Very accurate production oriented hydrophone calibration systems

Abstract

DED produces towed line sonar arrays for a large number of U.S. Navy applications. The fact that the performance of these arrays is very tightly specified and that DED produces hydrophones for these arrays by the tens of thousands each year has forced the development of production oriented hydrophone calibration systems meeting the following requirements: parameters measured—free field voltage sensitivity, relative phase; frequency range—1 Hz to 2 kHz; measurement repeatability—±0.2 dB max., ±0.5 dB degrees max.; measurement correlation with Navy's standard facility (NRL/USRD)—±0.2 dB max.; temperature/pressure—ambient. Automated measurement systems have been developed where the above hydrophone parameters are measured within closed, rigid air chambers. Measurements are made by comparison against acoustical standards which are built into each chamber. These systems provide a well behaved, repeatable measurement over a wide frequency range. These measurement systems meet or exceed the above requirements and have been in use for approximately ten years.