Sound Energy Research Articles

The Critical Thing about the Ear's Sensory Hair Cells.

The capabilities of the human ear are remarkable. We can normally detect acoustic stimuli down to a threshold sound-pressure level of 0 dB (decibels) at the entrance to the external ear, which elicits eardrum vibrations in the picometer range. From this threshold up to the onset of pain, 120 dB, our ears can encompass sounds that differ in power by a trillionfold. The comprehension of speech and enjoyment of music result from our ability to distinguish between tones that differ in frequency by only 0.2%. All these capabilities vanish upon damage to the ear's receptors, the mechanoreceptive sensory hair cells. Each cochlea, the auditory organ of the inner ear, contains some 16,000 such cells that are frequency-tuned between ∼20 Hz (cycles per second) and 20,000 Hz. Remarkably enough, hair cells do not simply capture sound energy: they can also exhibit an active process whereby sound signals are amplified, tuned, and scaled. This article describes the active process in detail and offers evidence that its striking features emerge from the operation of hair cells on the brink of an oscillatory instability-one example of the critical phenomena that are widespread in physics.

A new wearable cardiac acoustic monitoring technology for the evaluation of subclinical leaflet thrombosis after transcatheter aortic valve replacement: a pilot study

Abstract Background Subclinical leaflet thrombosis characterized by hypoattenuated leaflet thickening (HALT) and reduced leaflet motion (RLM) is a common complication after transcatheter aortic valve replacement (TAVR), whether it affects hemodynamic change is still debated. Purpose We attempted to use a novel wearable heart acoustic monitoring device, and combined multi-dimensional computed tomography (MDCT) and echocardiography to diagnose SLT and analyze the changes of transvalvular hemodynamics after TAVR. Methods Patients with severe symptomatic aortic stenosis and underwent successful TAVR were consecutively enrolled. Clinical data, acoustic cardiographic parameters including the frequency, amplitude, and energy of heart sounds , and imaging results were collected and analyzed by Core laboratory at pre- and post TAVR, and follow-up at one month and six month. According to severity of SLT at one month follow-up, we divided the patients into three groups: Group1: no SLT, Group2: mild SLT, defined as existed HALT did not qualify for Group 3, and Group 3: moderate to severe SLT, defined as at least 1 leaflet with HALT of grade 3 or 4 or RLM of ≥50%, or 2 leaflets with HALT of grade 2 or RLM of ≥50%. A consistency analysis of SLT presence between MDCT findings and acoustic cardiographic variables was performed using Kappa statistics. Results The study included 116 TAVR patients. The prevalence of SLT as detected by MDCT at one-month follow-up was 25%, with moderate to severe SLT representing 11.2% of cases. A significant decrease in aortic valve orifice area (AVA) (-0.2±0.48cm2 vs. -0.1±0.33cm2, p=0.009) and an increase in mean gradient (MG) (3.5±5.85 mmHg vs. 0.1±11.34mmHg, p=0.028) were observed in moderate to severe SLT group at one-month follow-up versus post-TAVR via echocardiography. However, no significant differences were found in the mild SLT or no SLT group. Acoustic cardiographic characteristics exhibited a distinct pattern with early systolic, baseless, and high-energy murmurs in patients with moderate to severe SLT, but not in the mild SLT or no SLT group. The sensitivity, specificity, and Kappa values for acoustic cardiography in diagnosing moderate to severe SLT were 81.82%, 83.33%, and 0.41, respectively. At the 6-month follow-up, MDCT showed that 11 (85%) patients with moderate to severe SLT who received anticoagulant therapy reached complete dissolution of SLT. Conclusion Moderate to severe SLT presented notably transvalvular hemodynamic influences following TAVR. Acoustic cardiography demonstrated specific characteristics of moderate to severe SLT, providing a valuable tool for SLT diagnosis and evaluation in clinical follow-up.Figure 1.Baseline characteristicsFigure 2.SLT and acoustic cardiography

Model of superior semicircular canal dehiscence: asymmetrical vestibular dysfunction induces reversible balance impairment.

Superior semicircular canal dehiscence (SSCD) is a vestibular-cochlear disorder in humans in which a pathological third mobile window of the otic capsule creates changes to the flow of sound pressure energy through the perilymph/endolymph. The primary symptoms include sound-induced dizziness/vertigo, inner ear conductive hearing loss, autophony, headaches, and visual problems. We have developed an animal model of this human condition in the Mongolian Gerbil that uses surgically created SSCD to induce the condition. A feature that is unique in this model is that spontaneous resurfacing of the dehiscence occurs via osteoneogenesis without a subsequent intervention. In this study, we completed our assessment of this model to include reversible asymmetrical vestibular impairments that interfere with balance. Adult Mongolian gerbils (N = 6) were trained to complete a balance beam task. They were also trained to perform a Rotarod task. After 10 days of training, preoperative ABR and c+VEMP testing was followed by a surgical fenestration of the left superior semicircular canal. Balance beam testing recommenced at postoperative day 6 and continued through postoperative day 15 at which point final ABR and c+VEMP testing was carried out. Behavioral comparison of preoperative and postoperative performance show a significant decrease in Rotarod performance, increased rates of falling, and an increase in time to cross the balance beam. Impairments were the most significant at postoperative day 7 with a return toward preoperative performance by postoperative day 14. This behavioral impairment was correlated with residual impairments to auditory thresholds and vestibular myogenic amplitudes at postoperative day 14. These results confirm that aberrant asymmetric vestibular output in our model of SSCD results in reversible balance impairments. The level of these behavioral impairments is directly correlated with severity of the vestibular dysfunction as we have previously reported for peripheral ear physiology and cognition.

Facade Design and the Outdoor Acoustic Environment: A Case Study at Batna 1 University

The relationship between architectural design and outdoor acoustic environments remains underexplored, particularly in educational spaces where noise levels impact comfort and usability. This study investigates the impact of building facade height on the outdoor acoustic environment in university courtyards. Acoustic measurements were conducted in two courtyards at Batna 1 University, each surrounded by buildings with distinct facade heights. Key acoustic parameters, including reverberation time (RT), early decay time (EDT), rapid speech transmission index (RaSTI), Definition (D50), and sound pressure level (SPL) attenuation were evaluated at specified source-receiver distances. The results reveal a strong correlation between RT20 and distance at higher frequencies due to building facade reflections, while lower frequencies are more influenced by geometric configuration and material absorption properties. The results demonstrate that RT and EDT increase logarithmically or polynomially with distance, especially at higher frequencies (2000–4000 Hz), due to the decrease in direct sound energy and increase in reflected sound amplitude. Taller building facades lead to longer RT and EDT values compared to lower heights. D50 and RaSTI decrease polynomially with increasing source–receiver distance, with lower values observed in the courtyard with taller facades, indicating reduced speech clarity. The SPL attenuation is influenced by surrounding geometry, with the least reduction in the courtyard with lower facade heights, followed by the taller facade courtyard, contrasting with semi-free field conditions. These findings highlight the significant role of building facade height and architectural elements in shaping the acoustic characteristics of outdoor spaces, providing valuable insights for designing acoustically comfortable urban environments, particularly in educational settings.

Acoustic Analysis of the Masjid at Necmettin Erbakan University Köyceğiz Campus in Konya

In this study, the passive acoustic performance of Necmettin Erbakan University Köyceğiz Campus Masjid was investigated. Designed as the largest masjid of the city with a capacity of 15,000 people and a volume of 43,200 m3, the masjid, which has traces of Seljuk, Ottoman and Modern architecture. is built as a complex at a location overlooking the city in the Meram District of Konya City, Turkiye. The aim of the study is to determine the acoustic comfort conditions by considering all the activities in the masjids as a whole. Within the scope of the study, the acoustic performance of the masjid was evaluated by determining different source and receiver points for each mode of activity. As a method, the chosen masjid was simulated with ODEON Room Acoustics Software Ver. 14.04 software. Objective room acoustic parameters were analysed in three groups. These are sound energy ratio parameters (reverberation time (RT), early decay time (EDT), clarity (C50, C80), lateral fraction (LF80)), speech intelligibility parameters (definition (D50), speech transmission index (STI)) and sound strength parameters (strength (G)). The results obtained were compared with precedent studies in the literature. In comparison with the acoustic values obtained in other masjid/mosque buildings, it was reported that, while the speech intelligibility of other masjids/mosques was at a satisfactory level, the masjid under consideration was at a poor level in both fully occupied and unoccupied conditions. In the analysis made for reverberation time, it was seen that the masjid discussed in this study showed similar characteristics to other masjids/mosques globally. As a result, it was determined that the dimensions of the surfaces forming the mihrab, the minbar design and the depths of the mahfil overhangs are effective regarding the acoustics of the masjid, and the design of curved surfaces should be carried out in a way that does not cause focusing problems. In addition, suggestions that can give guidelines to modern masjid designs have been put forward.

Effect of void ratio and rubber particles on the noise reduction mechanism and comprehensive performance of porous elastic road surface

ABSTRACT Porous Elastic Road Surface (PERS) is recognised as a pavement with excellent noise reduction ability. However, the mechanisms and field test evaluations of noise reduction for PERS have been not sufficiently explored. This study aims to investigate the effect of void ratio and rubber particle content on the noise reduction of PERS. PERS mixtures were prepared with varying void ratios and rubber particle contents, and subsequently tested by acoustic performance tests. The results reveal a decrease in sound pressure level, noise energy and dynamic modulus with increasing void ratio or rubber particle content. Conversely, the sound absorption coefficient presents an inverse relationship. The presence of interconnected voids significantly influences the noise reduction ability of PERS. However, excessive rubber particles can lead to decreased sound absorption coefficient. Furthermore, an optimised composition of PERS balancing road performance and noise reduction is identified. It is concluded that a PERS mixture featured with 25% void ratio, 4.5% polyurethane content and 20% rubber particle content exhibits good road performance and noise reduction ability. Notably, field tests indicate the sound pressure level reduce 9.1 dB(A) compared with traditional asphalt pavement. It is expected this study can provide insights for the development and implementation of PERS.

An acoustic nanogenerator based on porous PDMS/ZnO/PVDF-TrFE structure for self-powered intermediated-frequency sound monitoring

Abstract Sound energy is widely present in natural environment, nowadays predominantly collected using voluminous and heavy rigid devices, limiting their portability. Till now, there are few reports about using flexible materials to collect sound energy, and it is usually susceptible to environmental humidity. This study combines flexible polymer polydimethylsiloxane (PDMS), piezoelectric material polyvinylidene difluoride trifluoroethylene (PVDF-TrFE), nano zinc oxide (ZnO), and conductive carbon nanotubes (CNTs) to fabricate a porous nano ZnO/PVDF-TrFE/CNTs PDMS sound-driven nanogenerator (PZPCP SNG). It amalgamates frictional and piezoelectric effects: its porous structure enables efficient collection of vibration and frictional energy generated by sound waves; the piezoelectric effect of PVDF-TrFE and nano ZnO facilitates the conversion of acoustic mechanical energy, collectively enhancing the generator's output. Experimental optimization yields the best production conditions, achieving optimal outputs of 481.1 mV (open-circuit voltage), 209.13 nA (short-circuit current) under 400 Hz/125 dB sound stimuli, with a surface power density of 9.1 µW/m² (volumetric power density of 2.28 mW/m³). And it can convert sound ranging from 63-3000 Hz. With hardware circuitry, up to 5 series-connected light-emitting diodes (LEDs) can be illuminated within the circuit, demonstrating a certain degree of sound recognition capability. The proposed PZPCP SNG design is simple, effective, and lightweight, enabling flexible and stable intermediated-frequency acoustic energy harvesting. Its hydrophobic structural characteristics render it adaptable to various humidity, presenting a new approach toward widespread low-power sound detection and self-powering applications.

Optimizing Safety and Precision for Secondary Liposuctions: Integrating Intraoperative Ultrasound With VASER Technology.

Liposuction has gained significant popularity, leading to increased demand for secondary procedures due to complications such as scars and fibrosis that affect aesthetic outcomes. High-Definition Liposuction (HDL) has emerged as a preferred technique, but the presence of fibrosis from prior surgeries may limit its effectiveness. This study explores the application of ultrasound-assisted VASER (Vibration Amplification of Sound Energy at Resonance; VASER-Solta Medical, Bothell, WA) liposuction in secondary abdominal liposculpture to address these challenges. A prospective cohort study was conducted from May 2022 to May 2023, including patients undergoing secondary abdominal liposculpture with ultrasound-assisted VASER liposuction, at least 12 months post their initial procedure. Pre-operative ultrasound examinations were performed to identify and mark findings related to previous liposuction. Data on demographics, photographic results, and complications were collected and analyzed. Intraoperative ultrasound (I-US) significantly improved the detection of fibrotic lesions, leading to more precise, rapid, and atraumatic outcomes. The use of I-US optimized surgical procedures, reducing both costs and operation time. Clear communication with patients regarding potential limitations due to chronic damage was essential for setting realistic expectations. I-US has proven to be an invaluable tool in secondary liposculpture, enhancing surgical precision and outcomes. This methodology allows for better recognition of complications, promoting effective treatment strategies and ultimately improving patient satisfaction in the context of secondary abdominal liposculpture.

Revision of Sabine's and Eyring's reverberation theories

Sabine's and Eyring's reverberation theories are still the most important theoretical frameworks for room acoustics. The important physical quantities derived from these theories are the average sound pressure level (sound energy density) and the reverberation time (sound energy decay). Eyring revised Sabine's theory to become the reverberation time zero in the perfect absorption condition. However, Eyring's theory has contradictions regarding the sound energy density in a steady state and the energy decay from the steady state. In this study, in order to resolve these contradictions, the theoretical framework for the consistent system is presented introducing the new concept of the average impulse response in a room, and the contradictions in the current room acoustic theory are clarified. Based on the theoretical framework, Sabine's reverberation theory is revised by a different way of Eyring's theory. The reverberation time of the revised theory is shorter than that of Sabine's theory and longer than that of Eyring's theory. Finally, ray-tracing computer simulations were performed to verify the revised theory. Results of sound ray tracing simulations were in better agreement with the values calculated using the revised theory rather than those calculated using Sabine's and Eyring's theories.

Fundamental study on the difference between materials and vibration conditions in piezoelectric vibration power generation using electromechanical coupling phenomena

Conventionally, vibration energy and sound energy are emitted as noise and vibration. We have proposed a system that converts the vibration of the plate into energy. In this study, a circular plate of constant thickness, on which a piezoelectric element was installed, was adopted as the host structure of an energy-harvesting system. The plate was supported at its elastic end, which was intermediate between simple and clamped supports, and was subjected to a harmonic point force. The piezoelectric performance of the system was highly dependent on the vibration characteristics of the plate. Regarded as one of the representative vibrational characteristics, the natural frequency of the plate was affected by the materials, excitation positions, and vibration modes of the plate. Therefore, the plate materials varied the natural frequency, thus affecting the conversion of vibration energy into electrical energy through the piezoelectric effect. In this study, we investigated plates made of selected materials commonly used in industry and tested different excitation conditions. As the result, we clarified that the proposed system is almost unaffected by the material of the plates, and it was shown to be useful.

Sound source characteristics of heat exchanger under flow conditions

Heat exchangers are the most important equipment in ship cooling system, which generate vibration and noise due to flow excitation during operation, affecting structural safety and having a significant impact on acoustic stealth performance. Mastering the characteristics of sound source has guiding significance for noise reduction design. The acoustic signal directly obtained from the hydrophone inside the pipe including reflected sound wave, which cannot accurately characterize the sound radiation energy from heat exchanger into pipe. In order to accurately evaluate the sound source characteristics of heat exchanger under flow conditions, experimental method was used to test the sound source characteristics of heat exchanger which are not affected by connected pipelines based on the two-port sound source theory. The main factors affecting the sound source characteristics of heat exchanger were analyzed, such as flow rate, background pressure, and temperature. The research can provide reference for the vibration and noise reduction design of heat exchangers.

Determination of a diffusion coefficient function for long rooms using a least square optimization approach

Over the last decades, considerable attention has been devoted to improving the diffusion equation model within the field of room acoustics. It has been found that this model is subject to certain limitations, with one constraint regarding the diffusion coefficient. The diffusion coefficient, a parameter integrated into the model, is a value that scales the sound intensity to the gradient of the sound energy density. Currently, this value is often treated as a constant, but research has shown that it is spatially dependent. This paper explores a method to optimise the diffusion coefficient for long rooms such as corridors and tunnels by comparing the results of the diffusion equation model with those computed with the radiosity model and using the least-square optimization method, minimising the difference between the results of both methods. The parameters of a diffusion coefficient function are optimised, targeting a function that can be applied to a range of elongated spaces.

Sound propagation modelling in a street canyon by combining an image source model and impulse response measurements

This research introduces an innovative approach to achieve a computationally efficient model for calculating impulse responses in an urban environment, more precisely a street canyon, for auralization purposes. The image source method has shown its merits before, but when used for auralization, it typically lacks realism. In this study the image source method is used to create a basic impulse response of a street canyon, enriched by a stochastic response based on an envelope function. While the image source model accounts for the most prominent reflections, the stochastic part is due to all scattered sound energy in the street originating mainly from facade irregularities and street furniture. To obtain realistic frequency dependent envelope functions for various street canyon geometries, the function is based on measured impulse responses in nearly 100 inner-city street canyons in the city of Ghent, which were conducted by Thomas et al. (2013). By the proposed approach, we are able to generate impulse responses for street canyons suitable for sound perception research in an efficient way. More studies are needed to verify the applicability of the model for streets outside the Ghent dataset.

Prediction of the acoustic particle velocity in aerodynamic flows and its applications to the boundary element method

The acoustic variables are essential for understanding sound energy transmission and redistribution. The previous methods focused on acoustic pressure without the acoustic particle velocity, which is not enough for acoustic field evaluation. In this paper, an analytical formula for acoustic particle velocity prediction is developed based on the permeable surface integral solution of a vector wave equation. The validation examples are presented with stationary dipole and rotational monopole. The acoustic quantities, pressure, and velocity are solved at the same time and will be applied as input for the boundary element method (BEM) to evaluate the sound scattering problem in the frequency domain. Furthermore, the method is applied to study the acoustic field of flow passing a cylinder. The acoustic pressure shows good agreement with the flow observer. The acoustic particle velocity is also investigated.

Boundary-Element Analysis of the Noise Scattering for Urban Aerial Mobility Vehicles: Solver Development and Assessment

Abstract Urban aerial mobility (UAM) vehicles with multipropeller configurations have attracted considerable attention in recent years. However, previous investigations have mainly focused on the aerodynamic noise from individual propellers, with limited focus on the fuselage’s sound scattering effects which can alter the far-field noise directivity. In this work, an efficient boundary element solver for sound scattering was developed to fill this gap. The solver employs hierarchical matrices to save computational cost. The benchmark examples showed high accuracy and good scalability. A representative vehicle model was then chosen, and the propeller noise was simulated using rotating sources. Results show that the shielding effect in the fuselage/propeller configuration can produce an apparent noise reduction and redirect sound energy distribution, suggesting the importance of considering the fuselage in low-noise UAM development.

Temporal speech cue perception in listeners with cochlear implants depends on the time between those cues and previous sound energy.

Cochlear implants (CIs) provide precise temporal information that listeners use to understand speech. Other acoustic cues are not conveyed as precisely, making unambiguous temporal speech cues vital to a listener's ability to understand speech. Several speech sounds are differentiated by small differences in the timing of acoustic features. Previous studies have shown differences in the perception of these differences, depending on whether the speech sound was heard in a single word or embedded in a sentence. This study expands on previous research by exploring forward masking as a possible contributor to the mechanisms driving the effects observed when temporal cues were embedded in sentences. Listeners using CIs performed a phoneme categorization task on words from four continua that each varied mainly on a single temporal dimension. The differentiating phonemes were located at the beginning of the word in two continua and at the end of the word in two others. Silent intervals of 0, 25, 50, 75, and 100 ms between the preceding sentence and the target words were tested. Results showed an increasing effect on performance as the inter-stimulus interval duration decreased for the two word-initial phonemic contrasts, lending support to forward masking as an influence on speech understanding.

Theory and Design of Audio Rooms: Physical Formulation

The time-dependent statistical chains of transition matrix B are successfully used to calculate the reverberation time TR and sound energy density field in audio rooms. This is a real breakthrough in the search for a statistical derivation of Sabines' imperial theory which has never been rigorously proven since 1898. Additionally, we provide proper design and calculations of sound wave energy density in audio rooms via two cuboid room examples. We provide proper design and calculations of sound wave energy density in audio rooms via two cuboid room examples. We also propose some general statistical rules that can be applied to statistical problems of physical phenomena in general, such as the thermal diffusion equation and the theory of sound waves in audio rooms. We also give a description of the theory and design of what we call comfortable sound rooms based on the purpose of their use via well-defined measurables. Finally, we provide a consistent derivation of Sabines' theory without using Ls=4V/A or any other statistical assumptions.

Study on multi-degree-of-freedom septum liners for broadband noise reduction

Silent aeroengine nacelle highlights the demand for advanced acoustic liners providing broadband absorption. This paper studies the multi-degree-of-freedom (MDOF) septum liner that is a promising candidate. The steady-flow resistance of the septum as the necessary input parameter is measured on a steady-flow resistance tube herein, and an impedance prediction model is introduced and validated through the experimental measurement and the numerical simulation. Then, three liners with embedded septa of varied types, numbers and depths are designed, and the acoustic characteristics are analyzed in a wide frequency range under different incident sound pressure levels (SPL). It indicates that such liners can perform well in an ultra-broadband range up to 10000 Hz, and the impedance is relatively insensitive to the incident SPL. It is worth noting that, achieving broadband absorption for such liners is influenced by the coupling effect between zeros of the reflection coefficient, which correspond to the resonance frequencies of the liner. Moreover, the simulated results illustrate that the significant absorption for MDOF septum liners stems mainly from the sound energy dissipation at specific spatial positions depending on the frequency.

Unprecedented mechanical wave energy absorption observed in multifunctional bioinspired architected metamaterials

In practical engineering, noise and impact hazards are pervasive, indicating the pressing demand for materials that can absorb both sound and stress wave energy simultaneously. However, the rational design of such multifunctional materials remains a challenge. Herein, inspired by cuttlebone, we present bioinspired architected metamaterials with unprecedented sound-absorbing and mechanical properties engineered via a weakly-coupled design. The acoustic elements feature heterogeneous multilayered resonators, whereas the mechanical responses are based on asymmetric cambered cell walls. These metamaterials experimentally demonstrated an average absorption coefficient of 0.80 from 1.0 to 6.0 kHz, with 77% of the data points exceeding the desired 0.75 threshold, all with a compact 21 mm thickness. An absorptance-thickness map is devised for assessing the sound-absorption efficiency. The high-fidelity microstructure-based model reveals the air friction damping mechanism, with broadband behavior attributed to multimodal hybrid resonance. Empowered by the cambered design of cell walls, metamaterials shift catastrophic failure toward a progressive deformation mode characterized by stable stress plateaus and ultrahigh specific energy absorption of 50.7 J/g—a 558.4% increase over the straight-wall design. After the deformation mechanisms are elucidated, a comprehensive research framework for burgeoning acousto-mechanical metamaterials is proposed. Overall, our study broadens the horizon for multifunctional material design.

Electrical-Modulated Flexible Acoustic Metamaterial: Enhancing Low-Frequency Absorption via an Ionic Electroactive Polymer.

The growing concern over low-frequency noise pollution resulting from global industrialization has posed substantial challenges in noise attenuation. However, conventional acoustic metamaterials, with fixed geometries, offer limited flexibility in the frequency range adjustment once constructed. This research unveiled the promising potential of ionic electroactive polymers, particularly ionic polymer-metal composites (IPMCs), as a superior candidate to design tunable acoustic metamaterial due to its bidirectional energy conversion capabilities. The previously perceived limitations of the IPMC, including slow reaction and high energy expenditure, owning to its inherent sluggish intermediary ionic mass transport process, were astutely leveraged to expedite the attenuation of low-frequency sound energy. Both our experimental and simulation results elucidated that the IPMC can generate voltage potentials in response to acoustic pressure at frequencies significantly higher than those previously established. In addition, the peak absorption frequency can be effectively shifted by up to 45.7% with the application of a 4 V voltage. By further integration with a microperforated panel (MPP) structure, the developed metamaterial absorbers can achieve complete sound absorption, which was continuously tunable under minimal voltage stimulation across a wide frequency spectrum. In addition, a microslit structure IPMC metamaterial absorber was designed to realize modulation of the perforation rate, and the absorption peak can be shifted by up to 79.2%. These findings signify a pioneering application of ionic intelligent materials and may pave the way for further innovations of tunable low-frequency acoustic structures, ultimately advancing the pragmatic deployment of both soft intelligent materials and acoustic metamaterials.