Evaluation of sound-insulating material for use underwater

The performance of underwater sound-insulating material varies both with frequency and hydrostatic pressure, and experimental evaluations were necessary to check theoretical predictions. A novel technique was devised for this purpose involving a back-to-back, dual-piston source with known radiating characteristics. Material evaluation consisted of the application to one piston face, provision being made to monitor changes in the radiation characteristics over a frequency range 600–10 000 Hz and at hydrostatic pressures to 2.76 MN m−2. The technique, designated SARC (Submersible Acoustic Radiation Comparator), was designed to operate within a suitable pressure vessel or, alternatively, in free-field deep-water conditions. Results obtained compared favorably with predicted material responses. The advantage of SARC over the more traditional evaluation methods, such as waveguide techniques, concern the increase in the scale of evaluation, and ease of data acquisition due to a real-time evaluation capability.