The Application of Acoustic Feedback Separation on the Active Control of Sound Transmission in duct

• Main Authors: TSAI YAO CHUNG, 蔡燿仲
• Other Authors: K.T.Chen
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/60568117434882462252

碩士 === 國立臺灣大學 === 造船及海洋工程學研究所 === 89 === This study discusses the control effectiveness of adaptive active control on the acoustic transmission through a duct by separating acoustic feedback from the control system. To get the best control effectiveness, the combination of LMS algorithm with either a FIR or a IIR filter is used to be the main control system for this study. In adaptive active control experiment, a mini type accelerometer is used to be sensor to determine the transfer function of path from the reference microphone to the secondary source when two source are being in optimum actively controlled. Thereafter, subtracting the acoustic feedback field produced by the secondary source, the resulting signal is used to be the reference signal of the digital filter involved for much more attenuation of residuary acoustic field downstream. The result in this study clearly shows sound intensity attenuation downstream the duct by, respectively, 30 and 20dB for pure tonal and dual tonal sounds are reached.