Underwater acoustic measurement facilities at NRL/USRD

Abstract

At the beginning of World War II, the United States recognized the need for establishing systematic methods for calibrating and evaluating sonar transducers and established the Underwater Sound Reference Laboratories. The Underwater Sound Reference Detachment of the Naval Research Laboratory evolved from this beginning and now serves as the focus for underwater acoustic metrology in the United States. It functions as a ‘‘National Bureau of Standards for Underwater Acoustics’’ by providing two types of reference services for a fee. Calibration, test, and evaluation services and standard transducer loan services cover the frequency range of 0.2 Hz to 2 MHz. This paper covers the measurement facilities for carrying out the metrology function and the measurement methods for setting the primary standards and the loan standards. Evaluation of sonar transducers and some of the ongoing research in calibration measurement methodology is also discussed. Finally, some comments are made about calibration system requirements for implementing new measurement techniques.