Remote Localization of an Underground Acoustic Source by a PASSIVE Sonar System

Jarng, Soon Suck 대한원격탐사학회 1998 International Symposium on Remote Sensing Vol.14 No.1

The aim of the work described in this paper is to develop a complex underground acoustic system which detects and localizes the origin of an underground hammering sound using an array of hydrophones located about 100m underground. Three different methods for the sound localization will be presented, a time-delay method, a power-attenuation method and a hybrid method. In the time-delay method, the cross correlation of the signals received from the array of sensors is used to calculate the time delays between those signals. In the power-attenuation method, the powers of the received signals provide a measure of the distances of the source from the sensors. A new hybrid method has been developed for estimating the origin of the underground acoustic source by coupling both methods. The Nelder-Meade simplex search algorithm is then used to numerically estimate the position of the source in those methods. For each method the sound localization is carried out in three dimensions underground. The distance between the true and estimated origins of the source is in some cases less than 6m for a search area of radius 250m.

A Study about Underground Acoustic Exploration

Jarng, Soon-Suck,Park, Jong-An,Rhee, Kang-Hyeon CHOSUN UNIVERSITY 1997 Basic Science and Engineering Vol.1 No.2

It necessary to measur eattenuation coefficients of underground mediumistic materials for the purpose of underground exploration and/or underground material research. in order to find out the origin of the sound/vibration which is arbitrarily produced inside a demolished minefield or an underground tunnel, the attenuation coefficient of the underground elastic wave propagation should be known for the interest area. In the present study, elastic waves that were stimulated by hammering shocks inside an underground tunnel were remotely sensed, and attentiation coefficients of the shocked elastic wave were experimentally measured as a functio of distance. The procedure of experimental methods by means of a hydrophone is described in detail. underground impulse-like vibration is produced by hammering shocks with constant force at each different position inside the underground tunnel, and the resultant propagated elastic wave is measured by the hydrophone located at the bottom of a 108 M deep water tunnel. Attenuation coefficients of -0.0214 were measured.

PZT4 Sonar Shell transmitter Simulation Using a Coupled FE-BE Method

Jarng, Soon-Suck The Acoustical Society of Korea 1998 韓國音響學會誌 Vol.17 No.e1

This article describes the application of a coupled finite element-boundary element method to obtain the steady-state response of a sonar transducer. The sonar shell is simulated to be driven by electrical charges applied onto inner and outer surfaces of the shell. It is shown that at relatively low input frequency a beam pattern which is almost close to omnidirection can be obtained. The coupled FE-BE method is described in detail.

Voice Expression using a Cochlear Filter Model

Jarng, Soon-Suck The Acoustical Society of Korea 1996 韓國音響學會誌 Vol.15 No.e1

Speech sounds were practically applied to a cochlear filter which was simulated by an electrical transmission line. The amplitude of the basilar membrane displacement was calculated along the length of the cochlea in temporal response. And the envelope of the amplitude according to the length was arranged for each discrete time interval. The resulting time response of the speech sound was then displayed as a color image. Five vowels such as a, e, I, o, u were applied and their results were compared. The whole procedure of the visualization method of the speech sound using the cochlear filter is described in detail. The filter model response to voice is visualized by passing the voice through the cochlear filter model.

Optimal Design of Deep-water 30kHz Omnidirectional Sonar Transducer Using a Coupled FE-BEM

Jarng, Soon-Suck The Acoustical Society of Korea 1999 韓國音響學會誌 Vol.18 No.e4

Deep-water sonar transducers of FFR (Free Flooded Ring) type have been designed using a coupled FE-BEM. The proposed sonar transducers are composed of piezoelectric ceramic tubes and structural steel materials for simple fabrication. In order to have an omnidirectional beam pattern around 30kHz, a conic steel is placed below a piezoelectric tube or a steel disc is placed between two piezoelectric tubes. The dynamics of the sonar transducer is modelled in three dimensions and is analyzed with external electrical excitation conditions. Various results are available such as directivity patterns and transmitting voltage responses. The most optimal structure and dimensions of the steel material were calculated, so that the beam patterns of the sonar transducers had +/- 3dB omnidirectivity at 30kHz.

Binaural Directivity Pattern Simulation of the KEMAR Head Model with Two Twin Hearing Aid Microphones by Boundary Element Method

Jarng Soon Suck,Kwon You Jung,Lee Je Hyeong The Acoustical Society of Korea 2005 韓國音響學會誌 Vol.24 No.e3

Two twin microphones may produce particular patterns of binaural directivity by time delays between twin microphones. The boundary element method (BEM) was used for the simulation of the sound pressure field around the head model in order to quantify the acoustic head effect. The sound pressure onto the microphone was calculated by the BEM to an incident sound pressure. Then a planar directivity pattern was formed by four sound pressure signals from four microphones. The optimal binaural directivity pattern may be achieved by adjusting time delays at each frequency while maintaining the forward beam pattern is relatively bigger than the backward beam pattern.

Directivity Pattern Simulation of the Ears with Two Pairs' Hearing Aid Microphone Arrays by BEM

Jarng Soon Suck,Kwon You Jung The Acoustical Society of Korea 2005 韓國音響學會誌 Vol.24 No.e2

The noise reduction of the In-The-Ear (ITE) hearing aid (HA) can be achieved by arrays of microphones. Each of the right and the left ears was assumed to have two HA microphones. These arrays of HA microphones produce particular patterns of directivity by some time delay between two microphones. The directivity pattern geometrically increase the S/N ratio. The boundary element method (BEM) was used for the three dimensional simulation of the HA directivity pattern with the two pairs' microphone arrays. The separation between two microphones was fixed to 10 mm. The time delay between the two microphones was calculated to produce the most narrow directivity pattern in the fore front of the head. The variation of the time delay was examined in accordance with input frequencies. This numerical analysis may be then applied for the calculation of the time delay parameter of the digital hearing aid DSP chip.

SEM Observation for the Damage of Inner Hair Cell Stereocilia of Guinea Pig Cochlea after Loud Tone Exposure

Jarng Soon Suck The Acoustical Society of Korea 2005 韓國音響學會誌 Vol.24 No.e1

The inner hair cell stereocilia of the guinea pig cochlea was examined under a scanning electron microscope (SEM) after loud tone exposure onto the ear drum of the animal. Before and after guinea pigs were exposed to intensive and continuous tone such as 106 dB SPL in intensity, the functioning of the cochlea was monitored by N1-N2 audiograms. The structural damage of the stereocilia of inner hair cells (IHCs) and outer hair cells (OHCs) was examined using the SEM in x 1500 magnification. The comparison between the functional change of the cochlea and the structural damage of the IHC stereocilia is done by means of photographic observation. It can be shown that the functional change might be related to the structural damage of the IHC stereocilia after intensive acoustic trauma.

Exterior Acoustic Holography Reconstruction of a Tuning Fork Using Inverse Non-singular BEM

Jarng, Soon-Suck The Acoustical Society of Korea 2003 韓國音響學會誌 Vol.22 No.e1

Non-singular boundary element method (BEM) codes are developed in acoustics application. The BEM code is then used to calculate unknown boundary surface normal displacements and surface pressures from known exterior near field pressures. And then the calculated surface normal displacements and surface pressures are again applied to the BEM in forward in order to calculate reconstructed field pressures. The initial exterior near field pressures are very well agreed with the later reconstructed field pressures. Only the same number of boundary surface nodes (1178) are used for the initial exterior pressures which are at first calculated by Finite Element Method (FEM) and BEM. Pseudo-inverse technique is, used for the calculation of the unknown boundary surface normal displacements. The structural object is a tuning fork with 128.4 ㎐ resonant. The boundary element is a quadratic hexahedral element (eight nodes per element).

Active Linear Modeling of Cochlear Biomechanics Using Hspice

Jarng Soon Suck,Kwon You Jung The Acoustical Society of Korea 2005 韓國音響學會誌 Vol.24 No.e3

This paper shows one and two dimensional active linear modeling of cochlear biomechanics using Hspice. The advantage of the Hspice modeling is that the cochlear biomechanics may be implemented into an analog Ie chip. This paper explains in detail how to transform the physical cochlear biomechanics to the electrical circuit model and how to represent the circuit in Hspice code. There are some circuit design rules to make the Hspice code to be executed properly.