Sound Transmission Research Articles

A semi-analytical method using auxiliary sine series for vibration and sound radiation of a rectangular plate with elastic edges

This paper proposes an efficient semi-analytical method using auxiliary sine series for transverse vibration and sound radiation of a thin rectangular plate with edges elastically restrained against translation and rotation. The formulation, constructed by two-dimensional sine and/or cosine series, can approximately express the bending displacement, and calculate vibration and sound radiation under excitation of point force, arbitrary-angle plane wave, or diffuse acoustic field with acceptable accuracy. It is also applied for baffled or unbaffled conditions. A post-process program is developed to predict vibrating frequencies and modes, mean square velocity spectrum, and sound transmission loss via reduced-order integrals of radiation impedances. The method is validated by experiment and simulation results, demonstrating accurate and efficient computation using a single program for transverse vibration and sound radiation of a plate under different elastic boundary conditions and different excitations. Formulas given in this paper provide a basis for the code development on transverse vibration and sound radiation analysis of thin plates.

Potential of acoustic sensors for real-time monitoring of physicochemical properties of milk protein concentrate during ultrafiltration

Ultrafiltration (UF) is the step for concentrating protein in milk and whey prior to evaporation and drying in dairy ingredient production, e.g. milk protein concentrate (MPC). To optimize UF process, it is important to monitor changes in product/process parameters. Two in-line sensors with outputs: 1. bulk acoustic wave (BAW), acoustic viscosity (AV); 2. surface acoustic wave (SAW), acoustic impedance (AI) and acoustic transmission (AT), were evaluated to measure MPC physicochemical properties (total solids (TS), density, protein and apparent viscosity) during UF. Trials were quintuplicated in a UF membrane pilot-plant, to concentrate feed (TS 11.36–19.10%). Models for predicting MPC physicochemical properties developed by acoustic parameters performed well, especially by AI and AT, with R2 > 0.963, SEP <1.076 to predict apparent viscosity, and R2 > 0.980, SEP <0.627 for all other properties’ prediction. This study demonstrated the potential of both acoustic sensors for UF process monitoring.

Skeleton Integral Equations for Acoustic Transmission Problems with Varying Coefficients

Skeleton Integral Equations for Acoustic Transmission Problems with Varying Coefficients

The Impact of Special Marine Environments Such as the Kuroshio on Hydroacoustic Detection Equipment

In order to study the impact of acoustic propagation characteristics in the northeastern South China Sea, GEBCO08 global terrain grid data and Argo data were used to numerically simulate the acoustic transmission characteristics of two stations in the northeast South China Sea affected by the Kuroshio. The impact of different marine environments on acoustic transmission characteristics was analyzed. The results show that increasing the deployment depth of a sound source within a certain range will reduce the transmission loss; deploying a sound source near the axis of the surface acoustic channel or the deep-sea acoustic channel will also greatly increase the propagation distance of sound signals; and the presence of topography such as undersea mountains will increase the transmission loss.

Prescribed fire and natural habitat characteristics affect crawfish frog (Rana areolata) advertisement call transmission

ABSTRACT For acoustically signalling animals, the rate of signal degradation is critical for successful communication. Degradation is heavily influenced by habitat characteristics, with sound degrading more rapidly in the presence of environmental obstacles (e.g. vegetation). Land management strategies such as prescribed burns eliminate obstacles and should therefore lead to more efficient sound transmission. Crawfish frogs (Rana areolata) produce long-distance advertisement calls for breeding. Habitats surrounding crawfish frog breeding ponds vary in vegetative density, and prairies surrounding breeding habitat often undergo controlled burns prior to the breeding season. We hypothesised that R. areolata advertisement calls would transmit more efficiently in post-burned prairies compared to other more vegetated habitats. To test this hypothesis, we conducted a sound transmission playback experiment, broadcasting crawfish frog calls in three habitats: forest, prairie, and post-burned prairie. We compared sound degradation measures between habitat types and across distances. We found that crawfish frog calls experienced up to 6.8 dB less excess attenuation in post-burned habitats relative to other habitat types, and that in general, prairie habitats had better sound transmission than forest. These results indicate that land management and habitat structure have consequences for acoustic communication, and may also influence the findings of frog call detection surveys.

Acoustic wave propagation in depth-evolving sound-speed field using the lattice Boltzmann method

This study investigates the propagation of sound waves within deep-sea low-sound-speed channels using the lattice Boltzmann method, with a key focus on the influence of depth-dependent sound speed on wave propagation. The depth-variable sound speed condition is realized through the incorporation of an external force proportional to the density gradient. After the model verification, investigations into the two-dimensional spreading of sound sources reveal that the depth-dependent sound speed curves the wave propagation. When source depths differing from the low-sound-speed channel, wave paths deviate due to contrasting speeds above and below. When the sound source is situated within the low-sound-speed channel, waves exhibit converging patterns. The simulations also detail the total reflection behavior of sound waves. When the incident angle falls exceeds the critical angle, the waves remain intact within the low-sound-speed channel, thereby enabling the preservation of high amplitude acoustic signals even at remote locations. The subsequent simulations of sound wave propagation around obstacles demonstrate that the low-sound-speed channel also exhibits better signal transmission capabilities in the presence of obstacles. In a uniform sound speed environment, acoustic wave propagation around a submarine exhibits a symmetric pattern. By contrast, under depth-evolving speed conditions, submarines operating at various depths manifest distinct propagation characteristics, such as asymmetric wave propagation during shallow diving, as well as wave attenuation or even silencing when cruising within low-sound-speed channels. These findings underscore the profound implications of depth-evolving sound speed on underwater acoustic signal detection and transmission.

Experimental Investigation on the Acoustic Insulation Properties of Filled Paper Honeycomb-Core Wallboards.

Honeycomb plates, due to their multi-cavity structure, exhibit excellent mechanical properties and sound insulation. Previous studies have demonstrated that altering the cell size and arrangement of honeycomb structures impacts their acoustic performance. Based on these findings, this study developed a wallboard structure with enhanced sound insulation by filling the cavities with paper fiber/cement facesheets and designing a stacked core structure. Through the reverberation chamber-anechoic chamber sound insulation experiment under 100-6300 Hz excitation and conducting orthogonal experiments from three dimensions, it was found that: (1) Compared to no filling, the filling with straw and glazed hollow bead can increase the sound transmission loss (STL) by more than 50% in the frequency bandwidth above 2000 Hz. This indicates that both types of fillings can significantly enhance the sound insulation performance of the honeycomb structure without a significant increase in economic costs. (2) The increase in paper fiber/cement facesheets improves the STL across the entire experimental bandwidth, with a maximum improvement exceeding 70%. This structural design not only offers superior sound insulation performance but also better suits practical engineering applications. (3) Increasing the number of core stacking units (from one to three), taking straw-filled paper honeycomb-core wallboards as an example, effectively increased the STL bandwidth. (4) This test enriches the application of honeycomb plates in sound insulation. Introducing fiber paper fiber/cement facesheets and eco-friendly, low-cost straw improves sound insulation and enhances the strength of honeycomb, making them more suitable for construction, particularly as non-load-bearing structures.

Investigation of the Variation in Insertion Loss of Vertical Noise Barriers for High-speed Railways at Different Levels of Sound Transmission Loss

Abstract The present study investigates the impact of sound transmission loss of vertical noise barriers for high-speed railways on insertion loss at various speed grades and heights. The findings reveal an initial increase in insertion loss followed by a plateau as sound transmission loss improves. A threshold value exists for weighted sound transmission loss, beyond which the insertion loss remains relatively constant. This threshold referred to as the minimum weighted sound transmission loss decreases with increasing train speeds and increases with higher noise barrier heights. The variation in insertion loss was calculated for noise barriers at heights of 2m and 3m under different sound transmission loss conditions, using measured sound source data corresponding to train speeds of 150km/h, 200km/h, 250km/h, 300km/h, and 350km/h. By polynomial fitting, at a train speed of 400 km/h, the minimum weighted sound transmission loss for 2m and 3m high noise barriers are determined to be 20dB and 21dB respectively.

Topology optimization design of multi-modal resonators for metamaterial panels with maximized broadband vibroacoustic attenuation

Resonant metamaterial panels can achieve exceptional vibroacoustic attenuation by subwavelength local resonators attached to a host structure. While single-mode resonators provide improvements only in a narrow band, recent advancements propose multi-modal resonators for broadband attenuation. However, existing designs utilize only a limited number of modes, and effective methodologies are lacking to systematically design resonator layouts that achieve an appropriate amount of resonances across the target frequency range, with an adequate participating mass. In this study, we tackle this challenge by developing a dedicated topology optimization method for multi-modal resonator design in metamaterial panels. The method leverages effective thin plate modelling, i.e. a homogenized metamaterial representation through an effective mass density, which provides accurate and very efficient vibroacoustic predictions. The optimization objective is to maximize the broadband diffuse field sound transmission loss (STL) of the metamaterial panel while constraining mass. The optimization problem is solved by gradient-based mathematical programming, for which the necessary (adjoint) sensitivities of objective and constraints are derived. The efficacy of the proposed topology optimization approach is demonstrated by targeting the suppression of coincidence dips in orthotropic host plates. For narrowband coincidence dips, the optimized resonator exhibits maximized mass participation in one single mode of interest. For broadband coincidence dips, the method effectively generates multi-modal resonators with up to 6 resonances distributed across the target frequency range. It is finally demonstrated that the topology-optimized designs surpass the performance of simpler, parametrically optimized multi-modal resonator layouts, as well as of conventional treatments by a damping layer of rubber.

FOXO1-NCOA4 Axis Contributes to Cisplatin-Induced Cochlea Spiral Ganglion Neuron Ferroptosis via Ferritinophagy.

Mammalian cochlea spiral ganglion neurons (SGNs) are crucial for sound transmission, they can be damaged by chemotherapy drug cisplatin and lead to irreversible sensorineural hearing loss (SNHL), while such damage can also render cochlear implants ineffective. However, the mechanisms underlying cisplatin-induced SGNs damage and subsequent SNHL are still under debate and there is no currently effective clinical treatment. Here, this study demonstrates that ferroptosis is triggered in SGNs following exposure to cisplatin. Inhibiting ferroptosis protects against cisplatin-induced SGNs damage and hearing loss, while inducing ferroptosis intensifies these effects. Furthermore, cisplatin prompts nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy in SGNs, while knocking down NCOA4 mitigates cisplatin-induced ferroptosis and hearing loss. Notably, the upstream regulator of NCOA4 is identified and transcription factor forkhead box O1 (FOXO1) is shown to directly suppress NCOA4 expression in SGNs. The knocking down of FOXO1 amplifies NCOA4-mediated ferritinophagy, increases ferroptosis and lipid peroxidation, while disrupting the interaction between FOXO1 and NCOA4 in NCOA4 knock out mice prevents the cisplatin-induced SGN ferroptosis and hearing loss. Collectively, this study highlights the critical role of the FOXO1-NCOA4 axis in regulating ferritinophagy and ferroptosis in cisplatin-induced SGNs damage, offering promising therapeutic targets for SNHL mitigation.

Ontogeny of the malleus in Mesocricetus auratus (Mammalia, Rodentia): Systematic and functional implications for the muroid middle ear.

The three mammalian auditory ossicles enhance sound transmission from the tympanic membrane to the inner ear. The anterior anchoring of the malleus is one of the key characters for functional classification of the auditory ossicles. Previous studies revealed a medial outgrowth of the mallear anterior process, the processus internus praearticularis, which serves as an anchor for the auditory ossicle chain but has been often missed due to its delicate nature. Here we describe the development and morphology of the malleus and its processus internus praearticularis in the cricetine rodent Mesocricetus auratus, compared to selected muroid species (Cricetus cricetus, Peromyscus maniculatus, and Mus musculus). Early postnatal stages of Mesocricetus show the formation of the malleus by fusion of the prearticular and mallear main body. The processus internus praearticularis forms an increasing broad lamina fused anteriorly to the ectotympanic in adult stages of all studied species. Peromyscus and Mus show a distinct orbicular apophysis that increases inertia of the malleus and therefore these species represent the microtype of auditory ossicles. In contrast, the center of mass of the malleus in the studied Cricetinae is close to the anatomical axis of rotation and their auditory ossicles represent the transitional type. The microtype belongs to the grundplan of Muroidea and is plesiomorphic for Cricetidae, whereas the transitional type evolved several times within Muroidea and represents an apomorphic feature of Cricetinae.

Adjustable stereo path design method based on pin-sculpture acoustic topological insulator with Z-dislocation defect immunity

The field of topological protected wave engineering, inspired by quantum mechanics, has generated significant interest. Acoustic analogs of electronic topological insulators provide new opportunities for manipulating sound propagation with unconventional acoustic edge modes that are immune to backscattering. Numerous reports have been published on the design of two-dimensional acoustic topological insulators (ATIs). However, the sound path of a two-dimensional design is simple, and its ability to control sound waves is limited. On the other hand, the design of 3D ATIs is relatively complex, making it difficult to manufacture and limiting its versatility. Based on the design idea of the 2D ATIs, inspired by the art named 3D pin-sculpture, an adjustable structure of a finite size consisting of spindle-shaped units with a variable cross section is designed to realize flexible path transformation. Furthermore, unlike two-dimensional structural defects, such as cavities and disorder, the analysis of vertical dislocation defects in finite-sized structures allows for the design of local sound propagation along the z-direction, providing a concept for constructing a stereo path. The designed structure also serves two functions: acoustic switch and delay. This idea offers an alternative approach to designing complex sound transmission paths.

Acoustic Transmission Measurements for Extracting the Mechanical Properties of Complex 3D MEMS Transducers.

Recent publications on acoustic MEMS transducers present a new three-dimensional folded diaphragm that utilizes buried in-plane vibrating structures to increase the active area from a small chip volume. Characterization of the mechanical properties plays a key role in the development of new MEMS transducers, whereby established measurement methods are usually tailored to structures close to the sample surface. In order to access the lateral vibrations, extensive and destructive sample preparation is required. This work presents a new passive measurement technique that combines acoustic transmission measurements and lumped-element modelling. For diaphragms of different lengths, compliances between 0.08 × 10-15 and 1.04 × 10-15 m3/Pa are determined without using destructive or complex preparations. In particular, for lengths above 1000 µm, the results differ from numerical simulations by only 4% or less.

Sound transmission of truss-based X-shaped inertial amplification metamaterial double panels

To enhance the low-frequency sound insulation performance of conventional double panels, this work proposes a truss-based X-shape inertial amplification (TXIA) metamaterial double panel. A semi-analytical method is developed for computing the sound transmission loss (STL) of the TXIA metamaterial double panel, with numerical and experimental validations confirming the convergence and accuracy of this method. To further investigate the low-frequency acoustic wave attenuation of the proposed structure, four configurations are analyzed and discussed. Numerical results indicate that, compared to conventional and equivalent mass double panels, the TXIA metamaterial double panel effectively shifts the STL peaks to lower frequencies, exhibiting higher STL amplitudes and a reduced low-STL region. Configurations incorporating different springs enhance the STL performance without altering mass or other parameters. The STL dips of the metamaterial double panel coincide with odd-odd modes of the double panel, which have higher radiation efficiencies. Parametric studies reveal that changes in the IA angle shift the dips induced by in-phase modes to lower frequencies, while increased stiffness shifts these in-phase dips to higher frequencies. The depth of the cavity between the two panels only affects the first-order anti-phase dip. Additionally, increased stiffness enhances the STL performance and introduces a new peak in the stiffness-controlled region. Due to its flexibility, the TXIA metamaterial double panel holds significant potential for industrial applications.

A two‐layered, analytically‐tractable, atmospheric model applied to Earth, Mars, and Titan with sources

AbstractThis work utilizes an analytic expression for a model of acoustic propagation in a two‐layered, inhomogeneous atmosphere developed by the authors. The model is used to study the atmospheres of Earth, Mars, and Titan. In particular, vertical wave propagation in these atmospheres is studied. The effect(s) of a two‐layered, inhomogeneous atmosphere on vertical, acoustic propagation due to a time‐harmonic, point source are examined. An adiabatic atmosphere is used for the bottom layer (troposphere) and an isothermal one for the top (stratosphere). The derived, analytic solution is expressed in terms of the acoustic pressure fluctuations. For the adiabatic layers, the solutions satisfy Bessel's equation for orders of , and for Earth, Mars, and Titan, respectively. The Bessel function's argument is , where and are dimensionless frequency and height, respectively. For the isothermal layer, the solution represents a damped, harmonic oscillator with a cutoff value of . Only values greater than are considered. The analysis and results are reported for combinations of single‐ and double‐layer atmospheres in the presence of a source on given boundaries. Acoustic propagation and transmission loss results are shown and discussed for all three planetary bodies: Earth, Mars, and Titan.

Electrospun Polyvinylidene Fluoride Membranes: Waterproofing and Acoustic Performance for Air and Acoustic Vents in Electronics.

Advancements in electronic devices demand materials capable of exceptional performance in various challenging environments. This study presents polyvinylidene fluoride (PVDF) nonwoven membranes with controlled porosity, created using an air-guided electrospinning method, followed by a calendaring process. These membranes exhibit a combination of water-repellent properties and sound transmission capabilities, making them ideal candidates for use in air and acoustic vents in electronic systems. A key feature of our membrane is the three-dimensional nanostructured pores, ranging from 0.20 to 0.76 μm, with a mean pore size of 0.51 μm, achieved through the formation of randomly arranged long nanofibers. By employing both experimental and theoretical methods, we achieved impressive performance metrics: air permeability of 0.86 cm3/cm2/s, water contact angles up to 139.3°, and breakthrough pressure as low as 0.27 MPa. Our PVDF nonwoven membranes maintain an optimal balance of stiffness, density, and air permeability, leading to exceptionally low sound transmission loss values ranging between -10 and -40 dBV/Pa, all while preserving their structural integrity. These findings contribute to the development of next-generation waterproof and acoustically permeable membranes, offering enhanced performance capabilities in demanding operational scenarios. This work advances the field of nanomaterials, environmental engineering, and acoustic technologies, with the potential to influence the design of future electronic devices.

Electrospun graphene oxide/polymeric nanocomposites for eardrum replacements

The development of structures and devices with enhanced acousto-mechanical properties is a topic of interest in engineering, especially in the biomedical field. A case study is the reconstruction of the tympanic membrane after partial or complete damage, such as from chronic suppurative otitis media, which is the leading cause of infectious diseases in children. In this work, we developed graphene-oxide (GO) nanocomposite polymeric scaffolds fabricated via electrospinning to assess their potential suitability as substitutes of the eardrum. To evaluate the structural influence of GO on the fibrous mesh, we performed a characterization in terms of wettability, mechanical properties, and surface morphology. Moreover, a finite-element model of the middle ear was employed to assess the acousto-mechanical behavior of the eardrum upon application of the developed scaffolds. We observed that GO influenced the morphology of the fibrous scaffolds by increasing the mean diameter of the fibers, their stiffness and strength, while decreasing the water contact angle, thus making the structures more hydrophilic. From the acoustic standpoint, the simulations showed that GO does not significantly affect sound transmission, except for PVDF-based structures, for which GO slightly improves the behavior only up to 2 kHz, but with a suboptimal performance at higher frequencies. Our results open to the development of fibrous nanocomposite polymeric scaffolds with an enhanced acoustic behavior for structural applications not limited to bioengineering.

Soundbox-based sound insulation measurement of composite panels with viscoelastic damping

Sound transmission loss (STL), an essential index for assessing the sound insulation performance of composite laminated structures, typically relies on experimental methods to measure. The soundbox method (SBM), a straightforward technique for measuring the STL, is sensitive to microphones’ positions. Within the framework of the Chebyshev-Ritz method, a semi-analytical vibro-acoustic model extended to composite laminated panels with viscoelastic damping (VED) is proposed for the first time. Based on the developed simplified layer-wise theory, the panel is modeled using three layers: the top face layer, the VED layer, and the bottom face layer. A closed cavity is added to the model as the soundbox enclosure used in actual measurements. By employing the Hamilton's principle, the governing equation for the coupling system is derived, and the vibration and internal acoustic responses of the coupling system are calculated. A discretization strategy is introduced to address the frequency-dependent properties of the VED layer, avoiding the need to reconstruct the stiffness matrix at each frequency. To obtain the STL of the panel, sound pressures at external measurement points are calculated based on the Rayleigh integral. The proposed model is validated against numerical results from finite element analyses. The influences of the microphone position inside and outside the cavity on the measured STL are studied. Furthermore, parametric studies over the microphones' positions are performed to enhance the SBM-based evaluation of the composite panel's sound insulation performance. The optimal locations for two internal microphones and one external microphone are recommended. Finally, experimental studies are carried out to guide the implementation of the SBM.

Sound transmission loss and bending properties of sandwich structures based on triply periodic minimal surfaces

Four types of triply periodic minimal surfaces sandwich structures (TPMS-SS), namely, G-SS, D-SS, D1-SS, and IWP-SS, have been proposed. The bending properties were evaluated by experiments and numerical simulations, and their sound insulation performance was investigated using theoretical, numerical and experimental methods. Firstly, the bending performance of four TPMS-SS was compared. Then, the acoustic vibration control equation of TPMS-SS was established and the theoretical solution for the sound transmission loss (STL) was derived based on Reissner's theory combined with the fluid-solid coupling condition. Next, experimental study was conducted on the STL performance of TPMS-SS using the impedance tube method, and the numerical model was verified using theoretical and experimental results. Finally, parametric studies were carried out to investigate the effects of parameters such as relative density (RD), panel thickness (hf), and sound incidence elevation angle (φ), as well as the type of structure, on the STL performance. The results show that TPMS-SSs can achieve >30 dB of STL in the frequency range of 1 Hz to 10 kHz. The STL value increases with relative density (RD), panel thickness (hf), and sound incident elevation angle (φ), while the location of the dips in the STL curves is affected by relative density and panel thickness. G-SS has the best bending performance, while D1-SS has the best acoustic performance. The results could be used for the optimization design of lightweight sandwich structures.

Development of a Non-Structural Prefabricated Panel Based on Construction and Demolition Waste for Sustainable Construction

The study focuses on developing a prefabricated panel for non-structural purposes by optimizing mortar mix designs incorporating recycled microplastic (RMP) and construction demolition waste (CDW) at various ratios (0, 10, 20, 30, and 100%). Experimental procedures encompassed material characterization, mortar specimen manufacturing, compression resistance testing, and thermal/acoustic panel tests following Colombian technical standards. Results indicate that incorporating 20% CDW enhances material strength, with cylinder number 3 (20% of CDW) achieving a resistance of 31.45 MPa. Panels incorporating recyclable waste materials show improved acoustic and thermal insulation properties, with up to 39 dB reduction in sound transmission and a 21 °C decrease in thermal transmission observed (5.6% and 35% for panel and door, respectively). This research advances sustainable construction practices demonstrating the potential of prefabricated panels using recyclable materials, offering eco-friendly solutions with enhanced performance characteristics for construction applications.