Evaluation of electromagnetic source for ocean climate acoustic thermometry at Lake Seneca

Abstract

A compact electromagnetic monopole source, requiring pressure equalization, was evaluated at the Naval Underwater Systems Center at Lake Seneca during July 1992 by scientists from the Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS) and from the Woods Hole Oceanographic Institution and other American organizations. The titaium source was developed at the IAP RAS. The source has a mass of 123 kg and a diameter of .54 m. The source cannot be thought of as a single unit; rather the characteristics of the transmitted signal depend on a transmission system consisting of the source, the power amplifier, and a computer. The computer and the amplifier send specially adapted signals to the source to produce the desired acoustic signals. Measurements indicate the acoustic system as a center frequence of 225 Hz, a bandwidth of about 50 Hz, an associated pulse resolution of about 0.02 s, a source level of about 198 dB re 1 μpa @ 1 m, with an efficiency of about 50%. The system has an efficiency of about 67% near 225 Hz, the resonant frequence. The source is suitable for mounting on autonomous ocean moorings for several years as part of a system of monitoring climatic temperature changes over basin scales.