Sound Pressure Research Articles

Acoustically Enhanced Triboelectric Stethoscope for Ultrasensitive Cardiac Sounds Sensing and Disease Diagnosis.

Electronic stethoscope used to detect cardiac sounds that contains essential clinical information is a primary tool for diagnosis of various cardiac disorders. However, the linear electro-mechanical constitutive relation makes conventional piezoelectric sensors rather ineffective to detect low-intensity, low-frequency heart acoustic signal without the assistance of complex filtering and amplification circuits. Herein, we find that triboelectric sensor features superior advantages over piezoelectric one for micro-quantity sensing originated from the fast saturated constitutive characteristic. As a result, the triboelectric sensor shows ultrahigh sensitivity (1215mV/Pa) than the piezoelectric counterpart (21mV/Pa) in the sound pressure range of 50 - 80dB under the same testing condition. By designing a trumpet-shaped auscultatory cavity with a power function cross-section to achieve acoustic energy converging and impedance matching, triboelectric stethoscope delivers 36dB signal-to-noise ratio for human test (2.3 times of that for piezoelectric one). Further combining with machine learning, five cardiac states can be diagnosed at 97% accuracy. In general, the triboelectric sensor is distinctly unique in basic mechanism, provides a novel design concept for sensing micromechanical quantities, and presents significant potential for application in cardiac sounds sensing and disease diagnosis. This article is protected by copyright. All rights reserved.

Optimizing the noise control in a two-layer conduit

In the modern world, noise pollution is a major concern due to its prevalence. This work focuses on optimizing noise control in a two-layer conduit. A conduit comprises an inlet and double-outlet zones (DOZ). The upper walls of the DOZ are lined with perforated absorbent material while the lower walls are layered with fibrous. Mathematically, the physical problem is formulated with a field wave equation together with rigid and impedance boundary conditions in the respective zones. Such governing boundary value problem (BVP) leads to the Sturm-Liouville (SL) category in which standard orthogonality relations (OR) are indispensable. The system of the linear equations of the BVP is acquired with semi-analytical Mode-Matching (MM) approach by implementing the continuity conditions of sound pressures and velocities at the matching junction with the aid of OR. These systems are truncated and solved numerically with computation learning to obtain the reflected and transmitted modal amplitudes in respective zones. Due to the lining's perforated upper walls, fibrous lower walls, and reversal in the DOZ, the analysis of the reflected and transmitted powers versus frequencies is significantly observed and is shown in graphical findings. The algebraic derivation is validated by satisfying the conservation law of power flux and matching continuity conditions for impedance, perforated, and fibrous lined boundaries.

Acoustical analysis and optimization design of the hair dryers

Abstract The sound qualities and wind speeds of the four commercial hair dryers (Panasonic, Confu, Flyco, and Philips) were investigated through experimental methods in the present study. The sound qualities included loudness, sharpness, roughness, and fluctuation strength. The experimental results showed that the maximum sound pressure level (SPL) of all hair dryers occurred at about 200 Hz except Flyco hair dryer, which occurred at about 400 Hz. The highest loudness and highest sharpness were found when the hair dryers were set to hot mode and cold mode, respectively. No consistent relationship was found between the effect of room space and SPLs of the hair dryers. The Box–Behnken design method was used to design 13 pieces of oval and rectangular nozzles, and their sound levels and wind speeds were measured. Thereafter, these experimental results were used to derive correlation coefficients between the hair dryer nozzle area, aspect ratio, nozzle length, loudness, and wind speed using the Anova analysis method. Finally, an oval nozzle and a rectangular nozzle with an area of 0.0005 m 2 {}^{2} , an aspect ratio of 1, and nozzle lengths of 0.052 and 0.055 m, respectively, were designed and were tested. These nozzles managed to reduce the sound loudness by 15 and 9.6%, respectively, while maintaining the same level of wind speed.

C-Phycocyanin Attenuates Noise-Induced Cochlear Synaptopathy via the Inhibition of Oxidative Stress and Intercellular Adhesion Molecule-1 in the Cochlea

The synapses between inner hair cells (IHCs) and spiral ganglion neurons (SGNs) are the most vulnerable structures in the noise-exposed cochlea. Cochlear synaptopathy results from the disruption of these synapses following noise exposure and is considered the main cause of poor speech understanding in noisy environments, even when audiogram results are normal. Cochlear synaptopathy leads to the degeneration of SGNs if damaged IHC-SGN synapses are not promptly recovered. Oxidative stress plays a central role in the pathogenesis of cochlear synaptopathy. C-Phycocyanin (C-PC) has antioxidant and anti-inflammatory activities and is widely utilized in the food and drug industry. However, the effect of the C-PC on noise-induced cochlear damage is unknown. We first investigated the therapeutic effect of C-PC on noise-induced cochlear synaptopathy. In vitro experiments revealed that C-PC reduced the H2O2-induced generation of reactive oxygen species in HEI-OC1 auditory cells. H2O2-induced cytotoxicity in HEI-OC1 cells was reduced with C-PC treatment. After white noise exposure for 3 h at a sound pressure of 118 dB, the guinea pigs intratympanically administered 5 μg/mL C-PC exhibited greater wave I amplitudes in the auditory brainstem response, more IHC synaptic ribbons and more IHC-SGN synapses according to microscopic analysis than the saline-treated guinea pigs. Furthermore, the group treated with C-PC had less intense 4-hydroxynonenal and intercellular adhesion molecule-1 staining in the cochlea compared with the saline group. Our results suggest that C-PC improves cochlear synaptopathy by inhibiting noise-induced oxidative stress and the inflammatory response in the cochlea.

Numerical prediction of mean flow and acoustic field of a supersonic impinging jet

The three-dimensional turbulent mean flow and acoustic field of a supersonic jet impinging on a solid plate is studied computationally using the general purpose CFD code Ansys Fluent. A pressure-based coupled solver formulation with the second order weighted central-upwind spatial discretization is applied to compute transient solutions. Cold and hot jet thermal conditions are considered. Mean flow characteristics are investigated by a steady-state modeling approach. Acoustic radiation of impingement tones is simulated using a transient time-domain formulation. The effects of turbulence in steady-state are modeled by the SST k-ω turbulence model. The Wall-Modeled Large-Eddy Simulation (WMLES) model is applied to compute transient solutions. The near-wall mesh on the impingement plate is fine enough to resolve the viscosity-affected near-wall region all the way to the laminar sublayer. Nozzle-to-plate distance is parameterized in the model for automatic re-generation of the mesh and results. Steady-state predictions of hover lift loss and mean jet velocity distributions are compared with experimental data, and favorable agreement is reported. The transient solution reproduces the mechanism of impingement tone generation by the interaction of large scale vortical structures with the impingement plate. The acoustic near-field is directly resolved by Computational Aeroacoustics (CAA) to accurately propagate impingement tone waves to near-field microphone locations. Calculated impingement tone frequencies and sound pressure levels agree with experimental values.

Sound pressure level determination around the transformer using coherent and incoherent analytical summation methods

In this paper, coherent and incoherent analytical summation methods from elementary sound sources on the transformer’s tank are presented. They aim to determine a one-third-octave spectrum of sound pressure levels (SPL) in points around the transformer. Each part of the transformer’s surface is treated as a separate plane source so the analytical calculation can be applied to find SPL in the surroundings. Reflections from the ground are also considered by putting an image of the plane sources on the other side of the reflecting plane and adding its contributions to the total pressure in the desired points. Grid-like vibration measurements of vibration velocity on the tank surfaces are used as input parameters. Vibrations and sound pressure levels are measured to validate the method on the 5 MVA transformer experimental object. The SPL around the transformer in short-circuit (SC) and open-circuit (OC) tests is measured in the semi-anechoic chamber to compare it with theoretical results. By analyzing the results, the coherent calculation with reflection provided the most accurate results. In the SC operating condition, the normalized root mean square error (NRMSE) is 17.2%, and in the OC operating condition, it is 10.9%. The novelty of the presented method is that it considers complicated transformer geometry where each surface is calculated as a separate noise source. It calculates noise at a distance from the elementary vibration sources, considering phase and reflection from the hard ground, and provides detailed noise maps that can be used for noise modeling around the substations.

Design Approaches and Electromechanical Modeling of Conformable Piezoelectric‐Based Ultrasound Systems

AbstractPainless, needleless delivery of drugs through the skin can be realized through aphenomenon called sonophoresis by applying an ultrasound field to the biological tissue. Development of wearable embodiments of such systems demands comprehensive characterization of both the physical mechanism of sonophoresisas well as wearability parameters. Here, we present a framework for analyzing disk‐type piezoelectric transducers in a polymeric substrate to create acoustic cavitation in a fluid coupling medium for sonophoresis applications. The device design and operating parameters such as the working frequency, applied voltage range, acoustic pressure distribution, and transducer spacing were determine dusing a finite element methods (FEM),and verified with experimental measurements. The influence of the surrounding water and tank reflections on the acoustic pressure field, and the interaction between the elements in the array structure were also studied.Finally, the impact of skin and the substrate geometry on the acoustic pressure fields was characterized to simulate the invivo use‐case of the system. These analytical models can be used to guide critical parameters for device design such as the separation distance of the piezoelectric transducer from the skin boundary. We envision that this tool boxwill support rapid design iteration for realization of wearable ultrasound systems.

Recent Advances in Ferroelectret Fabrication, Performance Optimization and Applications.

The growing demand for wearable devices has sparked a significant interest in ferroelectret films. They possess flexibility and exceptional piezoelectric properties due to strong macroscopic-dipoles formed by charges trapped at the interface of their internal cavities. This review of ferroelectrets focuses on the latest progress in fabrication techniques for high temperature resistant ferroelectrets with regular and engineered cavities, strategies for optimizing their piezoelectric performance, and novel applications. The charging mechanisms of bipolar and unipolar ferroelectrets with closed and open-cavity structures are explained first. Next, the preparation and piezoelectric behavior of ferroelectret films with closed, open and regular cavity structures using various materials are discussed. Three widely used models for predicting the piezoelectric coefficients (d33) are outlined. Methods for enhancing the piezoelectric performance such as optimized cavity design, utilization of fabric electrodes, injection of additional ions, application of DC bias voltage and synergy of foam structure and ferroelectric effect are illustrated. A variety of applications of ferroelectret films in acoustic devices, wearable monitors, pressure sensors and energy harvesters are presented. Finally, the future development trends of ferroelectrets towards fabrication and performance optimization are summarized along with its potential for integration with intelligent systems and large-scale preparation. This article is protected by copyright. All rights reserved.

Symphonies of Growth: Unveiling the Impact of Sound Waves on Plant Physiology and Productivity

The application of sound wave technology to different plant species has revealed that variations in the Hz, sound pressure intensity, treatment duration, and type of setup of the sound source significantly impact the plant performance. A study conducted on cotton plants treated with Plant Acoustic Frequency Technology (PAFT) highlighted improvements across various growth metrics. In particular, the treated samples showed increases in the height, size of the fourth expanded leaf from the final one, count of branches carrying bolls, quantity of bolls, and weight of individual bolls. Another study showed how the impact of a 4 kHz sound stimulus positively promoted plant drought tolerance. In other cases, such as in transgenic rice plants, GUS expression was upregulated at 250 Hz but downregulated at 50 Hz. In the same way, sound frequencies have been found to enhance the osmotic potential, with the highest observed in samples treated with frequencies of 0.5 and 0.8 kHz compared to the control. Furthermore, a sound treatment with a frequency of 0.4 kHz and a sound pressure level (SPL) of 106 dB significantly increased the paddy rice germination index, as evidenced by an increase in the stem height and relative fresh weight. This paper presents a complete, rationalized and updated review of the literature on the effects of sound waves on the physiology and growth parameters of sound-treated plants.

Estimation of the effect of thin-plated surface on a three-staged looped thermoacoustic engine for low-grade heat recovery

This paper introduces two novel structures of looped thermoacoustic engines designed for outdoor low-frequency sound sources. The system consists of three thermoacoustic engines in a loop and a stub for sound radiating, which is characterized by reliability, high efficiency, and compactness. Two thin plates are used to prevent the Gedeon flow, facilitate sound propagation, and adjust the acoustic field. The system with a straight stub achieved a maximum Sound Pressure Level of 126.09 dB at 1 m away, surpassing highest reported records by 25.96 %. The system also achieves a high output efficiency of 3.86 %. The system with tapered stub and a 0.1 mm silicone plate, achieved an SPL of 120.76 dB at 1 m. To maintain the predetermined acoustic field, it is important to consider a thin plate with small Young's modulus and thickness. The effect on the acoustic field must be considered when the thickness exceeds 0.8 mm. The addition of the 0.28 mm thin plate in system with tapered stub resulted in a 7.8 W increase in acoustic power compared to that of system without the thin plate.

Experimental Study of Laser-Induced Cavitation Bubbles near Wall: Plasma Shielding Observation

To investigate the plasma shielding of laser-induced cavitation bubbles near a wall, a pulsed laser with different energies was selected to induce cavitation bubbles on the surface of 7050-T7451 aluminum alloy. A high-speed camera captured the evolution of the cavitation bubble, while a fiber-optic hydrophone system collected the acoustic signals during the evolution. Finally, a confocal microscope was used to view and analyze the surface morphology of 7050 aluminum alloy. The experimental results indicate that as the laser energy increases, the diameter, the evolution time, the pressure of the bubble, and both the pit diameter and depth all increase. Beyond an energy level of 1.4 J, the maximum diameter and the evolution time of the laser-induced cavitation bubble begin to decrease; the maximum diameter decreases by 2.04%, and the first evolution time decreases by 3.26%. Plasma shielding was observed in this experiment. Considering that the essence of a laser-induced cavitation bubble is the interaction between a high-energy laser and a liquid medium, the abnormal decrease in the maximum diameter, evolution time, and sound pressure epitomizes the manifestation of plasma shielding.

Vibration and underwater noise simulation of a river-crossing tunnel based on a 2.5D structural-acoustic finite element method

To protect the underwater ecosystem and species, the vehicle-induced vibration and underwater radiated noise of river-crossing tunnels need to be calculated efficiently and accurately. For this purpose, this study proposed a 2.5-dimensional (2.5D) structural-acoustic finite element method which combines 2.5D finite element vibration algorithm and 2.5D infinite element acoustic algorithm. The proposed method utilizes the spatial wave number transformation theory and the acoustic transfer vector (ATV) method. Based on a river-crossing tunnel, a 2.5D numerical simulation model was established in this study to analyze the vehicle-induced tunnel-soil vibration as well as the underwater radiated noise during operation. The results showed that the tunnel vibration and the associated radiated noise mainly distributed in the range of 10 to 40 Hz, with two peaks at 15.6 Hz and 31.5 Hz, respectively. The total sound pressure level (SPL) of the predicted noise at each field point reached a maximum value of 126 dB. The 2.5D algorithm proposed in this study achieves higher computational efficiency compared to traditional 3D vibration and noise analysis methods, which can provide theoretical and technical supports for the protection of underwater ecological diversity.

Traffic noise measurement, mapping, and modeling using soft computing techniques for mid-sized smart Indian city

The present study presents an investigation into the utilization of artificial neural networks (ANN) and multiple linear regression model (MLR) for the prediction of traffic noise levels in various locations of Dhanbad city at varying intervals. Traffic noise indices measurements were carried out using sound pressure level meter (SLM). The prediction of equivalent A-weighted sound level (LAeq) and the sound level exceeding 10 percent of the time (L10) is carried out using various influencing factors such as number of cars, number of 2 wheelers, number of 3 wheelers, number of heavy vehicle, number of medium commercial vehicles, and traffic speed. The findings demonstrate the ANN model's proficiency in comparison of MLR model for providing precise prediction accuracy of traffic noise indices with a R2 of 0.94 for LAeq and 0.91 for L10. Furthermore, the frequency spectrum analysis reveals that high peaks were observed at lower frequencies ranging from 31.5 Hz to 50 Hz, middle frequencies from 500 to 800 Hz and higher frequencies from 3.5 kHz to 5 kHz. The noise maps at varying intervals revealed that most of the locations are having higher noise levels due to increase in vehicular movement. The study emphasizes on the potential significance of the proposed neural network-based prediction model in collaboration with noise mapping as a vital tool for the anticipation of traffic noise levels and the formulation of noise mitigation strategies in context of the mid-sized smart city like Dhanbad, India.

Extension of interval between adjacent pulse delivery cycles to deal with myocardial ischemia by intravascular lithotripsy: case report

BackgroundIntravascular lithotripsy (IVL) represents a novel approach in the management of coronary calcification. This technique employs acoustic pressure waves, generated by a shockwave balloon, to effectively fracture both superficial and deep calcification in situ. The efficacy and safety of IVL have been convincingly demonstrated through the Disrupt CAD I-IV studies. While IVL is associated with the occurrence of atrial and ventricular arrhythmias, there is no evidence to indicate it causes myocardial ischemia.Case DescriptionA 71-year-old man was admitted presenting with chest pain. His previous coronary angiography revealed stenosis and calcification in the left anterior descending branch. An attempt to predilate the lesion using two Lacrosse non-slip element balloons was unsuccessful. Ventricular premature beats and transient ST-segment depression were captured during the utilization of IVL. The operator gradually extended the pulse emission interval across two consecutive cycles to mitigate myocardial ischemia. Notably, when the interval reached 30s, the patient had no chest pain or ST-segment changes. Subsequent images of intravascular ultrasound confirmed calcification ruptures. Therapeutic intervention included the placement of a stent and the application of a drug-coated balloon in the left anterior descending branch. A telephonic follow-up six months later indicated the patient had no discomfort.ConclusionsThis case underscores the effectiveness of gradually extending the pulse emission interval as a strategic complement to the clinical application of IVL. In certain clinical scenarios, it may become imperative to suspend the pulse delivery to improve myocardial blood supply.

Optimal treatment conditions for low-intensity pulsed ultrasound therapy for Alzheimer's disease: applications from mice to humans.

We previously developed a novel therapy with low-intensity pulsed ultrasound (LIPUS) that ameliorates cognitive decline through upregulation of endothelial nitric oxide synthase (eNOS) in mouse models of Alzheimer's disease (AD). In a randomized, double-blind, placebo-controlled pilot trial, we demonstrated that whole-brain LIPUS therapy is safe and tends to suppress the cognitive decline in early AD patients. We herein report the findings of our basic experiments that we performed for the pilot trial in order to apply whole-brain LIPUS therapy to humans, as well. First, we examined the relationship between bone density/thickness and ultrasound transmittance using human temporal bone. Next, based on the results of ultrasound transmittance, we further examined mRNA expression of VEGF, FGF2, and eNOS in response to variable ultrasound frequencies, duty cycles, and sound pressures. There was a significant correlation between bone thickness and transmittance (1.0MHz, P < 0.001), while there was no significant correlation between bone density and transmittance (1.0MHz, P = 0.421). At a frequency of 0.5MHz, the optimum duty cycle was considered to be up to 20%. When the tissue amplitude was in the range of 0.05-0.5MPa, VEGF, FGF2, and eNOS were significantly upregulated by LIPUS. Thus, the conditions necessary for LIPUS therapy for the human brain were identified as sound pressure just below the probe 1.3MPa (tissue amplitude 0.15MPa), duty cycle 5%, and frequency 0.5MHz. We successfully identified the optimal treatment conditions for LIPUS therapy for patients with AD.

Directional Multi-Resonant Micro-Electromechanical System Acoustic Sensor for Low Frequency Detection.

This paper reports on the design, modeling, and characterization of a multi-resonant, directional, MEMS acoustic sensor. The design builds on previous resonant MEMS sensor designs to broaden the sensor's usable bandwidth while maintaining a high signal-to-noise ratio (SNR). These improvements make the sensor more attractive for detecting and tracking sound sources with acoustic signatures that are broader than discrete tones. In-air sensor characterization was conducted in an anechoic chamber. The sensor was characterized underwater in a semi-anechoic pool and in a standing wave tube. The sensor demonstrated a cosine-like directionality, a maximum acoustic sensitivity of 47.6 V/Pa, and a maximum SNR of 88.6 dB, for 1 Pa sound pressure, over the bandwidth of the sensor circuitry (100 Hz-3 kHz). The presented design represents a significant improvement in sensor performance compared to similar resonant MEMS sensor designs. Increasing the sensitivity of a single-resonator design is typically associated with a decrease in bandwidth. This multi-resonant design overcomes that limitation.

Parameter identification and NVH characteristic analysis of automotive suspension rubber bushing

Accurate prediction of the dynamic stiffness of rubber bushings is crucial for optimizing vehicle vibration and noise performance. However, this task is highly challenging due to various influencing factors such as frequency and amplitude. Consequently, there has been limited research conducted in this area thus far. This paper presents a novel approach for predicting the dynamic stiffness of rubber bushings. The frequency and amplitude dependencies of rubber bushings were thoroughly investigated through dynamic loading tests. A comprehensive model for rubber bushings, incorporating parallel connections of elastic elements, friction elements, and higher-order fractional derivative viscous elements, was established. The model parameters were accurately identified using the GA-BP method. The results demonstrate that the proposed model exhibits a high level of precision in estimating dynamic stiffness across a frequency range of 0–200 Hz. In comparison to the conventional model, the proposed approach enables more precise computation of interior sound pressure response and enhances vehicle simulation accuracy.

Nonlinear vibration and acoustic radiation of an internally resonant buckled beam

Although the nonlinear vibration of buckled beam has been thoroughly studied, its acoustic radiation does not get much attention. This paper deals with the nonlinear vibro-acoustic problem of an internally resonant buckled beam immersed in an infinite fluid. A finite element method based on an arbitrary Lagrangian-Eulerian framework is adopted to analyze the nonlinear interaction between the large-deformed buckled beam and the finite-amplitude acoustic waves in the fluid. The effects of acoustic pressure excitation, external harmonic excitation, and internal resonance on the vibro-acoustic responses of the buckled beam are discussed in the first and second primary resonances. It is found that the amplitude of the acoustic pressure can be comparable to the amplitude of the external harmonic force. This leads to an increase in the critical harmonic excitation amplitude for the occurrence of quasi-periodic responses and an increase in the second mode frequency component of quasi-periodic responses compared to the case neglecting the acoustic pressure excitation on the beam. Saturation phenomena are discovered in the second mode frequency components of beam displacement and acoustic pressure. Due to the 2:1 internal resonance, different time-frequency characteristics, quadrupole acoustic directivity patterns with low radiation efficiency, and dipole acoustic directivity patterns with high radiation efficiency can be observed at different harmonic excitation amplitudes and frequencies. Understanding these phenomena will help design loudspeakers and recognize sound sources.

Experimental study on spatial distribution law of traffic noise on urban viaduct

Traffic noise is the main environmental pollution of the elevated line. In order to prevent and control this noise, it is necessary to understand the spatial distribution of the noise. In this paper, the noise monitoring and data fitting of representative points near the Ningbo viaduct are carried out by means of the field test. By setting measuring points at different distances and heights perpendicular to and parallel to the elevated line, the spatial distribution law of noise near the elevated line is studied. The results show that: (1) The noise in the transverse direction of the bridge decreases in a logarithmic curve with the increase of the vertical distance between the measuring point and the viaduct; (2) The noise along the bridge decreases in a logarithmic curve with the increase of the vertical distance between the measuring point and the intersection; (3) The noise in the elevated direction first increases with the rise of the floor, reaching the maximum on floors 10-12, and the sound pressure on floors 12-20 is basically stable.

Acoustic condition monitoring of coffee beans, during the roasting process

The research results presented here deal with the acoustic condition monitoring of coffee beans during the roasting process. In particular, the question was investigated whether the current state (roasting level) of the coffee beans during the roasting process can be detected by acoustic monitoring. To answer this question, an experiment was carried out with a sample drum roaster (Hottop KN-8828B- 2K+) in which the airborne sound pressure was recorded for five different roasting methods and then examined. The methods used differed in the inner temperature of the roaster when the coffee beans were inserted (75◦C, 100◦C, 150◦C, 175◦C, 200◦C). The recording of the roasting processes has been made by two microphones placed in front of the drum, with each process being repeated five times. To enable a comparison between the different processes, five points at which the coffee beans had reached a certain temperature were determined for each grating. Five sequences of equal length were then cut from each recording, with the determined time points serving as the starting value of the sequence.First, the differences in the spectral composition of the signals in the first and second crack were investigated and compared with those in other past publications. Furthermore, the comparison of the behavior as a function of the throw-in temperature has been investigated. For most of the processes analysed, the sound pressure levels can be clearly separated as a function of the bean temperature. In conclusion, it was shown that sound analysis can be used to determine the proportion of cracked beans.