GMA phased array for active echo control of underwater target.

Aiming at the special requirements of low-frequency echo control of underwater targets in high pressure environment, a low-frequency miniaturized active control unit with thickness less than 50 mm was designed based on Terfenol-D, a giant magnetostrictive material. Based on that, a kind of light and thin underwater large plate smart acoustic structure was constructed. It was used for low-frequency active echo control of underwater targets. The active control unit was constructed into a flat smart acoustic structure using a 4 × 4 array distributed design. The active control system based on multi-channel adaptive filter was used to test the echo control performance of the flat active acoustic structure, which can achieve significant noise reduction level in less than one second. And the sound absorption coefficient of 0.8 or more can be achieved at a high pressure of 1 MPa. When the sound wave was incident on the surface of the underwater target obliquely from −10° to +10°, the phased array method was used to make the pointing angle of the GMA array consistent with the incident angle, which could control the surface echo of the active structure very well, and the sound absorption coefficient is close to 0.9. The giant magnetostrictive smart structure combined with the active control system is a new type of low-frequency underwater noise reduction technology. [ABSTRACT FROM AUTHOR]