ASA 124th Meeting New Orleans 1992 October

5pPA9. Vein diagram: A simplified version of time-frequency display for acoustic structure response.

Nai-chyuan Yen

Louis R. Dragonette

Phys. Acoust. Branch, Naval Res. Lab., Washington, DC 20375-5320

Christopher A. Ross

SFA, Inc., Landover, MD 20785

The application of time and frequency displays to depict the wave packet components of the acoustic response from a submerged object is a useful analysis tool in the study of scattering phenomena. However, such representations are generally obtained from processing algorithms that rely on some controlled parameters (special windows or shading kernals), which may not provide correct interpretations of scattering physics. The technique considered here places emphasis on the correlation property of the structure's response and expresses it in terms of the conventional ambiguity function. The vein diagram sums up the reduced highlights from a 2-D Fourier transform of this ambiguity function. To focus on the essential wave packet components, the technique allows flexibility in the choice of windows and an adjustable feature selection threshold. Because the vein diagram is derived from the energy distribution of the structure's response, it provides a more concise and meaningful association with the physics of wave packet formation. Implementation of our processing technique in a graphics working station (IRIS) will be described, and its relationship to other well-known processing methods such as the Wigner distribution function, Gabor transform, and wavelet decomposition will be described.