literature. Currently, there are regulations and studies that provide guidance on calculating the estimated reduction in acoustic insulation due to flanking transmission. However, in practice, situations arise that have not yet been addressed in standards or the literature. Examples include partitions made of plasterboard, which are among the most common types of partition walls in Poland, yet are not covered by current normative procedures, as well as glass systems. This study aims to further explore this topic by analysing the impact of combining a massive partition with flanking lightweight partitions for selected structures (glass, plasterboard with single or double panelling, with full or partial sound-absorbing material infill, and without infill) and connection types.
Copyright (c) 2026 Agnieszka Wójtowicz, Tadeusz Kamisiński, Jarosław Rubacha https://creativecommons.org/licenses/by/4.0
Study on Dual-Stage Amplification Cascaded Piezoelectric Transducer for High-Power Applications
To reduce the size and enhance the efficiency of cascaded sandwich transducers with conical horns, a novel structural configuration of such transducers is investigated. This transducer incorporates two sets of piezoelectric stacks, enabling two-stage amplification to improve efficiency. An equivalent circuit model of the cascaded sandwich transducer with a conical horn is established, and analytical expressions for key performance parameters, including input impedance, velocity amplification ratio, and resonant characteristics, are systematically derived. Through theoretical and simulation analyses, the dynamic influence of key structural parameters on electromechanical energy conversion efficiency is determined, specifically including the output radius of the second stage, the relative position of the variable cross-sections of two sets of piezoelectric ceramic sandwich structures, and the spacing between the two sets of piezoelectric stacks. Furthermore, a performance optimization strategy based on piezoelectric single-crystal materials is proposed. Numerical simulation results, validated against the theoretical models, reveal the governing principles of piezoelectric material properties on transducer performance. Experimental results demonstrate excellent agreement between the operational characteristics of the optimized transducer and predictions obtained from both theoretical models and finite element simulations. This work provides significant guidance for the optimization of multi-mode transducers and demonstrates promising application potential in high-power ultrasonic fields.
Copyright (c) 2026 Guo Li, Peiyu Tan, Ruihui Ma, Feilong Li, Xiaoli Zhang, Hua Tian https://creativecommons.org/licenses/by/4.0
In Memoriam Professor Eugeniusz Kozaczka
Professor Eugeniusz Tadeusz Kozaczka, member of the Polish Academy of Sciences, passed away on May 27, 2025, in Gdynia. We write these words with profound sorrow and deep regret, mourning the loss of such an exceptional person as Professor Eugeniusz Kozaczka.
Copyright (c) 2025 https://creativecommons.org/licenses/by/4.0
Impact of Perforated Sheet Geometry on the Insertion Loss of Absorption Silencers
This study evaluates the influence of perforated sheet geometry on the acoustic and aerodynamic performance of absorption silencers. A modular silencer was developed, enabling the installation of six different perforated metal sheets with varying hole shapes (round, square, elongated), sizes (2-20 mm), and open area ratios (22-45%). Glass wool was used as the sound-absorbing filling. Insertion loss, self-noise, and pressure drop were measured in a large reverberation chamber, within the frequency range 50-10,000 Hz, for airflow velocities of 4, 6, and 8 m/s. The results indicate that all configurations provide comparable attenuation at low frequencies. Silencers with small round perforations (diameter 2-6 mm) ensured higher insertion loss and lower self-noise in the 1,000-5,000 Hz mid-frequency range, without any measurable increase in pressure drop compared to variants with larger or elongated holes. For frequencies above 6,300 Hz, perforated sheets with larger holes performed better. Pressure loss differences between all configurations did not exceed 1 Pa at a given flow velocity. The results confirm that aperture size is the primary parameter affecting silencer acoustic effectiveness, while aperture shape and perforation ratio are secondary. These findings provide practical guidelines for optimal silencer design in ventilation systems, ensuring maximum noise reduction with minimal airflow resistance.
Copyright (c) 2026 Kamil Wójciak, Joanna Maria Kopania, Patryk Gaj https://creativecommons.org/licenses/by/4.0
Analysis on Modal Distribution and Modal Density-Based Crossover Frequency in Cabin-Sized Enclosures
In the sound field simulation of cabin-sized enclosures, the Schroeder frequency (SF) is still employed to estimate the crossover frequency (CF) that determines the validity ranges of wave-based and geometrical acoustic methods. However, because cabin-sized enclosures exhibit distinct modal behaviors from typical medium- and large-scale rooms, the validity of SF in such enclosures has not been thoroughly tested. This study introduces the modal density-based crossover frequency (MDCF) to systematically evaluate the applicability of SF in cabin-sized enclosures. The MDCF employs the same dense modal criterion as SF. However, its modal parameters, are derived from the numerical eigenfrequency analysis. This contrasts with the SF formula, where these parameters are determined solely by the room volume and reverberation time. Ten models are constructed for evaluation, grouped into two volume sets: 8 m3 (cabin-sized) and 80 m3 (common-sized). Each set comprises five distinct geometrical shapes from rectangular models to simplified vehicle shapes. The results reveal that, for cabin-sized enclosures under low absorption boundary conditions, the MDCF is typically 70 Hz to 150 Hz lower than SF; the discrepancies decrease to 20 Hz to 50 Hz in 80 m3 rooms. Furthermore, the MDCF varies with room shapes at a constant volume, while the SF remains nearly unchanged. These findings demonstrate that MDCF provides a more reliable CF estimation for rooms with irregular shapes, highlighting the importance of considering accurate modal parameters in the acoustic analysis of cabin-sized models.
Copyright (c) 2026 Ziyu Wang, Liangfen Du, Guangzheng Yu https://creativecommons.org/licenses/by/4.0
TimeGAN and Coordinated Attention Prototype Network Based Prediction Model for Infrasound Signal
Due to the complexity of the infrasound environment and the high costs associated with data collection, frequent acquisition of infrasound data is often impractical, resulting in a limited amount of labeled data. To address the challenge of low classification prediction accuracy caused by data scarcity, this paper proposes an infrasound prediction model based on a time-series generative adversarial network (TimeGAN) and coordinated attention prototype network (CAPN) (TimeGAN-CAPN). The model begins by introducing TimeGAN, where the generative network is trained using a combination of unsupervised and supervised learning. This approach enables the network to operate within the latent space of temporal features and generate time-series data that closely aligns with the distribution of the original data. These generated samples are then combined with the original data to form an augmented dataset. Subsequently, the augmented data is input into the CAPN, which enhances the sample size per class, allowing for more precise class prototypes and improving the prediction accuracy of the model. Furthermore, the quality and diversity of the data generated by TimeGAN are quantitatively and qualitatively assessed using maximum mean discrepancy (MMD) and t-distributed stochastic neighbor embedding (t-SNE), facilitating a comparison and verification of the generated data’s performance. Experimental results show that TimeGAN-CAPN significantly outperforms the CAPN model in classification tasks with limited infrasound data, achieving an increase in accuracy of 7.15 %. This demonstrates that the proposed method is highly effective for predicting infrasound-related disasters, particularly in scenarios with small sample sizes.
time-series generative adversarial network
Copyright (c) 2026 Quanbo Lu, Xiaojuan Huang, Rao Li, Mei Li, Dong Zhu https://creativecommons.org/licenses/by/4.0
An Empirical Approach to Investigate Environmental Effects on Acoustic Signal Speed in Oceanic Layers
This paper investigates and demonstrates the effects of three significant environmental contributors: temperature, depth and salinity impact on the acoustic signal propagation across distinctive ocean layers: mixed, thermocline, and deep layers. In the field of underwater wireless sensor networks (UWSN), exact and precise determination of coordinates for sensor localization is very crucial for data validation. Temperature dominates the upper layers; depth becomes the prime factor for the deeper domain with minimal thermal variations. Salinity while having a diminished effect, facilitates minor changes in propagation and deviation of acoustic signal speed. In our work we have analyzed these interdependencies by using different empirical models (e.g., Mckenzie, Medwin) customized to each layer, accounting to their incomparable environmental parameters. In mixed layers, changes in sound speed are mainly caused by thermal factors, where depth is of minimal importance, and the influence of salinity is insignificant, but with increasing depth, the temperature begins to decrease, and depth (pressure) begins to become important, and changes in salinity and temperature become almost equivalent. By evaluating ocean layer specified empirical formulas, we have calculated the average speed of sound and measure the corresponding contribution of all parameters. Our work has provided a substructure which helps to optimize the identification or localization of UWSN nodes. The results of this work underscored the essential to have an adaptive sound speed modeling in order to achieve enhanced and precise acoustic signal communication systems.
Copyright (c) 2026 Khondoker Munim Salehin, Md. Khalid Mahbub Khan, Anisur Rahman https://creativecommons.org/licenses/by/4.0
Ultrasonic Estimation of Pressure Dependent Non-Linearity Index in Liver
This study introduces a proof-of-concept methodology for evaluating pressure-dependent non-linear acoustic properties of liver tissue. The proposed non-linearity index (NLI) is derived from echo amplitudes obtained at two substantially different acoustic pressures. Unlike previous harmonic-based approaches, the method relies solely on the fundamental frequency band, allowing clinical implementation without additional system modifications. The image acquired for the lower pressure is then amplified to correct for the pressure difference between the beams. Next, the NLI is estimated as a ratio of local amplitudes of the amplified low-pressure image (ALPI) to the high-pressure image (HPI). In the case of nonlinear media some energy of the wave is transferred from the pulse fundamental frequency to higher harmonics, which affects mainly the HPI. With the harmonics being filtered out from the signal, the HPI amplitude becomes lower than the ALPI amplitude. As a result, the NLI becomes higher than 1 and increases with the non-linearity of the imaged tissue. The hydrophone measurements were compared to the simulation (k-Wave) of the ultrasonic field in water and vegetable oil. Next, we performed NLI imaging of healthy and fatty livers using SonixTouch (Ultrasonix) systems and two acoustic pressures of 390 kPa and 1590 kPa. Preliminary studies – imaging healthy and fatty livers using SonixTouch (Ultrasonix) systems were performed on the 4 livers of the authors of the article showed that for ‘healthy’ livers the NLI was below 1.1, while in one of the authors with previously diagnosed steatosis falling between score 1 and 2, the NLI locally exceeded 1.3. These results show that the obtained NLI values increase with the degree of steatosis, which agrees with theoretical expectations based on tissue B/A coefficients. The work emphasizes methodological feasibility and physical consistency rather than clinical validation, given the limited number of volunteers and ethical restrictions on patient recruitment.
Copyright (c) 2026 Andrzej Nowicki, Jurij Tasinkiewicz, Piotr Karwat, Norbert Żołek, Ihor Trots, Ryszard Tymkiewicz https://creativecommons.org/licenses/by/4.0
Few-Shot Transfer for Speech Enhancement Using SEGAN with Stability Guardrails
High-quality speech communication is often compromised by background noise, reducing intelligibility and perceived quality. We investigate data-efficient few-shot transfer of a Speech Enhancement Generative Adversarial Network (SEGAN) to a new noise domain. Starting from a generator pretrained on VoiceBank–DEMAND, we adapt the model to MiniLibriMix using only 300 paired noisy–clean examples. To prevent overfitting and catastrophic forgetting, we introduce SAFE (Stable Adversarial Few-shot Enhancement), a three-fold stabilisation strategy with (i) exponential-moving-average (EMA) weight averaging, (ii) L2-SP weight anchoring to the source-domain parameters, and (iii) a teacher–student consistency loss. SAFE maintains VoiceBank performance (PESQ ≈ 1.84; STOI ≈ 90 %) and, after an optional perceptual fine-tuning stage (MR-STFT + adversarial), yields substantial target-domain gains on MiniLibriMix (PESQ 1.11 → 1.26, STOI 71.5 % → 81.5 %) with only a minor source-domain trade-off in STOI. Ablation experiments demonstrate that EMA provides the strongest stabilising effect, while L2‑SP and consistency regularisation offer complementary benefits. These results suggest that stable few‑shot adaptation can make lightweight time‑domain speech enhancers practical for rapid deployment in novel acoustic environments.
Copyright (c) 2026 Rubi Sharma, Firos A. https://creativecommons.org/licenses/by/4.0
Application of Acoustic Metamaterials in the Design of Muffling Unit of Internal Combustion Engine
Aiming at the problems of large volume, high exhaust resistance and difficulty in suppressing noise in the 500 Hz to 100 Hz frequency band of traditional internal combustion engine exhaust mufflers, a noise reduction unit design based on acoustic metamaterials is proposed. Based on the equivalent medium theory, an acoustic model with a ring structure and multi-region variable refractive index was established. Phase control is achieved by helically winding the acoustic channel to change the refractive index, and the basic dimensions of the acoustic metamaterial muffling unit are calculated. The sound field distribution, transmission loss and flow field characteristics of the muffling unit are simulated and analyzed. This structure utilizes a multi-layer acoustic channel structure, effectively alleviating the problem of insufficient low-frequency noise elimination caused by the asymmetry of Fano interference. It achieved a transmission loss of over 10 dB within 85 % of the 500 Hz to 1000 Hz frequency band, and still maintained excellent noise reduction performance under high-frequency conditions through multi-level phase control. By connecting multiple units in series, a transmission loss of 10 dB can be achieved within 85 % of the 500 Hz to 1000 Hz frequency band. The exhaust flow field of the muffling unit was simulated and analyzed. Whether used alone or in series with the traditional muffling structure, the exhaust resistance remained within the range of 360 Pa to 370 Pa. Experimental tests show that when the metamaterial muffler unit is used in combination with the traditional muffler, it effectively achieves targeted noise elimination in the 500 Hz to 1000 Hz frequency band, and also demonstrates clear noise reduction capabilities in higher frequency ranges. The high noise suppression characteristics, high gas passage characteristics and compact volume characteristics of this structure provide more potential analysis methods and design schemes for the research and development of internal combustion engine mufflers and noise reduction accessories.
Copyright (c) 2026 Tianshuo Li, Lei Zheng, Zhengyang Bi, Hongchao Ji https://creativecommons.org/licenses/by/4.0
Modeling and investigation of a multi-resonant metamaterial sound insulator
A design of multi-resonant acoustic metamaterial sound insulator is proposed to attenuate multi-tonal and broadband noise. The unit cell of the metamaterial consists of a porous material with four, nine, and sixteen embedded Helmholtz resonators and its sound attenuation performance is studied using finite element method (FEM). A theoretical approach based on transfer matrix method is proposed and the theoretical results of the sound absorption and the transmission loss (TL) agree well with FEM results. Compared to the porous layer with one embedded resonator that presents one TL and one sound absorption resonant peak, the metamaterial made of four, nine, and sixteen embedded resonators exhibits respectively four, nine and sixteen sound absorption and TL resonant peaks. The sound absorption at various incidence angles and the diffuse field sound absorption of the proposed metamaterial are studied. At each resonant frequency, the acoustic pressure is maximum in the cavity of the corresponding resonator while in the associated neck, the acoustic velocity is maximum with important acoustic power dissipation density. As the incidence angle increases, the acoustic pressure in the cavity at the resonant frequencies decreases as well as the velocity in the necks and the power dissipation density becomes negligible, resulting in a decrease of the sound absorption. As the number of resonators within the porous layer increases, the sound absorption and TL frequency band enlarges. Compared to the conventional porous layer, the sound absorption and the TL are significantly improved at the resonant frequencies of the resonators.
Copyright (c) 2026 Zacharie Laly, Raymond Panneton, Noureddine Atalla, Sebastian Ghinet https://creativecommons.org/licenses/by/4.0
Subwavelength Underwater Imaging of a Wire Array Metamaterial Based on Fabry–Perot Resonance
Metamaterials with Fabry–P´erot (FP) resonance have proven effective for underwater ultrasound imaging. The propagation phenomenon can be understood as a spatial filter with linear dispersion over a finite bandwidth. However, conventional imaging techniques are constrained by the diffraction limit or rely on a strong impedance mismatch between the metamaterial and water. In this paper, we propose a columnar array metamaterial designed for underwater imaging based on FP resonances and validate the proposed design through numerical simulations. The acoustic pressure transmission coefficient, together with the normalized acoustic pressure distribution, is analyzed to quantitatively evaluate imaging quality and verify the physical effectiveness of the model. This novel structure enables deep subwavelength imaging underwater, maintaining excellent and stable imaging performance within a 0.4 kHz bandwidth centered around the operating frequency. We use air-filled metamaterials to create strong acoustic coupling and establish effective sound isolation. This approach significantly enhances imaging resolution, while optimizing energy loss at multiple interfaces, an issue in previous studies. Additionally, in contrast to resonance- or refraction-based approaches such as Helmholtz resonators or hyperlens designs, the proposed FP-resonant metamaterial offers an alternative mechanism for achieving near-field subwavelength imaging through controlled wave transmission and confinement. We also examine the influence of various parameters, such as imaging distance, incidence distance, and array periodicity, on imaging performance. The results demonstrate that the columnar array metamaterial holds great potential for underwater ultrasound imaging applications.
Copyright (c) 2025 Guo LI, FeiLong LI, LiQing HU, QunFeng LI, GuanJun YIN https://creativecommons.org/licenses/by/4.0
Development of Sustainable Lightweight Acoustic Composites from Denim, Flax, and Hemp Fibers
The textile and clothing industries pose a serious problem in terms of environmental sustainability as they are among the sectors that produce the most waste worldwide. In this context, recycling both pre-consumer and post-consumer clothing waste into composite materials is of great importance in terms of both waste management and material science. In this study, composite panels were developed using waste denim fabrics in different natural fiber compositions, recycled flax fibers derived from waste linen fabrics, and virgin hemp fibers as reinforcement materials. Polypropylene/polyethylene nonwoven interlining waste served as the matrix material, and panels were fabricated by hot pressing at two different reinforcement/matrix ratios. Acoustic properties were evaluated through sound absorption coefficient (SAC), noise reduction coefficient (NRC), and sound transmission loss (STL) measurements. In the case of denim waste, the results showed that flax or hemp blended samples provided better sound absorption than 100% cotton, especially at low matrix ratio. For the rest, while pure flax samples absorbed sound well, pure hemp samples showed good barrier properties with high transmission loss.
Copyright (c) 2026 Nazan Okur, Canan Saricam https://creativecommons.org/licenses/by/4.0
Similarity Analysis and Target Strength Correction of Non-Proportional Scaled Models Based on Highlight Model Theory
Acoustic scattering scale models often fail to meet the acoustic similarity design requirements due to limitations in fabrication technology, testing facilities, and safe transportation, which restrict the accurate extrapolation of acoustic scattering characteristics between scaled models and full-scale ships. To overcome this challenge, the present study applies highlight model theory to perform acoustic similarity analysis and to correct the local target strength of simple objects in the model based on overall acoustic scattering correction. A novel method for correcting the target strength of non-proportional scaled models is proposed. The method is validated using various model geometries, including ellipsoids, finite-length cylinders, truncated elliptical cones, and complex structures. Additionally, the plate element method is employed for target strength correction and scaling conversion analysis for non-proportional scaled models. The study highlights the variation in target strength due to changes in geometric dimensions and demonstrates the effectiveness of the proposed correction method. The results indicate that the proposed correction approach allows for more accurate extrapolation of target strength from non-proportional scaled models to full-scale prototypes, thereby better satisfying the requirements of practical engineering applications.
Copyright (c) 2026 Jin Zhang, Zhenyu Li, Yinhao Li, Zilong Peng https://creativecommons.org/licenses/by/4.0
Application of ISO 12913 Standard to Assess Urban Soundscapes: A Case Study on Poznań
ISO 12913 standards provide a unified framework for describing and assessing soundscapes, however, the lack of a Polish translation has so far limited their practical use. This paper presents the first application of a validated Polish version of the ISO/TS 12913-2 perceptual attributes, enabling full cross-language comparability of results. Whereas Polish research has traditionally focused on noise annoyance and broad judgements of acoustic comfort or discomfort, we outline the complete ISO-compliant assessment procedure, which combines: a soundwalk, questionnaires and audio-visual recording. The study was conducted at eight diverse urban locations in Poznań, Poland. Participants rated the soundscapes using eight attributes: przyjemne, tętniące życiem, bogate w wydarzenia, chaotyczne, dokuczliwe, monotonne, ubogie w wydarzenia, spokojne. Each rating set is mapped to a point in the 2D pleasantness-eventfulness space defined in ISO/TS 12913-3, facilitating visual comparison of locations and the identification of design needs. Results reveal pronounced perceptual differences between spatial typologies and demonstrate that the standardized approach provides richer, multidimensional information about the acoustic environment than conventional noise indicators. The proposed methodology establishes a reference framework for Polish soundscape studies and can support the creation of more people-friendly urban acoustic environments.
Copyright (c) 2026 Jakub Dumanowski, Anna Preis, Jan Felcyn https://creativecommons.org/licenses/by/4.0
Single-Sensor Passive Ranging of Underwater Monopoles Using Near-Field/Far-Field Energy Contrasts
While acoustic vector sensors (AVS) are well-established for detection and direction-of-arrival (DOA) estimation using co-located pressure and particle motion (PM) measurements, their potential for passive range estimation remains largely unexplored. This paper introduces a novel single-AVS method for passive range estimation to an acoustic monopole source by exploiting the fundamental near-field dominance of PM energy. We derive the frequency and the distance dependent ratio (ξ) of kinetic to potential acoustic energy density – a key near-field signature inaccessible to conventional hydrophones. By leveraging simultaneous AVS pressure and PM velocity measurements, our method estimates ξ, inverts the monopole near-field model to obtain the Helmholtz number, and directly computes the range. Crucially, we demonstrate that PM sensors offer a potential signal-to-noise ratio (SNR) advantage over pressure sensors within the near-field (>7.8 dB). Validation under simulated noise conditions shows accurate range estimation (RMSE <10 %) for low-frequency sources (<100 Hz) within 8 m–25m ranges at 0 dB SNRs, with performance degrading as frequency increases or SNR decreases. Critically, robustness is confirmed using recorded basin noise profiles, overcoming the isotropic Gaussian noise assumption. This technique extends AVS functionality beyond DOA, enabling single-sensor passive ranging without arrays, environmental priors, or reference signals where conventional methods fail.
Copyright (c) 2025 Saier MAHMOUD, Louay SALEH, Ibrahim CHOUAIB https://creativecommons.org/licenses/by/4.0
Analysis of Decision Fusion in Speech Detection
This article addresses the issue of detecting speech signal segments in an acoustic signal and analyzes potential decision fusion for a group of voice activity detectors (VADs). We designed ten new VADs using three different types of neural network architectures and three time-frequency signal representations. One of the proposed models has higher classification efficiency than competitive solutions. We used our VAD models to analyse data fusion and improve the final classification decision. For this purpose, we used gradient-free and gradient-based optimizers with different objective functions. The analysis revealed the impact of individual classifiers on the final decisions and the potential gains or losses resulting from VAD fusion. Compared with existing models, the models we proposed achieved higher classification accuracy at the cost of increased memory requirements. The final choice of a specific model depends on the platform constraints on which the VAD system will be deployed.
Copyright (c) 2025 Tomasz MAKA, Lukasz SMIETANKA https://creativecommons.org/licenses/by/4.0
Active Vibration Suppression of a Thin Circular Pipe
The article presents an active vibration damping system for a thin-walled cylindrical tube, which is a simplified model of a lightweight robot (LWR) arm. The proposed solution integrates control algorithms, piezoelectric materials and a hardware and software environment enabling real-time control. Macro fiber composite (MFC) elements were used for active vibration reduction, acting simultaneously as sensors and actuators. The object on which the research was conducted was a tube with an external diameter of 40 mm, this element was rigidly mounted at a distance of 1 meter from the free end, simulating cantilever conditions. The stimulation of the object to vibration was carried out using the MFC actuator, while the system response was recorded in the xPC Target environment. Based on the measurement data, the mathematical model of the object was identified in the discrete domain using the ARX method. The obtained model was used to design a controller based on the pole location method, which was implemented on a real test stand. The experimental results showed the effectiveness of the designed control system in reducing the amplitude of natural vibrations of the structure. The use of MFC elements as sensor elements and actuators enabled effective vibration damping in real time, confirming the usefulness of the proposed solution in the context of improving the precision of robotic systems.
Copyright (c) 2026 Marcin Pater, Lucyna Leniowska, Marcin Grochowina https://creativecommons.org/licenses/by/4.0