Adaptive active control on the acoustic transmission of the acoustic sources in aperture at low frequencies

In this paper, the active control on the sound transmission of both pure-tone and dual-tones sources in aperture by using an adaptive controller is discussed. In order to simplify the involved control process to make both the involved adaptive filter of system simpler and a good effectiveness of active control become practicable, the serious influence of acoustic feedback produced by the secondary source on the effectiveness of the control system is greatly reduced by using a vibration accelerometer to replace an acoustic microphone. Therefore, only either a 7th or 13th order FIR filter is needed for the adopted system to reach a good effectiveness of active control on the acoustic transmission of either a pure-tone or a dual-tones source in an aperture. The corresponding steady anenuation of acoustic pressure locally, at the position of error microphone, by 32 and 25 dB for, respectively, a pure-tone and a dual-tones source, are reached below a frequency of 630 Hz. Their corresponding anenuations of acoustic transmission power through the open end of an aperture by both 25 and 17 dB are also obtained. (C) 1998 Elsevier Science Ltd. All rights reserved.