Temperature-dependent characterization of nanomaterials is commonly performed through electrical measurements, and many temperature-sensing applications similarly rely on electrical readout signals. Although these approaches are simple and widely used, they require direct sample contact and may lose sensitivity when the electrical response is weak, saturated, or only weakly dependent on temperature. In this study, a photoacoustic (PA) measurement system was used to evaluate the temperature-dependent response of AgNW networks. PA measurement system detects ultrasonic waves generated through transient thermoelastic expansion after optical absorption, which enables sensitive probing of temperature-dependent optothermal responses beyond conventional electrical measurements. Silver nanowire (AgNW) films with different surface coverage were fabricated through one to four repeated spin-coating cycles using a 1% AgNW ethanol dispersion containing nanowires with diameters of 20–40 nm and lengths of 10–20 µm. The photoacoustic (PA) signals of the fabricated films were measured at various temperatures using a customized PA measurement system and were compared with sheet resistance values obtained using a four-point probe. Both sheet resistance and PA signals increased with increasing temperature, regardless of AgNW surface coverage. Notably, AgNW films with higher surface coverages showed only weak temperature dependence in sheet resistance but pronounced temperature-dependent PA response. These results indicate that PA analysis is particularly useful for characterizing AgNW networks with higher surface coverage, including those used in stretchable electrodes. All samples showed linear relationships for both sheet resistance and PA signals, with coefficients of determination (R2) exceeding 0.9. Overall, these findings suggest that PA measurement may provide complementary information on temperature-dependent behavior that is not fully reflected in sheet-resistance measurements.
In this paper, a modal decomposition method is employed to analyze the properties of Rayleigh–Lamb waves propagating in an isotropic plate containing an open surface-breaking crack. The mode conversion coefficients (MCCs) are calculated as functions of crack depth and ultrasonic frequency for both an incident Lamb wave. Compared with the incident A0 mode, the MCC of the S0 mode exhibits a less smooth dependence on the phase of the crack modulated. The experimental, finite element method (FEM) and analytical results confirm that crack characteristics can be quantitatively evaluated from the Lamb wave mode conversion indued by the crack. This finding is beneficial for interpreting the detected ultrasonic signals in scenarios involving crack measurements between different waves, such as the modulation of the probing wave’s MCC by the material response in a tensile test machine.
Acoustic vehicle classification from roadside microphones supports source-specific traffic noise monitoring, but classifiers trained on one dataset generalize poorly to recordings from different environments. This study compares pre-trained audio transformers (BEATs, AST) against a CNN baseline for cross-dataset vehicle classification into five categories (car, truck, motorcycle, bus, background), training on the IDMT-Traffic dataset (Germany) and testing on the MELAUDIS dataset (Australia). Two domain adaptation methods (DANN, ArcFace) are applied to the best-performing transformer. BEATs achieves a balanced F1 of 0.46, a 77% improvement over the CNN baseline (0.26). AST achieves F1 = 0.43, a 65% improvement. Both pre-trained transformers substantially outperform the baseline, with self-supervised pre-training producing slightly more transferable representations than supervised pre-training. ArcFace metric learning achieves the highest cross-dataset F1 (0.50), modestly outperforming standard fine-tuning. DANN degrades cross-dataset performance but achieves the highest microphone robustness score (F1 = 0.80). Classification of the underrepresented bus class (53 training samples) improves from F1 = 0.38 to 0.54 with ArcFace. Microphone robustness is strong across all models (BEATs F1 = 0.75), confirming that recording environment dominates the domain shift over hardware variation. The choice of domain adaptation strategy should be guided by the expected type of domain shift.
Broadband, low-frequency sound absorption within a compact device remains a central unsolved problem in noise control engineering, arising from fundamental trade-offs among resonator volume, absorption bandwidth, panel thickness, and frequency tunability that no passive, linear, time-invariant system can simultaneously circumvent. This review establishes a unified mass–spring–damping (MSD) framework applied systematically across the full spectrum of resonance-based absorber technologies. From first principles, we derive the mass–stiffness coupling result (the mass-disappearing result of Shen and Liu): fixing the resonance frequency imposes K=Mωres2, so acoustic mass and stiffness cannot be adjusted independently; the half-absorption bandwidth Π1=η/(Mωres)+Vωres/(c0Star) then depends explicitly on the cavity volume V (system stiffness) and on the damping coefficient η, rather than on mass as an independent lever. This explains why neck extension, space-coiling, and membrane loading—which merely add mass while leaving the cavity stiffness unchanged—fail to broaden the absorption band at fixed volume, and refocuses the design effort on stiffness reduction and damping control. Five non-dimensional performance metrics are introduced that collapse the scattered literature into a single, scale-independent language for rigorous comparison across all absorber families: normalised half-absorption bandwidth Π1, volume efficiency Π2, integral absorption criterion Π3 tied to the Rozanov causality bound, quality factor Q=1/Π1, and frequency-thickness ratio Π4. A two-degree-of-freedom acoustic–structural coupling model yields closed-form effective stiffness and damping, revealing how structural loss augments acoustic damping, how modal veering produces split absorption peaks, and how the anti-resonance frequency becomes a designable parameter. A critical distinction is drawn between mathematical negative stiffness (a fitting artefact) and physical negative stiffness via repulsive magnets, bistable elements, or negative-capacitance piezoelectric shunts, which genuinely reduces cavity stiffness, lowers resonance frequency, and widens bandwidth beyond the passive causality bound. The shunt electromechanical diaphragm further demonstrates α>0.9 at nine tonal frequencies spanning three octaves without mechanical modification. Finally, embedding MSD equations and Π1–Π4 bounds as hard physical priors in AI/LLM-assisted design frameworks is identified as the key step toward provably physically consistent absorber synthesis.
In the context of temporary urban environments such as festivals and construction sites, acoustic discomfort inside textile-based party tents remains a critical yet under-addressed issue. This study, developed in collaboration with industrial partners from the construction and textile sectors, aimed to design and assess lightweight, flexible sound-absorbing solutions capable of improving acoustic comfort while reducing environmental impact. A set of nine composite textile samples were fabricated using combinations of recycled and technical materials. Their acoustic behavior was characterized through standardized laboratory tests (ISO 10140-2 and ISO 354:2004) and full-scale prototypes under simulated real-world conditions. Simultaneously, a Life Cycle Assessment (LCA) was conducted according to ISO 14040:2006 and EN 15804:2020 standards to quantify environmental impacts from cradle to gate. The results demonstrate that it is possible to achieve an effective balance between acoustic performance and environmental sustainability. Integrating both types of assessment into the material selection process enables more informed, responsible design decisions for temporary textile structures, aligning construction practices with growing demands for functional and sustainable solutions.
Research on acoustic vases embedded in historical buildings has progressively developed through archaeology, architectural history, and acoustics, producing extensive documentation on their distribution, geometry, installation and possible acoustic role, with experimental evidence from in situ measurements, laboratory tests, and numerical analyses. However, documentation and measurement procedures remain highly heterogeneous, limiting reproducibility and comparative interpretation. Within this context, the present work proposes a preliminary methodological framework for future investigations. It reviews the principal European documentation, census, experimental, and numerical approaches identified by the authors. Particular attention is given to the recording system developed by Palazzo-Bertholon and Valière and to the experimental methodologies adopted in previous studies, including procedures, acoustic descriptors, and instrumentation. A possible extension of the “fiche d’information” is discussed to make geometrical, spatial, and installation-related data more explicit for comparative analyses, acoustic modelling, and measurement planning. A documented case study is used to illustrate the proposed organization of information, followed by a simplified acoustic simulation showing how structured data may support model construction and interpretation. The proposed procedure therefore combines simulation and in situ measurements, with standard and advanced investigation levels. The study is aimed at improving documentation quality, consistency, and comparability rather than providing definitive evidence of acoustic effectiveness.
Underwater communication is essential for marine research, yet saline environments pose significant challenges as electromagnetic waves suffer from severe attenuation and optical systems face scattering. Consequently, acoustic transmission remains the most practical method for medium- to long-range communication. This study investigates the impact of salinity, transmission frequency, and propagation distance on signal integrity, specifically focusing on the feasibility of using a square-wave carrier with On-Off Keying (OOK) modulation as a simpler, low-cost alternative to traditional sinusoidal frequency-shift keying (FSK). Experiments were conducted in a custom glass tank and analyzed via MATLAB. The results reveal that increased salinity and higher frequencies led to greater signal distortion and attenuation, which complicates reliable binary recovery. However, despite these environmental hurdles, the study demonstrates that square-wave OOK allows for successful binary data recovery over short distances. The findings suggest that simplified modulation schemes could potentially be used for short-range underwater communication in controlled environments, particularly where minimizing system complexity is of concern. Ultimately, the work provides valuable insights into how environmental factors influence acoustic signal integrity, offering a preliminary basis for future development of accessible and efficient underwater communication platforms targeted to shallow water communication.
Ceramic Matrix Composite (CMC) are widely used in aerospace due to the advantages such as high-temperature resistance and lightweight properties. Detecting defects within these materials is crucial for ensuring the safety of corresponding structures. In this paper, a finite element model of CMC model for layered structures is established for the ultrasonic non-destructive testing. Based on the computed tomography (CT) scan images and porosity of the material, a randomly distributed pore model is constructed to investigate the effect of pores on the ultrasonic signals. Random pores are also introduced in the simulation to ensure that the model corresponds as closely as possible to reality. Moreover, the feasibility of utilizing air-coupled ultrasonic excitation to generate specific frequency Lamb waves is verified. The effect of pore presence on the signal propagation is analyzed, and the effects of layered structures at different positions and lengths on the signal propagation are investigated. The results demonstrate that the Lamb waves with a specified frequency can be excited using the method described in this paper, and the presence of pores and delamination defects can affect the propagation of the Lamb wave in CMC, in which the signal attenuation can reach up to 7.6 dB.
Reflection silencers are installed in the exhaust system of stationary combustion engines to attenuate low-frequency noise by means of destructive interference. The acoustic properties of mufflers are experimentally determined by the standard two-load method, which only considers measurements without mean flow. In real engine operation, however, exhaust mass flow is always present. Measurements are significantly more complex and expensive if fluid flow is taken into account, which is why the available data is limited. Thus, the impact of mean flow on the attenuation of silencers is not clearly known yet. This work contributes to the state of the art by quantifying the influence of the Mach number on the transmission loss of double-tuned straight-through mufflers based on reproducible, noise corrected measurement results that include uncertainties. A frequency range between 20 Hz and 891 Hz is investigated at eleven different Mach numbers between 0 and 0.1 under ambient conditions. It is found that resonance peaks diminish with increasing Mach number, while other frequencies remain unaffected by mean flow. These findings can be transferred to operating conditions of stationary combustion engines and other exhaust systems. The experimental data will serve as a basis for the validation of analytical and numerical models in subsequent work.
Class II biological safety cabinets (BSCs) are designed to protect the user, the product, and the laboratory environment by maintaining HEPA-filtered airflow; however, their fans, alarms, and structural resonances introduce acoustic and vibrational stimuli that may confound mechanosensitive cell-culture assays. In this study, we characterized the vibroacoustic environment of a cell-culture laboratory and a Class II BSC, selected representative tray locations based on measured and modeled stimuli, and evaluated in vitro wound closure in HaCaT keratinocytes using a scratch assay under alarm-induced acoustic exposure. Wound closure after 24 h was quantified using a relative area-closure metric defined as one minus the ratio of wound area at 24 h to wound area at 0 h. For each biological replicate (one flask and one scratch), two non-overlapping image regions were treated as technical subsamples and averaged to obtain a single flask-level value. Three independent experimental runs were performed, each including one flask per tray point, yielding n equals 3 independent flasks per tray point. Mean wound closure values were 73.7 percent plus or minus 15.6 percent, 75.6 percent plus or minus 7.2 percent, and 79.4 percent plus or minus 14.8 percent for tray points P1, P5, and P6, respectively (mean plus or minus standard deviation). No statistically significant differences were detected among points (one-way ANOVA on flask-level values, F equals 0.15, p equals 0.86). These findings highlight that BSC-associated acoustic and vibration stimuli should be documented when interpreting scratch-assay outcomes and motivate larger, sham-controlled studies to resolve small effect sizes relevant for assay reproducibility.
Enhancing the vibroacoustic performance of underwater vehicles remains a critical challenge in marine engineering. Increasing geometric stiffness is a conventional strategy to suppress vibration, yet its effectiveness in reducing underwater sound radiation can be practically limited. This paper presents a numerical investigation of the vibroacoustic response of composite grillage sandwich structures, with a focus on separating the contributions of geometric stiffening and core damping. A coupled acoustic structural model is developed based on the equivalent single layer theory and implemented in a finite element framework, then validated against analytical benchmark solutions. The parametric study reveals a stiffness saturation phenomenon in the acoustic domain. Although increasing rib height significantly reduces the mean square velocity, the radiated sound power reaches a saturation plateau and can even show a slight rebound at higher frequencies. This behavior is attributed to an increase in structural phase velocity that shifts modal components toward a more efficient radiation regime, thereby increasing radiation efficiency. To address this limitation, the damping modulation role of the core material is examined. The results show that introducing a high damping core into the grillage skeleton suppresses broadband noise and resonance peaks, without a comparable rise in radiation efficiency that may accompany geometric stiffening. The study indicates that a hierarchical synergistic design strategy that uses geometric stiffness for load bearing and low frequency control, while leveraging core damping to mitigate the acoustic saturation limit, provides useful physical insight into more efficient noise control approaches than purely stiffness based approaches.
Diocletian’s palace with its cellars represents one of the most important cultural heritage sites of the ancient Roman civilisation on the present-day Croatian territory. The cellar complex has been rediscovered only recently and has been preserved remarkably well due to its centuries-long concealment beneath mediaeval urban matrices. An archaeoacoustic analysis was performed on a selected single-nave hall as a small part of this complex. A model of the hall was developed in room acoustics simulation software and calibrated based on the results of field measurements. Acoustic suitability of the hall for speech-based events and music performances was then evaluated according to contemporary objective criteria, and the findings were compared with the results of similar studies performed on other heritage sites. The hall was found to be very well suited for speech in terms of intelligibility and mid-frequency reverberation, thus showing potential for revitalisation, with excessive low-frequency reverberation in the hall and reduced audibility in the farthest part of the audience as potential issues. With a feasible audience size, the hall is not reverberant enough for music performances but provides high clarity. In terms of sound strength, the hall is suitable for solo performers or small ensembles. Excessive perceptive broadening of the sound source is expected due to strong early lateral energy. In terms of traditional Dalmatian a cappella singing, the acoustics of the hall are likely to support and enhance such performances.
This systematic review summarizes experimental studies in atmospheric acoustics that quantify environmental influences on long-range sound propagation. A keyword-based search was conducted in Scopus and Google Scholar to identify relevant records. Studies were included if they were published in English between January 1977 and April 2026, investigated long-range sound propagation within the human audibility range using specific sound sources, and incorporated concurrent meteorological measurements. Two reviewers worked independently to assess eligibility of the studies included in this review. Following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines, this systematic review surveys the methodological content of these studies with respect to sound sources, signal content and processing, microphone configuration, treatment of the ground and topography, and meteorological measurements to identify common practices. Some studies provide only limited information about the acoustic source properties, postprocessing of acoustic data, and/or configuration of meteorological measurements. Key experimental details for the 40 included studies are tabulated and summarized via histograms for reference. Most experimental acoustic studies have measured propagation within a range of 2 km on relatively flat land and have utilized tower-based meteorological measurements. The results of the studies surveyed here have implications for understanding long-range outdoor sound propagation, including development of accurate numerical models. Some contributing authors were funded by the Office of Naval Research: ONR Award N00014 24-1-2400, ONR Award N00014-24-1-2437.
An approximate analytical model for the variation of A-weighted broadband sound levels with distance over flat acoustically soft ground from a source of known sound power depends on the reduction in low frequency content in noise spectra due to A-weighting. Also, it assumes a weak linear sound speed gradient and a frequency independent attenuation coefficient for air absorption. The model introduces adjustable frequency independent parameters for ground effect, turbulence and atmospheric refraction. An additional parameter allows for the source being located over acoustically hard ground. Predictions of the model are compared with measurements over several ground surfaces. The approximate model predicts a more rapid reduction in sound attenuation due to ground effect with increasing mean propagation path height than the simplified method in a widely used international standard. Moreover, predictions of A-weighted sound levels from onshore wind turbines using the approximate analytical method compare with data and numerical simulations better than the simplified and octave band methods in the international standard and the Swedish standard method.
The rapid progress of generative speech synthesis and voice-cloning technologies has enabled the creation of highly natural synthetic voices that pose a serious threat to telecommunication security. While most prior studies evaluate human ability to detect audio deepfakes using high-quality, studio-grade recordings, little is known about how real-world telecommunication channels affect perceptual detection. This study investigates the influence of three transmission scenarios—GSM (AMR-NB), VoLTE (AMR-WB), and VoIP with packet-loss modeling—on the human ability to distinguish natural speech from AI-generated speech. A custom speech corpus was developed, consisting of natural recordings from nine speakers and corresponding synthetic utterances generated using a state-of-the-art voice cloning system (ElevenLabs). All samples were processed through simulated telecommunication channels using real codec implementations. A listening test with 95 participants was conducted, involving binary classification (human vs. synthetic) and confidence ratings. Results show an overall detection accuracy of 54.8%, confirming that humans are poorly equipped to identify synthetic speech. Surprisingly, the highest accuracy was achieved for the narrowband GSM channel (63.7%), while VoLTE yielded the lowest performance (44.0%). The findings suggest that restricted bandwidth may emphasize prosodic irregularities typical of generative models, whereas high-quality channels mask synthetic artifacts, increasing susceptibility to voice spoofing. The results highlight the necessity of deploying additional security mechanisms in telecommunication systems relying on voice identity verification.
Percussion instruments exhibit complex vibrational behavior characterized by transient excitation, high modal density, and strong structural–acoustic coupling. Numerical modeling—especially the finite element method (FEM)—has become essential for analyzing realistic geometries, material heterogeneity, and fluid–structure interaction. This review systematically synthesizes FEM-based studies on percussion instruments, organized by their physical classification into idiophones and membranophones. The present work thematically compares modeling strategies and their trade-offs and highlights actionable research gaps. FEM and coupled FEM–boundary element (BEM) approaches applied to bars, plates, shells, membranes, and vibroacoustic systems are reviewed, with emphasis on modal behavior, tuning strategies, excitation mechanisms, nonlinear phenomena, and fluid–structure interaction. A key feature is the consistent validation of simulations against experimental measurements. The analysis reveals that while FEM is mature for modeling bars, plates, shells, and single-membrane systems, significant gaps remain: bar–resonator coupling and damping/residual stress modeling in idiophones, coupled clapper–bell–air simulations for bells, and fully coupled double-membrane simulations for drums. The latter directly affects predictions of modal frequencies, decay rates, and timbre. The review concludes by identifying priority research directions: fully coupled double-membrane models, material nonlinear viscoelasticity, efficient FEM–BEM coupling, and integration of performer-informed excitation for sound synthesis.
The acoustics and soundscapes of historical religious places (HRPs) have been investigated in the literature. Some of these places are still used for their original functions and for tourism purposes. Being susceptible to alterations and renovations that directly affect the auditory environment, assessing users’ perceptions under these changes becomes important. To clarify users’ experience in HRPs, this study conducted a systematic review by following the PRISMA guidelines. Two phases of literature review were followed. The first phase focused on acoustics-related studies. The results indicated that they address the physical and architectural acoustics of HRPs without including perceptual or experiential assessment. This led to the second phase which used perceptual and soundscape-related keywords. The results showed that there were 24 studies that included subjective evaluation and perceptual descriptors. Based on these results, perceptual attributes (indicators) and assessment scopes were thematically synthesized. The findings revealed a significant gap in linking objective acoustics conditions with subjective experience in HRPs, calling for an integration of both approaches in future studies.
Dust accumulation on photovoltaic (PV) modules reduces power generation efficiency, and traditional water-based cleaning is impractical in arid regions. Inspired by the classical acoustic phenomenon of Chladni figures-specifically the mechanism where an acoustic standing wave field drives the regular migration and accumulation of particles-this study proposes a waterless dust removal method using low-frequency ultrasonic vibration via piezoelectric excitation. Impedance analysis identifies optimal electromechanical coupling at 28 kHz. Experiments demonstrate that higher driving voltages accelerate cleaning, with recovery rates saturating beyond 125 V. Notably, intense friction and collisions between particles within high-density dust layers consume substantial kinetic energy, significantly multiplying the required cleaning time. Macroscopic transport analysis reveals that dust removal relies on the synergy of vibration-induced adhesion decoupling and gravity-driven transport. Sufficient tangential gravity is crucial for macroscopic particle removal, and tilt angles above 30 degrees provide the necessary downward driving force to ensure smooth particle sliding. Under optimal conditions, the system achieves an over 97% short-circuit current recovery at a low power consumption of similar to 10 W, providing a theoretical basis for waterless PV self-cleaning systems.
Prestressed steel strands transfer structural loads through complex anchorage systems. During through-anchorage ultrasonic guided-wave inspection, strong reflections generated in the anchorage segment may obscure defect-related echoes and create blind zones in the received signals. This study investigates the generation mechanisms of these anchorage-induced reflections and evaluates the relative roles of stress-induced acoustoelastic impedance variation and load-dependent interfacial contact evolution. An acoustoelastic finite element model is first used to estimate the reflection contribution caused by stress concentration alone. The results show that the stress-induced reflection remains weak, with the reflection coefficient remaining below 0.0125 even at 80% of the ultimate tensile strength. A sensitivity-based equivalent spring-contact model is then employed to examine whether effective strand-wedge and wedge-anchorage interfacial stiffness variations can generate anchorage reflections with comparable order of magnitude and load-dependent trends. The contact-based model produces much stronger reflections, and roughness-sensitivity analysis indicates that the load-dependent trend is not governed by a single nominal roughness assumption. Multi-specimen stepwise tensioning experiments show repeatable load-dependent reflection trends at both 80 kHz and 240 kHz. The results therefore suggest that, within the investigated geometry and loading range, interfacial contact evolution is a more plausible dominant contributor to anchorage-induced guided-wave reflections than stress-induced acoustoelastic impedance variation. This work focuses on the physical origin of anchorage reflections and provides a mechanistic basis for interpreting anchorage-induced interference in future through-anchorage defect detection.
This study focuses on how mesoscale eddies at the Kuroshio boundary in the East China Sea modulate underwater acoustic propagation. Using high-resolution reanalysis data from the Hybrid Coordinate Ocean Model (HYCOM) and validated acoustic ray-tracing simulations, the OW + SLA method is employed for eddy identification and classification. Statistical analysis of 120 eddy events from 2015 to 2020 clarifies their seasonal variation characteristics. Warm eddies shift the convergence zone 15-30 km away from the sound source and broaden it by 20-40%, while cold eddies shift it 10-25 km toward the source and narrow it by 15-35%. A linear relationship exists between eddy amplitude and acoustic transmission loss (TL = 72.4 + 0.42 h, R2 = 0.61), where TL is the transmission loss in decibels (dB) and h is the eddy amplitude in meters (m), and there are depth-dependent transmission loss modulation effects. These results provide practical guidance not only for sonar system design and acoustic communication optimization but also for error correction in underwater acoustic navigation systems operating in eddy-prone environments.
