• The Journal of the Acoustical Society of Korea
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• v.23 no.1
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• pp.8-16
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• 2004

An inversion method is presented for the determination of the compressional wave speed, compressional wave attenuation, thickness of the sediment layer and density as a function of depth for a horizontally stratified ocean bottom. An experiment for estimating those properties was conducted in the shallow water of South Sea in Korea. In the experiment, a light bulb implosion and the propagating sound were measured using a VLA (vertical line array). As a method for estimating the geoacoustic properties, a coherent broadband matched field processing combined with Genetic Algorithm was employed. When a time-dependent signal is very short, the Fourier transform results are not accurate, since the frequency components are not locatable in time and the windowed Fourier transform is limited by the length of the window. However, it is possible to do this using the wavelet transform a transform that yields a time-frequency representation of a signal. In this study, this transform is used to identify and extract the acoustic components from multipath time series. The inversion is formulated as an optimization problem which maximizes the cost function defined as a normalized correlation between the measured and modeled signals in the wavelet transform coefficient vector. The experiments and procedures for deploying the light bulbs and the coherent broadband inversion method are described, and the estimated geoacoustic profile in the vicinity of the VLA site is presented.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.97-100
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• 2000

정합장처리(matched-field processing)는 실제 음향자료와 복제음장과의 공간 coherence를 이용한 음장의 역추정 방법이다. 광대역 스펙트럼을 가지는 음원의 경우 협대역 단일 주파수별로 정합장 출력을 계산한 후, 각 출력을 더하는 incoherent 광대역 정합장처리를 사용하였으나, 그 경우 수신기들과 주파수들간의 상호 공간과 주파수 정보를 사용치 못하므로 음원 위치추정 성능이 저하된다. 본 논문에서는 광대역 스펙트럼의 여러 주파수를 사용하여 확장된 CSDM(cross-spectral density matrix)을 구성하여 coherent 정합장처리를 구현하고, 각 정합장처리 기법에 대한 음원 위치추정 성능을 분석하였다.