Search Results (888)

The transition toward circular economy practices and CO₂ reduction goals is driving the development of new sound absorption technologies. Traditional absorbers made from mineral wool or foams provide broadband absorption; however, their production is associated with intensive energy consumption and non-renewable resources. This is why the focus has been shifting from the mere substitution of materials to integrated solutions that combine sustainability with structure. This paper reviews recent innovations in sustainable absorbers based on bio-based and recycled materials. The acoustic performance of porous materials depends on such factors such as pore structure, airflow resistivity and geometric parameters such as thickness, multi-layer structure and resonances. At the same time, additive manufacturing (AM) allows creating geometry-controlled absorbers providing advanced acoustic properties. Despite many sustainable absorbers demonstrating sufficient sound absorption properties at medium and high frequencies, their use at low frequencies remains challenging. Additionally, concerns regarding durability, flame retardance, and environmental consistency continue to limit their broader application. Yet, hybrid, multi-material strategies, particularly those combining geopolymer matrices with bio-based or recycled fillers, are identified as a promising route to address these limitations. This review outlines current trends and highlights key challenges and future directions in the design of sustainable sound-absorbing systems. Full article

Laser-induced acoustic communication is a highly adaptable cross-medium technique that combines the advantages of optical transmission through air and acoustic transmission underwater. However, poor signal stability at high repetition frequencies currently hinders its widespread application. To address this, this paper proposes an innovative scanning focal-point method to enhance stability. Traditional methods such as beam scanning, focus control, and distributed interaction are primarily aimed at enhancing sound pressure in a specific direction, achieving near-field/far-field focusing, or improving the signal-to-noise ratio through coherent synthesis of ultrasonic intensity. In contrast, the method proposed in this paper is intended to avoid the interference of droplets and vapor generated by single-point breakdown under high repetition frequencies, which would otherwise degrade the laser-acoustic conversion efficiency. It is therefore an active defense strategy specifically targeting the stability of laser-induced acoustic communication. First, optical simulation software was used to analyze the effects of surface ripples and bubbles on focal spot displacement and size. Next, a single-pulse experimental system was developed to measure the range and duration of surface depressions caused by optical breakdown. Finally, a scanning focal-point system was constructed for comparative experiments, with results recorded via hydrophones and high-speed cameras. The maximum laser-induced acoustic signal generated by the scanning focal-point method is 7.4 times that produced by single-point breakdown. The experimental results demonstrate that the scanning focal-point method can effectively avoid the influence of water surface disturbance and steam on the optoacoustic conversion efficiency and significantly improve the amplitude and stability of the laser-induced acoustic signal. Full article

Aiming at the technical bottleneck that traditional porous structures can hardly achieve mechanical load-bearing and acoustic regulation simultaneously, this study designs and fabricates three implicit surface porous structures (Gyroid, Diamond, Lidinoid) based on the bionic principle of trabecular bone. Experimental characterization and numerical analysis of their mechano-acoustic coupling performance are systematically carried out. Selective Laser Melting (SLM) technology is employed to realize the integrated forming of 316L bionic structures. Quasi-static compression experiments and finite element simulations are conducted to reveal the progressive deformation mechanism and energy absorption characteristics of different topological configurations. The results indicate that the Diamond structure exhibits the optimal comprehensive performance in terms of load-bearing capacity, specific energy absorption and isotropy. On this basis, the sound absorption and sound insulation performances of the structures are evaluated via an acoustic impedance tube test. The results show that the Diamond structure possesses a remarkably higher sound absorption coefficient and sound insulation value in the high-frequency range than other configurations, demonstrating excellent acoustic energy dissipation and sound wave isolation capability. The research indicates that the synergistic optimization of mechanical and acoustic performances can be achieved by regulating the Triply Periodic Minimal Surface (TPMS) topological configuration. Benefiting from its efficient stress transfer paths and intricate sound wave propagation channels, the Diamond structure realizes the coupling of high load-bearing capacity, superior energy absorption and favorable acoustic performance. This work provides a theoretical basis and technical support for the design of bionic porous structures in multifunctional scenarios such as bone implants and protective noise reduction. Full article

High sound pressure level (SPL) acoustic sensing requires miniaturized microphones that can operate under large acoustic loading while maintaining mechanical linearity, sufficient sensing response, and broadband audio frequency behavior. This work targets high-SPL operation and numerically investigates a graphene piezoresistive MEMS microphone based on a membrane-supported beam–island diaphragm. The proposed structure retains a continuous membrane for acoustic load bearing, while the upper beam–island topology redirects deformation-induced strain toward beam root regions where graphene piezoresistors are placed. This design is intended to increase the local strain available for piezoresistive readout without simply relying on larger global diaphragm deflection. Finite-element analysis was used to optimize the diaphragm geometry and evaluate strain enhancement, pressure response linearity, modal behavior, and harmonic response. Under the 170 dB SPL reference condition, the optimized structure increases the peak structural strain from 47.83 με in a thickness-equivalent solid diaphragm to 562.53 με, achieving an approximately 11.8-fold enhancement in local sensing strain while maintaining a highly linear pressure response (R2 > 0.9999). Additionally, the results also show that the sensor exhibits a high first natural frequency of 64.07 kHz and a small response variation of approximately 0.94 dB within the 0–20 kHz target frequency range, indicating excellent dynamic stability and high-fidelity signal transduction characteristics. To connect the structural response with piezoresistive readout, first-order electromechanical output estimation was further performed using representative graphene gauge factors, quarter-bridge readout assumptions, contact resistance correction, and Johnson-noise-limited signal-to-noise ratio estimation. A ±5% geometric tolerance check further indicates that the membrane side length is the most fabrication-sensitive parameter, while the selected design remains generally robust except for reduced linearity margin under positive membrane side-length deviation. These results demonstrate the potential of the proposed graphene-based MEMS microphone for high-SPL broadband acoustic sensing applications in harsh and high-intensity acoustic environments. Full article

A broadband sound-absorbing structure that combines a nonwoven sheet with a back air space and a Helmholtz resonator is proposed. The incident surface of the nonwoven sheet with the back air space is divided into two areas, and a sound-absorbing tile with high sound absorption coefficients across a wide frequency range is created by incorporating a Helmholtz resonator at the end of one of the back air spaces. Theoretical and experimental analyses were performed. Sound absorption coefficients were measured using a two-microphone impedance measurement tube and the theoretical values were derived using the transfer matrix method. The results demonstrate that the proposed sound-absorbing structure exhibits high sound absorption coefficients across a wide frequency range for both experimental and theoretical values. The sound absorption coefficient of the proposed sound-absorbing tile is improved in the low-frequency range, and the dip in the high-frequency range is eliminated. The sound absorption curve of the proposed tile became broader compared with either the Helmholtz resonator alone or the nonwoven sheet with a back air space alone. Theoretical values closely match experimental trends; thus, it is possible to estimate the sound absorption coefficients of the proposed structure with sufficient accuracy for practical applications. Full article

Acoustic behavior, essential for communication and perception, is metabolically demanding. Studying the energy costs of echolocation helps us to understand animal energy allocation and provides key insights into the evolutionary constraints of acoustic signals. We examined the constant-frequency bat Rhinolophus nippon using a miniature electrocardiogram system and a custom servomotor that moved prey toward stationary bats. This setup allowed for synchronous recording of high-resolution electrocardiogram and echolocation calls from the search phase to the approach phase. During the search phase, bats emitted isolated echolocation pulses characterized by long pulse durations and inter-pulse intervals (IPIs), together with higher root mean square (RMS) amplitude, pulse energy, and peak amplitude. In the approach phase, call rate increased significantly (3.15-fold), and bats predominantly produced sonar sound groups. Meanwhile, pulse duration, IPIs, RMS amplitude, and pulse energy decreased to 65.23%, 25.82%, 78.50%, and 86.32% of the corresponding search-phase values, whereas peak amplitude increased to 110.99%, indicating that R. nippon can flexibly adjust the structure of its echolocation calls. However, despite the increased call rate (p < 0.05), neither heart rate nor metabolic rate differed between phases. This study provides direct physiological evidence for understanding energy expenditure in bat echolocation and offers a methodological reference for future research. Full article

Background/Objectives: Cross-border meteorological disaster medical rescue policies in the Guangdong–Hong Kong–Macao Greater Bay Area face challenges in coordination, completeness, and effectiveness. Existing policy systems lack systematic quantitative evaluation. This study aims to assess the current policy landscape and provide evidence-based recommendations for optimizing cross-border medical rescue policy supply and enhancing regional emergency coordination. Methods: We reviewed policy documents on cross-border meteorological disaster medical rescue issued from 2005 to 2025 and used a combination of text mining and the PMC index model to quantitatively analyze and evaluate selected policy texts. The PMC scoring criteria (0–10 scale) define scores ≥ 7 as “excellent” and 5–6.99 as “good”. Results: Policy word frequency analysis showed that “emergency,” “disaster,” “meteorology,” and “management,” were core high-frequency words; semantic network clustering revealed five major thematic modules: monitoring and early warning, emergency rescue, medical treatment, material support, cross-border coordination. The PMC indices of the 26 policies ranged from 5.65 to 9.42, with an average score of 6.95, which corresponds to the “good” level. Policy 14 scored 9.42, reaching the “perfect” level; eight policies received an “excellent” rating, indicating generally high policy quality. From a dimensional perspective, X9 (policy evaluation), X1 (Nature of policy), and X8 (policy guarantee) scored relatively high, while X4 (policy type) and X2 (policy timeliness) scored relatively low. Conclusions: The overall performance of the cross-border meteorological disaster medical rescue policy system is good, with relatively sound policy transparency and institutional guarantees. However, the policy system has the following shortcomings: insufficient cross-border coordination mechanisms, shallow integration of medical rescue professional content into comprehensive policies, and an emphasis on short-term emergency response with inadequate medium- and long-term strategic planning. It is recommended to strengthen medium- and long-term top-level strategic planning, enhance the functional allocation of health departments in meteorological disaster emergency plans, and establish a cross-regional joint policy evaluation and dynamic revision mechanism. Full article

Shallow lunar subsurface characterization is a key requirement for future exploration activities, particularly for in situ resource utilization and the identification of protected environments for human and robotic operations. This work presents the preliminary design and performance assessment of an orbital very high frequency (VHF) radar sounder tailored to the detection of subsurface water ice deposits and lava tubes at depths relevant to exploration. The analysis combines physically based modeling of acquisition geometry, electromagnetic properties, and surface roughness with quantitative evaluation of signal-to-noise and signal-to-clutter ratios. Results indicate that surface clutter constitutes the primary limitation for subsurface detectability in orbital sounding, thereby driving both instrument design and mission geometry. Quantitative performance bounds are derived for penetration depth and spatial resolution, providing guidance for identifying regions where subsurface access may be achieved with reduced operational risk. One-dimensional electromagnetic simulations further demonstrate the advantages of operating in the VHF regime. While lower-frequency systems retain sensitivity to some subsurface interfaces, their limited vertical resolution prevents reliable separation of closely spaced structures, such as the roof and floor of lava tubes. In contrast, the proposed VHF sounder enables clear separation of multiple subsurface interfaces, allowing geometric characterization of cavities and improved discrimination of ice-bearing layers. These results establish the feasibility and relevance of a VHF orbital radar sounder as a dedicated tool for shallow lunar subsurface investigations in support of future exploration missions. Full article

Sound Event Localization and Detection (SELD) integrates Sound Event Detection (SED) and Direction-of-Arrival Estimation (DOAE) to recognize and localize sound events in various applications, including urban sound sensing, wildlife monitoring, and home surveillance. Recently, advancements in machine learning, particularly deep learning techniques, have demonstrated remarkable success in improving SELD performance. However, training deep learning models for SELD is challenged by the limited availability of high-quality spatial audio data, which is essential for accurate model generalization. This paper explores the effectiveness of data augmentation techniques in overcoming this limitation. We evaluate the impact of Frequency Shift (FS), Random Cutout (RC), and Channel Swapping (CS) on SELD performance using a comprehensive set of experiments. Our findings indicate that all tested augmentation combinations except FS alone significantly improve SELD performance, reducing the SELD error by approximately 8% compared to no augmentation. The differences among effective combinations are not statistically significant, suggesting that the decision to augment is more impactful than the specific combination chosen. This work highlights the critical role of data augmentation in enhancing SELD systems and suggests future research directions, including testing these techniques with different model architectures and exploring additional augmentation methods. Full article

The use of sound absorption materials has traditionally been restricted to medium-to-high frequencies due to their limitations at low frequencies, where the large wavelength of sound waves imposes rather bulky solutions. However, recent materials and designs allow for the absorption of sound waves with more practical sizes and weights, reviving interest in this frequency range. Some of these low-frequency absorbers, also named acoustic metamaterials or sub-wavelength sound absorbers, based on microperforated panels, are reviewed in this article. These include multilayer and multicavity microperforated panels, hybrid passive–active absorbers, multiple Helmholtz resonators, and microperforated panels with labyrinthine cavities or sonic black holes. Full article

This study systematically investigates the influence of sound waves on the flame morphology of oil pan fires in commercial kitchen fire scenarios through a combined approach of numerical simulation and experimental research. A two-dimensional numerical model was established using COMSOL Multiphysics to simulate the interaction mechanisms with flames under various sound source configurations, frequencies, and sound pressure levels. An experimental platform was then constructed to validate and refine the findings using flame morphology, center temperature, and combustion duration as metrics. Results confirm that sound waves effectively destabilize flames, with suppression effects exhibiting a nonlinear trend of initial enhancement followed by attenuation as frequency increases. At the optimal frequency, increasing sound pressure level significantly enhances suppression but exhibits saturation characteristics. Bilateral oblique sound sources simultaneously act on both sides of the flame root, synchronously thinning the boundary layer to create uniform suppression. This configuration also compensates for deflection effects at high frequencies in single-field scenarios, yielding higher efficiency. The determined optimal parameter combination is 1800 Hz and 50 dB, with bilateral oblique arrangement preferred. Full article

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. Full article

This study presents a comprehensive experimental investigation of lightweight cementitious composites incorporating pumice and expanded perlite as sustainable substitutes for conventional aggregate systems. Four replacement ratios (25%, 50%, 75%, and 100%) were evaluated to determine their effects on density, compressive strength, flexural strength, modulus of elasticity, and acoustic insulation properties, including the noise reduction coefficient (NRC) and frequency-dependent sound transmission loss (STL). The results showed that increasing the lightweight aggregate content generally reduced the strength-related mechanical properties while improving acoustic performance, particularly in the mid- and high-frequency ranges. Among all mixtures, the expanded perlite-based PRC-1.0 specimen exhibited the best overall acoustic performance, achieving the highest NRC value and the widest STL range. These findings demonstrate a clear trade-off between mechanical strength and acoustic efficiency, indicating that expanded perlite-based lightweight cementitious composites are promising materials for building applications requiring enhanced sound insulation performance. Full article

Presbycusis, or age-related hearing loss (ARHL), is a multifactorial disorder characterized by a gradual, bilateral sensorineural decline in hearing sensitivity, predominantly affecting high-frequency sounds. It is one of the most common chronic conditions in the aging population and represents a major public health concern due to its high prevalence and progressive nature. Presbycusis significantly impairs speech perception, especially in noisy environments, leading to communication difficulties, reduced social participation, increased risk of social isolation, and a decline in quality of life. Moreover, growing evidence highlights a strong association between ARHL and cognitive impairment, dementia, depression, and increased frailty in older adults. The etiology of presbycusis is complex and involves the interplay between genetic predisposition and cumulative environmental and lifestyle-related factors. Genetic susceptibility influences cochlear aging, neural degeneration, and vulnerability to external insults. Non-genetic contributors include chronic noise exposure, cardiovascular and metabolic disorders such as diabetes and dyslipidemia, ototoxic medications, smoking, and other lifestyle factors that may accelerate cochlear damage through oxidative stress and microvascular dysfunction. This narrative review aims to provide an updated overview of the genetic and environmental determinants involved in the development and progression of presbycusis. Furthermore, it discusses the clinical implications of these factors for early identification, audiological evaluation, prevention strategies, and personalized management approaches. A better understanding of the multifactorial nature of presbycusis may support the development of targeted interventions to preserve hearing function and improve overall health outcomes in the aging population. Full article

To balance load-bearing capacity and acoustic insulation, this study proposes a sandwich reinforced concrete (RC) slab with W-shaped interlayer inclined rebar connectors and investigates their influence on acoustic bridging. A three-dimensional vibro-acoustic finite element modeling approach was adapted to analyze airborne sound insulation and impact sound pressure levels in the frequency domain and was validated against experimental results. Parametric analyses were then conducted to evaluate the effects of connector number, connector geometry, anchorage-end treatment, and core-layer parameters. The results revealed distinct frequency-dependent behavior. The introduction of connectors produced a stable dip in airborne sound insulation near 400 Hz and a pronounced impact-sound peak within 200–400 Hz, both associated with connector-controlled coupled characteristic frequencies. Increasing the number of connectors strengthened interlayer stiffness coupling and intensified acoustic bridging in these frequency ranges. By contrast, optimizing the connector structure or introducing a compliant end layer reduced coupling and improved acoustic insulation. Overall, acoustic performance can be improved by reducing the equivalent coupling stiffness of the connectors, enhancing energy dissipation at the connector ends, and appropriately selecting the core-layer parameters. These measures help suppress the characteristic-frequency response and improve mid- to high-frequency sound insulation. Full article