Sound Wave Traveling Research Articles

Autonomous Technology for 2.1 Channel Audio Systems

During the COVID-19 pandemic, smart home requirements have shifted toward entertainment at home. The purpose of this research project was therefore to develop a robotic audio system for home automation. High-end audio systems normally refer to multichannel home theaters. Although multichannel audio systems enable people to enjoy surround sound as they do at the cinema, stereo audio systems have been popularly used since the 1980s. The major shortcoming of a stereo audio system is its narrow listening area. If listeners are out of the area, the system has difficulty providing a stable sound field. This is because of the head-shadow effect blocking the high-frequency sound. The proposed system, by integrating computer vision and robotics, can track the head movement of a user and adjust the directions of loudspeakers, thereby helping the sound wave travel through the air. Unlike previous studies, in which only a diminutive scenario was built, in this work, the idea was applied to a commercial 2.1 audio system, and listening tests were conducted. The theory and the simulation coincide with the experimental results. The approximate rate of audio quality improvement is 31%. The experimental results are encouraging, especially for high-pitched music.

Layer-Averaged Water Temperature Sensing in a Lake by Acoustic Tomography with a Focus on the Inversion Stratification Mechanism.

Continuous sensing of water parameters is of great importance to fluid dynamic progress study in oceans, coastal areas and inland waters. The acoustic tomography technique can perform water temperature field measurements horizontally and vertically using sound wave travel information. The layer-averaged water temperature can also be measured with the acoustic tomography method. However, investigations focusing on the stratified mechanism, which consists of stratification form and its influence on inversion error, are seldom performed. In this study, an acoustic tomography experiment was carried out in a reservoir along two vertical slices to observe the layer-averaged water temperature. Specifically, multi-path sound travel information is identified through ray tracing using high-precision topography data obtained via a ship-mounted ADCP during the experiment. Vertical slices between sound stations are divided into different layers to study layer division inversion methods in different preset types. The inversion method is used to calculate the average water temperature and inversion temperature error of every layer. Different layer methods are studied with a comparison of results. The layer division principle studied in this paper can be used for layer-averaged water temperature sensing with multi-path sound transmission information.

A Blind Stick Assisting Blind Person to Detect Obstacle Ahead and to Alert the User

In today's world where man has reached Mars, technology is helping them grow stronger with time. Normal persons get the most advantage but the disabled are also not left much behind. Today there are advancements for the disabled persons too. This study has dealt with making a blind stick which will assist a visually blind person to detect the possible obstacles ahead and to alert the user timely.The system consists of a micro-controller, a buzzer and four sensors, namely ultrasonic sensor, !ame sensor, water sensor and LDR. All the sensors collect value and send it to the micro-controller. The ultrasonic sensor triggers a pulse for 10 micro seconds and then reads the sound wave travel time in microseconds to the Arduino-Nano. Using this time, it calculates the distance of any obstacle if present in front. When no obstacle is found within 1.4m range, it keeps on beeping normally, but as soon the obstacle crosses the limit and the user approaches close to it, it starts beeping faster. Similarly, the re sensor reads of re is present ahead. When encountered it reads the reading through the IR sensor and the value is then compared to a reference value set. If found more that means it can be dangerous and thus alerts the user. Similarly, the water sensor receives value from sensor and when senses danger comparing the value alerts the user.The developed prototype was made using simple things and turns out under the cost of Rs.300/- thus making it highly affordable.

A Fiber Optic Ultrasonic Sensing System for High Temperature Monitoring Using Optically Generated Ultrasonic Waves.

This paper presents the design, fabrication, and characterization of a novel fiber optic ultrasonic sensing system based on the photoacoustic (PA) ultrasound generation principle and Fabry-Perot interferometer principle for high temperature monitoring applications. The velocity of a sound wave traveling in a medium is proportional to the medium’s temperature. The fiber optic ultrasonic sensing system was applied to measure the change of the velocity of sound. A fiber optic ultrasonic generator and a Fabry-Perot fiber sensor were used as the signal generator and receiver, respectively. A carbon black-polydimethylsiloxane (PDMS) material was utilized as the photoacoustic material for the fiber optic ultrasonic generator. Two tests were performed. The system verification test proves the ultrasound sensing capability. The high temperature test validates the high temperature measurement capability. The sensing system survived 700 °C. It successfully detects the ultrasonic signal and got the temperature measurements. The test results agreed with the reference sensor data. Two potential industry applications of fiber optic ultrasonic sensing system are, it could serve as an acoustic pyrometer for temperature field monitoring in an industrial combustion facility, and it could be used for exhaust gas temperature monitoring for a turbine engine.

Quasi real time monitoring system for the tomographic reconstruction of the vortex wind field

Quasi real time vortex wind field monitoring system for the tomographic reconstruction of the vortex wind velocity field was developed. The system was implemented by installing the multichannel sound transmitter and receiver pairs on both sides of the monitoring area. Sound wave travel time data were measured between the arbitrary combination of the facing transmitters and receivers. To speed up the multichannel data collection time, transmission and reception was made in parallel by sending the coded modulation signals. The demodulation correlation calculation, for the extraction of the desired data from the multiple transmission signals, was made in high speed by using GPU (Graphics Processing Unit). Test examination, using the four channel indoor system, showed the promise to complete the vortex wind velocity image production about every 1 s.

Accurate sound source localization in a reverberant environment using multiple acoustic sensors

This paper introduces a new method for the estimation of sound source distance and direction using at least three microphone sensors in indoor environments. Unlike the other methods that normally use approximations in obtaining the time difference between sensors, this method exploits the existed geometrical relationships of the sensors to form an exact solution to estimating the source position. To overcome reverberation, an enhancing pre-process has been used for different sound sources with different spectra, e.g., single frequency, multiple frequencies and different noise shapes. Source direction and distances are estimated from time of sound wave travel and distances of acoustic sensors. Using the method described in this paper a level of 1° accuracy is obtained. Several experimental tests have been undertaken that verify the results. Conclusions and future work are also described.

Acoustic analog to quantum mechanical level splitting

A simple physical system is discussed that mirrors the quantum mechanical infinite square well with a central delta well potential. The physical realization consists of a continuous sound wave traveling in a pair of tubes separated by an adjustable diaphragm. The equivalence between the quantum system and the acoustic system is explored. The analytic solution to the quantum system exhibits level splitting as does the acoustic system.

A theoretical study of duct noise control by flexible panels

Theoretical exploration is undertaken for passive noise control by flush-mounted panels in an otherwise rigid duct. For a plane sound wave traveling in the flexible segment, the wall compliance renders a wave speed less than the isentropic speed of sound in air. Scattering and reflection occur at the upstream edge of the panel while the energy flux of the transmitted wave is partitioned between the wall flexural waves and the sound in air. For a lossless panel these waves are scattered and reflected again by the downstream edge forming standing waves responsible for the undesirable passbands. For panels with substantial structural damping, however, both flexural and sound waves diminish with distance, eliminating the passbands. It is estimated that the wave dissipation by panel materials like rubber could outperform typical fibrous duct lining. The combination of wave reflection, dissipation, and slowing down allows broadband, low-frequency noise reduction over a short distance.

Passive muffler for low pass frequencies

This invention relates to sound attenuating mufflers, and more particularly to sound attenuating mufflers for dampening sound waves of various frequencies above a pre-selected cut-off frequency. Specially positioned acoustical insulation is provided to partially attenuate sound waves of a relatively low frequency. The insulation is carried in a chamber having one dimension of sound wave travel on the order of one-tenth the wavelength of a preselected cutoff frequency above which sound attenuation is desired. An adjacent chamber substantially free of insulation has one dimension of sound wave travel on the order of one-quarter wavelength of the cutoff frequency.

Cetacean perception of the marine environment−A theoretical approach

The possibility exists that cetaceans can assess undersea environment through their sensing the modification of their probe signals in terms of harmonic content as well as the intensity of the reflected signals. The fluidic constitutivity or the elasticity (or a combination thereof) of the impinged surrounding objects affect the cetaceans’ probe signals so that additional harmonics appear in specific ways in the reflections. Absorptivity, spatial distribution, and the distance and acoustic impedance between the emitter and the reflector constitute the other factors that affect the probe signals. The harmonics aspect of this theory derives from previous work in the study of sound propagation through rheological fluids [D. R. Raichel and W. H. Kapfer, J. Appl. Mech. (Ser. E) 40, 1–6 (1973); M. Sokolov, ibid. 41, 823–825 (1974)], whereby perturbation techniques are applied to acoustic equations to yield the higher harmonics that result spontaneously from the inherent nonlinearity of sound wave travel through a constitutively real medium.

Directional hydrophone suitable for flush mounting

A substantially flat and disc-like shaped sound transducer for sensing sound waves in a fluid transmission medium and having directional and omnidirectional response characteristics to the sound waves. The sound transducer having a circular vibratile plate divided into quadrantal portions and having a surface adapted to be coupled to the transmission medium for providing sound wave motion in the portions dependent upon, and in response to, sound wave travel in the transmission medium and having a plurality of electroacoustic transducer elements coupled to the quadrantal portions of the vibratile plate for providing electrical output signals in response to the wave motions in diametrically opposed quadrantal portions. The sound transducer responding to incident sound waves having wavefront travel directions, in the transmission medium, substantially parallel to the coupled surface. The relatively flat physical configuration of the sound transducer makes it especially suited for flush mounting in a surrounding surface, such as the hull of a ship or submarine.

Correlation between young's modulus and thermal properties of metallic glasses

The effect of glass formers, P and B, on the Young's modulus of a number of metal-metalloid glasses are reported. Young's modulus and glass temperature of inter-transition metal glasses, Nb--Ni and Zr--Cu, are presented. Elastic constants of the metallic glasses correlate somewhat to atomic ordering. The Young's moduli were obtained by measuring the transit time of a 100 kHz Young's modulus sound wave traveling in the sample.

On the velocity of a rigid sphere in a sound wave

A study is presented of the oscillatory motion of a rigid sphere that is induced by a plane, monochromatic sound wave traveling in a viscous, non-heat-conducting fluid of infinite extent. Results for the sphere's velocity amplitude and phase, relative to those of the fluid, are obtained for sound waves of arbitrary frequency. These reduce to those predicted by irrotational flow theory, and to those obtained from viscous, incompressible, unsteady flow theory. It is found that, in general, the range of applicability of either extreme case is quite limited. However, when the ratio of the viscous diffusion velocity, √ων, to the speed of sound, c 0, is small, it is found that the two limiting forms agree well with the general results presented here within wide ranges which overlap in the vicinity of kR = 1, where k is the wave number and R is the sphere radius. Thus, the viscous results are applicable for kR ⩽ 1, whereas the inviscid ones apply for kR ⩾ 1.

The integral representation of fractionally exponential functions and their application to dynamic problems of linear visco-elasticity

Fractionally exponential functions are written in the integral form and distribution functions with an Abelian singularity are obtained for the corresponding relaxation and retardation spectra. A principle is stated, defining the dynamic problems for which weakly singular functions can be used as the kernels of the integral operators. A one-dimensional sound wave traveling in a semiinfinite visco-elastic medium is considered. The generalized exponential functions of fractional order, proposed by Yu. N. Rabotnov [1, 2] as the kernels of Boltzmann-Volterra integral relations, have found wide applications in theory of linear visco-elasticity. This is explained partly by the great mathematical flexibility of the F-operators when applying the Volterra principle to the solution of elastically hereditary problems and partly by the fact that almost all weakly singular kernels possessing an Abelian singularity are connected in some way or other with the F-functions. For example, the resolvent of the elementary weakly singular Abelian kernel is an F-function. The product of an exponential function with an Abelian kernel represents a particular case of the product of two F-functions with different fractional parameters, while the resolvent of such a kernel is the product of an exponential function with an F-function [3, 4]. Since the e-functions are defined by slowly convergent series, their various asymptotic forms [2, 5–8] are commonly used in practical calculations. The theory of F-functions can be developed further in the context of their integral representations, which enables a more exact physical interpretation to be given to their parameters and on occasion simplifies computational operations.

Effect of Radiative Transfer on a Sound Wave Traveling in a Gas having γ near One

It is shown that the assumption of specific heat ratio near one simplifies the analysis of plane sound waves subject to energy addition dependent on temperature, and in the case of radiative energy exchange in a fairly transparent gas, a third-order differential equation is obtained. Analytical solutions for a hot and a cool gas are presented which give the complete history of velocity and temperature profiles when a wave is produced by an impulsively started piston, with either a black or reflecting face. In a very hot gas, an optically thin wave which is thermally dominated by the piston face (or the undisturbed gas, if the face is perfectly reflecting) disperses as though by relaxation and is followed by an optically thick wave, which is thermally independent of the piston and disperses as though by conduction. Transition between thin and thick waves is accomplished in a temperature boundary layer. In a cool gas, dispersion occurs as though by simple radiative heat conduction. Finally, it is remarked that dispersion in a transparent gas would be observed on the scale of a meter only if the gas is very hot.

High-Intensity Sound and Shock Waves

High-intensity sound, or macrosonics, differs from ordinary sound in its manner of propagation. All parts of an ordinary sound wave travel with the same speed (the sound speed). However, in high-intensity sound the pressure maxima travel faster than the pressure minima. Consequently, high-intensity sound waves become distorted as they travel. This distortion may become so extreme that a discontinuity or shock wave develops when a maximum tries to overtake a minimum. Such a shock wave will start out very weak but will grow in size and then, perhaps, decay again. All of these effects are illustrated by the example of a piston moving periodically at one end of a semi-infinite tube. The free vibration of the gas in a closed tube is also examined and found to be modified by the foregoing effects. Similarly the sound waves produced by a piston at one end of a closed tube are found to be affected, in some cases shocks developing and in other cases the wave forms merely being distorted. Similar phenomena occur in three dimensions, as can be seen from a new theory of the propagation of high-intensity sound in three dimensions. This theory includes a new phenomenon, the possibility of refraction caused by intensity variations on a wave front. It also leads to shock formation in certain cases, and describes the way in which the shocks propagate, grow, and decay. The theory is an extension of a previous theory of weak shocks which was called geometrical acoustics. It too is a geometrical theory.