Reflection Of Sound Waves Research Articles

Indoor self-localization using multipath arrival time measured by a single acoustic ranging sensor

The objective of this study is to achieve vehicle self-localization using a single acoustic ranging sensor in a multipath environment. For this purpose, we proposed a measurement method of multiple time-of-flight (ToF) using an acoustic ranging sensor and a self-localization method using the ToFs. The proposed method predicts the ToFs based on the wall position and the predicted self-location and corrects the self-location by comparing it with the actual ToFs. Sound waves radiated indoors are reflected multiple times by every wall, ceiling, and floor. Therefore, the observed signal contains multiple reflected waves. Since the conventional method only considers a single reflection, self-localization becomes challenging in a multiple reflection environment. We showed that the estimation accuracy can be improved by utilizing the multiple reflections of sound waves in three-dimensional space and modeling them. The experiments confirm that the average location error of the proposed method is 0.084 m.

Two dimensional echocardiography as an evidence for clinically significant murmur

Background: Heart murmurs are extra and abnormal sounds made by turbulent flow of blood through heart. The most common cardiac abnormality found on auscultation is murmur. Edler is regarded as father of echocardiography. This is based on reflection of sound waves by heart structures similar to the radio detection and ranging (RADAR) and sound navigation and ranging (SONAR).Methods: Our study was done in PICU of Kempegowda Institute of Medical Sciences hospital, Bangalore. Duration of study was 6 years that is from January 2015 to January 2020. During this period total 2304 pediatric cases with various diseases were admitted. Of these 150 (6.5%) children were having clinically significant murmur. All children who fulfilled inclusion criteria were subjected to 2d echo by GE VIVID portable 2 dimensional and colour Doppler echocardiography trans-thoracically.Results: 96 (64%) children had abnormal 2d echo. Of these 37 (38.5%) children were found to have organic heart disease and 59 (61.5%) had functional heart disease. Of these 37 children 10 (27%) had pulmonary arterial hypertension (PAH), 8 (21%) children had atrial septal defect, 7 (18%) had perforated foramen ovale (PFO), 2 (5%) had mitral valve prolapse, 2 (5%) had ventricular septal defect (VSD), 1(2%) had tetralogy of fallot (TOF), 1 (2%) had septal aneurysm, and 1 (2%) had pericardial effusion.Conclusions: There is 64% chances of detecting a heart disease, if 2D echo is done in children with clinically significant cardiac murmur. Hence 2D echo is a vital investigation in evaluating heart murmurs.

Side-Scan Sonar Analysis Using ROI Analysis and Deep Neural Networks

Side-scan sonar generates an image based on the reflection of sound waves. The reflection takes place with the first encountered object, which, in practice, may be a passing fish or even a wave from the boat turbine. Therefore, such data are sensitive to all noises. In this article, we propose a real-time automatic system of side-scan sonar analysis that can detect and classify different objects. Our proposition is based on the processing of a given image to quickly verify whether there is anything other than the bottom of the river/sea. If so, this image is analyzed in terms of regions of interest (ROIs) by the histogram module. This action allows the extraction of only objects of interest, which are then classified by convolutional neural networks (CNNs). A proposed model also contains an automatic mechanism of adding the sample to the database in order to later guarantee the accuracy of the classifiers. The model is a hybridization of image processing techniques with a machine learning approach to analyze difficult images. The presented system has been tested on the bottom of a river in Szczecin, Poland. We reached 90% of accurate classification in case scenario and 88% in simulation on used datasets. The obtained results were presented and discussed in terms of the advantages of practical application in analyzing side-scan sonar images.

Reflection and Refraction of Sound Waves at the Interface between a Bubbly Liquid and a Porous Medium Saturated with a Bubbly Liquid

Reflection and Refraction of Sound Waves at the Interface between a Bubbly Liquid and a Porous Medium Saturated with a Bubbly Liquid

Reflection and transmission of cylindrical sound wave through an elastic plate with an inhomogeneous coating

Reflection and transmission of cylindrical sound wave through an elastic plate with an inhomogeneous coating

Reflection and transmission of cylindrical sound wave through an elastic plate with an inhomogeneous coating

Reflection and transmission of cylindrical sound wave through an elastic plate with an inhomogeneous coating

Application of partial areas method in the problem of sound radiation by a sphere in a waveguide with soft acoustically boundaries

The paper considers the features of the formation of an acoustic field by a spherical source with complicated properties in a regular plane-parallel waveguide, which is of practical importance in marine instrumentation and oceanographic research. The calculation algorithm is based on the use of the Helmholtz equation and the Fourier method for each partial region and the conjugation conditions on their boundaries. The presented calculation allows one to get rid of the idealized boundary conditions on the source surface, with the subsequent determination of the excitation coefficients of the waveguide modes within the framework of the Sturm-Liouville problem. In this case, the attraction of the boundary conditions on the surface and the bottom of the sea, as well as the Sommerfeld conditions, makes it possible to obtain the real distribution of the field in the vertical sections of the waveguide. The obtained frequency dependences of the pressure and vibrational velocity components show their amplitude-phase differences, which reach 90 degrees, which partially explains the appearance of singular points in the intensity field in a regular waveguide. It has been determined that multiple reflections of sound waves from the boundaries of the working space and the space of the waveguide cause oscillations of the pressure components with a change in the amplitude level up to 6 dB. It was found that with an increase in the size of the source, a kind of resonance is formed in the working space, the frequency of which depends on the depth of the sea and corresponds to the region kr=x=5.8. It was found that when the acoustic field is formed in the working space, the frequency response of the impedance components is represented as a multiresonant dependence formed on the basis of the frequency characteristics of the lower modes and their combinations. Experimental studies have shown that the results of calculations of the mode composition of the acoustic field of the emitter, obtained in the conditions of the pool, correspond to the spatial characteristics of the mode components of the acoustic field with an error of up to 3 dB

Analysis of Directional Properties of Angular Horn Antenna

In this paper, horn antennas are considered to belong to the class of aperture antennas which usually include a sound wave reflector and an electroacoustic transducer. For the variant of technical implementation of the electroacoustic transducer in the form of a corner antenna, the problem of sound emission by such an antenna is solved . taking into account the repeated reflection of emitted sound waves from the antenna design elements. The study of the acoustic properties of such an antenna was carried out taking into account a number of assumptions. 'what material, the thickness of the walls of the mouthpiece is infinitesimal. These conditions are supplemented by the known conditions of radiation at infinity. All the above assumptions make it possible to greatly simplify the solution of the problem of sound radiation by an angular horn antenna. To do this, the Helmholtz equation under boundary conditions was solved by the method of connected fields in multiconnected domains, corresponding to the physical model of the antenna. The radiation field of such an antenna is presented in the form of three partial regions, which in turn, according to the method of partial regions - in the form of Fourier series expansions, the coefficients of which are determined by solving differential equations describing piezoceramic transducer oscillations and wave processes. in acoustic environments in contact with it. The solution of the Helmholtz equation is reduced to the solution of an infinite system of linear algebraic equations taking into account the above assumptions, as well as the conditions of field continuity at the boundary of partial domains, we obtain an infinite system of linear algebraic equations. Based on the system, an approximate expression for the normalized radiation pattern is obtained. Studying the features of the directional properties of the angular antenna by direct analysis of the expression is not possible. Therefore, such a study was carried out on the basis of calculated directivity diagrams obtained using a computer for a wide range of wave sizes and geometrical characteristics of the angular antenna. cylindrical electroacoustic transducers. In all calculations, a uniform distribution of the oscillating velocity on the surface of the emitter was chosen Analyzing the obtained data, there is a pronounced dependence of the shape of the pattern on the magnitude of the wave size of the speaker. This is manifested in the fact that the main petal splits into two or even three petals, as well as in increasing the overall sharpness of the pattern.

Experimental and numerical study of acoustic pressure distribution in a sonochemical reactor

In this work, it is shown numerically in COMSOL Multiphysics and experimentally that a change in the NaCl concentration in water significantly affects the distribution of acoustic pressure in a laboratory sonochemical reactor. Thus, in distilled water under the action of ultrasound, two areas of increased pressure were ob-served, one of which was located directly above the ultrasound source, and the second was near the surface of the liquid, this effect is associated with the reflection of sound waves from the surface of the liquid. With the increase in the salt content, the maximum value of the acoustic pressure in the liquid decreases, which is associated with the dependence of the acoustic impedance of the liquid on the salt concentration and the peculiarities of the dynamics of vapor-gas bubbles in such solutions.

Effects of volume fraction and diameter of hollow spheres on acoustic properties of Metallic-Hollow-Sphere/Polyurethane (MHSP) acoustic composites

Metallic hollow spheres and polyurethane resin are excellent sound insulation and sound absorption materials. In this study, the surface modified 316L stainless steel hollow spheres were added into polyurethane by casting method. The influence of the volume fraction and diameter of the hollow spheres on the sound insulation and sound absorption performance of the Metallic-Hollow-Sphere/Polyurethane (MHSP) acoustic composites was investigated by impedance tube method and the relevant acoustic mechanism was discussed. When the volume fraction of hollow spheres is 45% and the diameter is 2.5 mm, composite has the best sound insulation performance. And when the volume fraction of hollow spheres is 60% and the diameter is 2.5 mm, composite has the best sound absorption performance. Due to the mass effect, damping effect, change of acoustic impedance and multiple interface of composites, sound waves will reflect, refract and scatter many times in the process of propagation, thus losing lots of sound energy to improve the sound insulation performance. The sound absorption mechanism of MHSP is that the friction, viscosity and reflection of sound waves in the pores of polyurethane, cavities of the hollow spheres and interfaces will cause the loss of sound energy and turn it into heat energy.

Reflection and refraction of a plane sound wave in an elastic plate with an inhomogeneous anisotropic coating

In paper the problem of the reflection and refraction of a plane harmonic sound wave by a homogeneous isotropic elastic plate with an continuously inhomogeneous anisotropic elastic coating is considered. It is assumed that the plate is adjoin to ideal fluids. The propagation of small perturbations in a ideal fluid in the case of steady state oscillations is described by Helmholtz’s equation. The propagation of elastic waves in a uniform isotropic elastic plate is described by scalar and vector Helmholtz’s equations for longitudinal and transverse waves. Oscillations of an inhomogeneous anisotropic elastic coating are described by general motion equations of the continuous medium. The boundary-value problem for the system of ordinary second order differential equations is constructed for determination of the displacement field in inhomogeneous anisotropic coating. An analytical description of the reflected and transmitted through the plate acoustic fields is obtained. Particular cases when the material of an inhomogeneous coating is transversely isotropic and isotropic are considered. The results of numerical calculations of dependence of reflection coefficient of a homogeneous isotropic plate with a transversely isotropic coating from the incidence angle of plane wave are presented.

Broadband low-frequency sound insulation performance of quasi-zero stiffness local resonant acoustic metamaterial plate

For realizing the effective broadband insulation of sound at low frequencies, a novel local resonant acoustic metamaterial plate having quasi-zero stiffness is proposed. Based on the classical mass-spring local resonance model, a metastructure is constructed by introducing additional inclined springs with negative stiffness. First, the normalized equivalent stiffness of the quasi-zero stiffness structure is derived from the perspective of dynamics. Then, by employing the method of equivalent medium, a sound insulation model of the metastructure is established theoretically. For validation, numerical simulations as well as experimental measurements are carried out. It is demonstrated that in the positive (equivalent) stiffness regime, increasing either the stiffness ratio or pre-compression can significantly reduce the local resonance frequency of the metastructure, which exhibits the great insulation performance around the local resonance frequency. For a typical example, the proposed metastructure can achieve a transmission loss of 30 dB around 10 Hz. In contrast, within the negative stiffness regime, the metastructure does not exhibit local resonance, thus avoiding sound insulation valley caused by the “coincidence effect”. Compared with traditional materials or similar metamaterials, the proposed metastructure has significant advantages in sound insulation (e.g. more than 30 dB drop over a wide frequency band of 53－1500 Hz). By analyzing the equivalent mass density, reflection coefficient, and acoustic impedance ratio of the metastructure, the physical mechanism behind its superior insulation performance is further explored. The equivalent mass density changes from positive to negative and tends to infinity at the insulation peak. The insulation peak is attributed to a nearly perfect total reflection of sound wave caused by impedance mismatch, while the insulation valley is caused by low-frequency “coincidence effect” originating from the local resonance band gap. The using of the quasi-zero stiffness local resonance to achieve low-frequency broadband sound insulation overcomes the disadvantages of traditional metamaterials such as reduced stiffness or additional mass, thus becoming vastly attractive for constructing low-frequency broad band sound insulation structures.

Reflection of acoustic waves from a bubble screen in water with hydrate bubbles

Dynamics of acoustic signal passing through a bubble screen is investigated. The case when the gas inside the methane bubbles is in hydrate formation conditions is considered. Influence of the hydrate formation process, the initial radius of bubbles and the gas content on the value of the attenuation coefficient and the phase velocity of wave propagating through the deep-sea bubble screen have been studied. Coefficients of reflection and passage of sound waves are obtained at boundaries separating areas of single-phase and two-phase zones. It has been found that the hydrate formation process increases the wave attenuation coefficient by more than two orders of magnitude in the low frequency area (less than 1 kHz).

Design, fabrication and sound absorption performance investigation of porous copper fiber sintered sheets with rough surface

A novel porous copper fiber sintered sheets (PCFSSs) with different porosities were fabricated using the cutting copper fibers with rough surface. The effect of fiber surface morphology, porosity, thickness and gradient pore structure of PCFSS on sound absorption performance was tested by using the transfer function method. Our results show that the copper fiber sintered sheets with rough surface exhibited better sound absorption performance compared with the copper fiber sintered sheets with smooth surface. The increase of sound resistance by increasing thickness or decreasing porosity could significantly improve the sound absorption coefficients in the low frequency region and widen its acoustic absorption bandwidth. Whereas, the sound absorption performance in the high frequency region was decreased with the increase of sound resistance. Moreover, the three-layer PCFSSs with gradient pore structure could cause a repeated propagation and dissipation due to the reflection of sound waves between the gradient interfaces, which can satisfy the requirements of noise control in different frequency region. Our work provides a method for improving sound absorption performance of porous metal material for different applications.

Enhanced sound insulation properties of microporous PMMA foams by constructing novel multilayered and directional cell structure (MDCS)

AbstractThe main purpose of this study is to improve the performance of soundproofing materials through structure design without any functional phases. The sound insulation properties of PMMA microporous foams with multilayered and directional cell structure (MDCS) were investigated. The influence of the MDCS on sound transmission loss was discussed in detail. In addition, the mechanism for improving the sound transmission loss of the multilayered foams was discussed. The results show that the sound transmission loss value of the multilayered foams is up to 29.70 dB, which is 29.5% higher than that of the single‐layer foams. It is due to the MDCS, which reduces the cell size of the foams, leading to increase the reflection and scattering of sound waves in pores. Meanwhile, the MDCS accompanied by multilayer interfaces increases the multiple reflection of sound waves at the interfaces. Besides, the smaller cell size and higher cell density strengthen the stiffness of the foams, which promotes the sound insulation properties. This study presents a novel and convenient method to design modern sound insulation materials.

Free and forced bending vibrations of a thin plate in a perfect compressible fluid with energy dissipation taken into account

AbstractA refined statement of stationary dynamic acoustoelasticity problems of thin isotropic plates surrounded from both sides by acoustic media assumed to be perfect compressible fluids has been studed. The problem statement takes into account the energy dissipation in the material of the plate and fluid on the basis of the Kelvin‐Voigt hysteresis model. The refinement of the fluid behavior is based on the assumption that the pressure increment is proportional not only to volumetric strain, but also to the rate of its volumetric strain. This assumption allows us to obtain the generalized Helmholtz wave equation by introducing Skudrzyk's complex sound velocity into consideration to take account of the energy dissipation. The motion equations of the plate are based on the classical Kirchhoff‐Love model and are obtained in two versions. In the first version unsimplified three‐dimensional wave equations are used to determine the aerohydrodynamic load acting on a plate. The second version is based on simplifying the equations of fluid motion by the introduction of the well‐known hypothesis of plane reflection and emission of sound waves. On the basis of the derived equations, exact analytical solutions of two types of problems are obtained. The first type is related to the problem of free vibrations of a rectangular plate hinged around the contour when complex eigenfrequencies were defined. The second type is related to the problem of forced vibrations of the plate under the action of a flat mono‐harmonic incident sound wave when sound transmission loss, the stress‐strain state parameters of the plate as well as the laws of change in sound pressure in a fluid were determined. It is shown that correct and more meaningful solutions of acoustoelasticity problems of the considered class are possible only in case of describing the behavior of a fluid with unsimplified three‐dimensional wave equations with consideration of the energy dissipation.

A Tool Detects Violation Of Road Markings Using Ultrasonic Sensors Based On Internet Of Things

In our daily lives, of course we often see the number of motorbike or car vehicles that do not care about the traffic lights, even though the traffic is red, but there are always vehicles that stop or even slightly cross the white line that is specifically for pedestrians so that can pass when the traffic lights are red. Ultrasonic sensors work based on the principle of reflection of sound waves, where these sensors produce sound waves which then capture it again with a time difference as the basis for sensing. After analyzing the needs, the author will build a Tool to Detect Road Marking Violations Using the Internet-Based Ultrasonic Sensor on the grounds that all the components needed in building the tool already exist. Which is where the driver will be exposed to a photo if it crosses the marking line that has been provided on the highway. Because the concept of the internet of things involves tools with users to communicate. The composition of the algorithm, the author uses python which has become the default programming language raspbian operating system. Algortihm construction in the tool is a red light algorithm, an ultrasonic sensor algorithm, an image capture algorithm, and an algorithm for sending text and images via email. Traffic officers will be facilitated because the tool is in accordance with the traffic light seconds, can take pictures, and also officers are informed in the form of text and images.

Evaluation of Mixed Deep Neural Networks for Reverberant Speech Enhancement.

Speech signals are degraded in real-life environments, as a product of background noise or other factors. The processing of such signals for voice recognition and voice analysis systems presents important challenges. One of the conditions that make adverse quality difficult to handle in those systems is reverberation, produced by sound wave reflections that travel from the source to the microphone in multiple directions. To enhance signals in such adverse conditions, several deep learning-based methods have been proposed and proven to be effective. Recently, recurrent neural networks, especially those with long short-term memory (LSTM), have presented surprising results in tasks related to time-dependent processing of signals, such as speech. One of the most challenging aspects of LSTM networks is the high computational cost of the training procedure, which has limited extended experimentation in several cases. In this work, we present a proposal to evaluate the hybrid models of neural networks to learn different reverberation conditions without any previous information. The results show that some combinations of LSTM and perceptron layers produce good results in comparison to those from pure LSTM networks, given a fixed number of layers. The evaluation was made based on quality measurements of the signal’s spectrum, the training time of the networks, and statistical validation of results. In total, 120 artificial neural networks of eight different types were trained and compared. The results help to affirm the fact that hybrid networks represent an important solution for speech signal enhancement, given that reduction in training time is on the order of 30%, in processes that can normally take several days or weeks, depending on the amount of data. The results also present advantages in efficiency, but without a significant drop in quality.

What our prehistoric ancestors can teach us about echoing soundscapes that is relevant to modern noise studies

Results of archaeoacoustic studies are applied to outdoor entertainment noise investigations. When considering impacts of noise in modern urban environments, it is well to consider the evidence left by our ancestors regarding the influence of reflective sound surfaces, as well as cultural perceptions of the sounds themselves. Acoustic research into the placement of global prehistoric rock art has revealed that our ancestors selectively chose echoing environments to produce cave paintings and canyon petroglyphs. Furthermore, those images depicted often match descriptions of echo spirits contained in ancient echo myths from around the world. The cultural perception of echoes was that these “extra” sounds were considered mysterious answers from sacred beings worthy of worship—the same phenomena that today are understood as sound wave reflections and considered annoying. Implications for modern noise investigations are discussed. Measure not just noise source amplitude, but consider also the effect of reflective urban structures to multiply, distort and overlap noises, sometimes acting as whisper galleries to cause sound to carry far down “urban canyons.” Also, relative to perception, a given dB level can affect different listeners in different ways, e.g., certain music perceived as entertaining to some may be perceived as unpleasantly disturbing to others.

Reflection and refraction of sound waves on a smooth and the non-flat boundary between two liquids

The problem of the scattering of sound waves by the boundary between two liquids has an elementary solution in a case of flat boundary and can be reduced to a solution of an integral equation with the singular oscillating kernel. In practical applications, wast majority of boundaries are treated as random surfaces and approximate methods produce only some statistical moments of the sound field. When the boundary is smooth and non-flat there is no simple method which can produce physically consistent results. This work presents an approach, which exploits a smoothness of the boundary to build an orthogonal coordinate system and rewrite wave equations at both sides of the surface in this system. For a given incident field of sound pressure and particles velocities by satisfying the boundary conditions and applying the split-step method and FFT we build a reflected and refracted field of sound pressure and particles velocity in both media, producing physically reliable interference patterns.The problem of the scattering of sound waves by the boundary between two liquids has an elementary solution in a case of flat boundary and can be reduced to a solution of an integral equation with the singular oscillating kernel. In practical applications, wast majority of boundaries are treated as random surfaces and approximate methods produce only some statistical moments of the sound field. When the boundary is smooth and non-flat there is no simple method which can produce physically consistent results. This work presents an approach, which exploits a smoothness of the boundary to build an orthogonal coordinate system and rewrite wave equations at both sides of the surface in this system. For a given incident field of sound pressure and particles velocities by satisfying the boundary conditions and applying the split-step method and FFT we build a reflected and refracted field of sound pressure and particles velocity in both media, producing physically reliable interference patterns.