### ASA 125th Meeting Ottawa 1993 May

## 2aNS2. Acoustical applications of wavelets: Audio coding and sonar.

**Ahmed H. Tewfik
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*Dept. of Elec. Eng., Univ. of Minnesota, Minneapolis, MN 55455
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Wavelets are a family of basis functions for the space of finite energy
signals. In a wavelet decomposition, a signal is expanded in terms of
translates and dilates of a single function. Wavelets provide a flexible
decomposition of signals. This flexibility is the foundation of a new
generation of advanced low-bit-rate, high-quality audio coding procedures. By
adaptively choosing the wavelet representations of consecutive segments of the
audio signal one can optimally exploit the masking effect in human hearing. The
performance of the resulting coding techniques surpasses that of known
nonwavelet-based approaches. Another important property of wavelet
decompositions is the fact that one can relate the structure of the wavelet
coefficients of a given signal to the local time and frequency domain
characteristics of the signal. In sonar processing, this fact has been
exploited by a new class of robust direction of arrival estimation algorithms
that can deal with background correlated noise of an unknown correlation
structure. These algorithms separate signal from noise by analyzing the
structure of the wavelet coefficients of the array outputs.