A technique for calibration of monostatic echosounder systems

• Published in: IEEE journal of oceanic engineering Vol. 21; no. 3; pp. 298 - 305
• Main Authors: Vagle, S., Foote, K.G., Trevorrow, M.V., Farmer, D.M.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.07.1996; Institute of Electrical and Electronics Engineers
• Subjects: Acoustic beams; Acoustic transducers; Acoustics; Band pass filters; Brackish; Calibration; Cobalt; Exact sciences and technology; Frequency; Freshwater; Fundamental areas of phenomenology (including applications); Instruments; Manufacturing; Marine; Physics; Resonance; Transduction; acoustical devices for the generation and reproduction of sound; Tungsten; Underwater sound; Vertebrata; Pisces; Calibration; High frequency; Underwater acoustics; Zooplankton; Echo sounding
• ISSN: 0364-9059; 1558-1691
• DOI: 10.1109/48.508160

A calibration technique has been adapted to render complete system calibrations of high-frequency acoustical instrumentation. This is based on standard targets; specifically, precisely manufactured spheres composed of tungsten carbide with 6% cobalt binder. The use of multiple sphere sizes was found to be advantageous, both as an independent check of the calibrations, and so that resonances in the sphere responses at certain frequencies could be avoided. Complete system gains and beam patterns, which include effects of bandpass filters and finite-pulse lengths, were determined by moving the spheres individually in the transducer far-fields. Use of this procedure ensures control over the acoustical characteristics of transducers, which may change from the time of manufacture and first testing due, for example, to platform mounting. It also provides a direct means of measuring the sampling volume at relatively high and constant signal-to-noise ratios. Implementation of this technique is discussed using a multifrequency sonar system as an example.