Related Experiment Videos
Target phase: an extra dimension for fish and plankton target identification.
1National Institute of Water and Atmospheric Research, Private Bag 14-901, Kilbirnie, Wellington, New Zealand. r.barr@clear.net.nz
The Journal of the Acoustical Society of America
|October 26, 2005
Summary
Analyzing fish acoustics, this study reveals that the phase of backscattered signals, not just magnitude, provides valuable species identification information. Compensating for water propagation effects highlights unique phase signatures for fish targets.
Area of Science:
- Acoustics
- Bioacoustics
- Fish Biology
Background:
- Fish identification commonly relies on acoustic backscatter magnitude.
- The phase information in acoustic backscatter from fish remains largely underutilized.
- Residual phase signatures, after compensating for propagation, offer target-specific insights.
Purpose of the Study:
- To explore the utility of acoustic backscatter phase for fish target characterization.
- To model acoustic backscatter in complex target space using a Monte Carlo technique.
- To explain in situ observations of fish targets using physical modeling.
Main Methods:
- Compensating for gross phase changes due to water propagation.
- Estimating the rate of echo phase change relative to the transmitted pulse.
- Computing acoustic backscatter in complex target space for model fish targets (with/without swimbladders).
Main Results:
- Residual phase signatures contain useful target-specific information.
- Clear grouping of fish targets observed in complex target space (target strength vs. phase change rate).
- Modeled acoustic backscatter features align with in situ data, explained by fish size and attitude.
Conclusions:
- The phase of acoustic backscatter is a valuable, underused feature for fish identification.
- Complex target space analysis, incorporating phase, enhances fish target strength analysis.
- The complex target approach is broadly applicable to fish acoustics, independent of frequency.