NUMERICAL-SIMULATION OF ACTIVE CONTROL WITH ONLINE SYSTEM-IDENTIFICATION ON SOUND-TRANSMISSION THROUGH AN ELASTIC PLATE

An adaptive control algorithm with on-line system identification capab ility has been developed. One of the great advantages of this scheme i s that an additional system identification mechanism such as an additi onal uncorrelated random signal generator as the source of system iden tification [Eriksson and Allie, J. Acoust. Soc. Am. 85, 797-802 (1989) ] is not required. A time-varying plate-cavity system is used to demon strate the control performance of this algorithm. The time-varying sys tem consists of a stainless-steel plate which is simply supported on a rigid cavity where the cavity temperature can depend on time. For a g iven externally located harmonic sound excitation, the system identifi cation and the control are simultaneously executed to minimize the tra nsmitted sound in the cavity. The control performance of the algorithm is examined for two cases. Keeping the cavity temperature constant fo r the first case, the external disturbance frequency is swept with 2 H z/s from below to above a resonance frequency of the plate-cavity syst em. The simulation shows an excellent frequency tracking capability wi th cavity internal sound suppression of 40 dB. For the second case, th e cavity temperature is lowered to a half of its original value in 60 s while the external sound excitation is fixed with a frequency. Hence , the cavity resonant frequency decreases and passes the external soun d excitation frequency. The algorithm shows 40 dS transmitted noise su ppression without compromising the system identification tracking capa bility. (C) 1996 Acoustical Society of America.