ELECTRORHEOLOGICAL FLUIDS AS AN ELECTRICALLY CONTROLLABLE MEDIUM AND POSSIBLE APPLICATIONS TO UNDERWATER SOUND ABSORBERS

摘要

Electrorheological uids (ERF) show a large variation of their viscoelastic properties in a strong electric field. A new area of ERF applications could be underwater acoustics where the construction of absorbers with electrically adjustable properties appears possible. For measuring the acoustic properties of ERF and the performance of hydroacoustic sound absorbers an improved impedance tube has been developed. The so-called two-microphone method provides advantages as compared to the methods used so far for impedance measurements in hydroacoustics. Using the new impedance tube, sound velocity and attenuation of an ERF have been measured as functions of frequency, field strength, and temperature. Further, a laboratory model of an absorber for underwater sound, based on the principle of particle velocity transformation with ERF as viscous fluid, has been built and tested in the impedance tube.