Range compensation for backscattering measurements in the difference-frequency nearfield of a parametric sonar

Thumbnail Image
Date
2012-05
Authors
Foote, Kenneth G.
Linked Authors
Alternative Title
Date Created
Location
DOI
10.1121/1.3688505
Related Materials
Replaces
Replaced By
Keywords
Acoustic wave scattering
Backscatter
Biological techniques
Sonar signal processing
Underwater acoustic propagation
Zoology
Abstract
Measurement of acoustic backscattering properties of targets requires removal of the range dependence of echoes. This process is called range compensation. For conventional sonars making measurements in the transducer farfield, the compensation removes effects of geometrical spreading and absorption. For parametric sonars consisting of a parametric acoustic transmitter and a conventional-sonar receiver, two additional range dependences require compensation when making measurements in the nonlinearly generated difference-frequency nearfield: an apparently increasing source level and a changing beamwidth. General expressions are derived for range compensation functions in the difference-frequency nearfield of parametric sonars. These are evaluated numerically for a parametric sonar whose difference-frequency band, effectively 1–6 kHz, is being used to observe Atlantic herring (Clupea harengus) in situ. Range compensation functions for this sonar are compared with corresponding functions for conventional sonars for the cases of single and multiple scatterers. Dependences of these range compensation functions on the parametric sonar transducer shape, size, acoustic power density, and hydrography are investigated. Parametric range compensation functions, when applied with calibration data, will enable difference-frequency echoes to be expressed in physical units of volume backscattering, and backscattering spectra, including fish-swimbladder-resonances, to be analyzed.
Description
Author Posting. © Acoustical Society of America, 2012. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 131 (2012): 3698-3709, doi:10.1121/1.3688505.
Embargo Date
Citation
Journal of the Acoustical Society of America 131 (2012): 3698-3709
Cruises
Cruise ID
Cruise DOI
Vessel Name