An Analysis of Vibration Sensitivity in Hydrophone Design
Abstract
Hydrophones used in the ocean produce spurious outputs because of vibration sensitivity that can severely degrade measurement accuracy. Sources of these vibration inputs are ocean surface wave, flow turbulence, and induced nonacoustic mechanical vibration. The hydrophone response to these vibrations is a noise voltage output. This can lead to a signal-to-noise problem, particularly when measurements of small sound pressure levels are to be made. This report presents an analysis of the vibration responses of three typical piezoelectric hydrophone sensor elements configurations and gives design methods and constraints for reducing the problem of vibration sensitivity to an acceptable level. The sensor element configurations analyzed are the radially polarized cylindrical shell. The analysis is carried out for two effects. First an electromechanical analyses is given of the voltage sensitivity of each of the three sensor configurations to the inertial effect of acceleration inputs. The second effect analyzed is the voltage sensitivity of a pressure sensitive sensor element to the hydrostatic pressure amplitude caused by periodic vertical displacements of a hydrophone. Results of the first analyses show that the radially polarized cylindrical shell configuration have zero acceleration sensitivity to inputs on the axes of symmetry. The analysis for the second effect, hydrophone sensor response of periodic vertical displacements, show high voltage sensitivity to very small displacement amplitudes. Data are given for the maximum permissible vertical displacement amplitude to produce a 20-dB signal-to-noise ratio. Based on these analyses, design considerations are given to minimize hydrophone vibration sensitivity.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 28, 1980
- Accession Number
- ADA092809
Entities
People
- George D. Hugus Iii
Organizations
- United States Naval Research Laboratory