ASA 126th Meeting Denver 1993 October 4-8

3aSA15. Active structural acoustic control with broadband disturbances and real time structural wave-number sensing.

Julien P. Maillard Chris R. Fuller

Vib. and Acoust. Labs., Dept. of Mech. Eng., Virginia Polytech. Inst. and State Univ., Blacksburg, VA 24061-0238

The present work gives further developments and experimental testing of a new time domain structural sensing technique for predicting wave-number information and acoustic radiation from vibrating structures. Most structure-borne active sound control approaches now tend to eliminate the use of microphones located in the far field by developing sensors directly mounted on the structure. In order to reduce the control authority and complexity required to minimize sound radiation, these sensors should be designed to provide error information that is solely related to the radiating part of the structural vibrations, i.e., the supersonic wave-number components. The approach discussed in this paper is based on estimating supersonic wave-number components coupled to acoustic radiation in prescribed directions. The spatial wave-number transform is performed in real time using a set of point structural sensors with an array of filters and associated signal processing. Experimental results on planar radiators show that only a few point sensors are required to provide accurate radiation information over a broad frequency range. The use of the sensing approach is then experimentally demonstrated in the time domain LMS active control of broadband sound radiated from a vibrating plate. [Work supported by ONR.]