Multiple Angle Acoustics

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Contents
Project Goal	Specifications	People
Development Pictures/Movies/Data	Sponsors	Links
Publications

Project Goal
The multiple angle acoustics project is focused on applying sound scattering measurements made at multiple angles in order to estimate biophysical parameters of marine animals such as size, shape, orientation, and taxa. This is an emerging area of bioacoustics which departs from the more traditional backscatter paradigm in an effort to improve the specificity of acoustic systems beyond remote sensing of volume backscatter.

There are two major components to this research. The first, is the construction and evaluation of a multiple angle scattering apparatus, while the second is the development of algorithms for learning how to relate the multiple angle acoustic scatter to important bio-physical parameters. The laboratory setting allows us to compare the estimates produced by the algorithms to video data of the scatters during insonification. This provides a method for characterizing the performance of the system on live subjects.

General Specifications
The multiple angle scattering apparatus is composed of a variety of acoustical and optical imaging systems. A technical sketch of the system shows the major components and their relative location in the observation tank. The system is made up of a transducer array, a large (14x10x8ft) chilled seawater tank, two high sensitivity video cameras on adjustable pan and tilt mounts, and a rigid frame to hold everything together inside the tank.

A single transducer is used as the source of sound, while the other elements of the array receive only. This multistatic configuration allows for multiple angles of scatter to be acquired simultaneously. The stereo video system allows us to infer the size, shape, orientation, and taxa of the scatterer during insonification.

The system is powered by two computers running Windows XP, one using LabVIEW and the other using the Matrox Imaging Library. Panametrics broadband preamps are used for signal enhancement prior to digitization. An ENI AP400B power amplifier to used to power the sound source.
Detailed Specifications

People

Principal Investigators	Dr. Jules S. Jaffe
Graduate Students	Paul L. D. Roberts
Development Support	Marine Science Development Shop
Technical Consultants	Robert Glatts Benjamin Maurer Fernando Simonet Eddie Kisfaludy

Development Pictures/Movies/Data
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Pictures

Scattering Apparatus

Data

Sponsors

California Sea Grant

Publications

Jaffe, J. S. "Using multi-angle scattered sound to size fish swimbladders, ICES Journal of Marine Science 63 (8) 1397-1404 SEP 2006

Roberts, P. L. D. and Jaffe, J. S. "Multiple angle acoustic classification of zooplankton, J. Acoust. Soc. Am. 121 (4): pp. 2060-2070, 2007 Apr.