Acoustic sampling volume versus equivalent beam angle
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http://hdl.handle.net/11250/104384Utgivelsesdato
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Irnprovements in target strength measurement have shown the equivalent
beam angle (EBA) to be a worrisome source of error in echo integrator
surveys. The reason is that the EBA is generally defined as a purely
physical characteristic of the transducer. In fact, it depends on both
the beam pattern and the detectability of fish, hence target strength,
behaviour, and detection threshold. This is clearly seen through the
concept of acoustic sampling volume, which is herein defined explicitly
and evaluated numerically in several examples. In order to preserve the
EBA in the echo integration equation, the EBA is generalized. Several
methods for measuring this quantity in situ are described.