ACTIVE NOISE-CONTROL WITH THE ACTIVE MUFFLER IN AUTOMOTIVE EXHAUST SYSTEMS

This study experimentally demonstrates the use of an active muffler at tached to an automotive exhaust system to reduce exhaust noise. For im proving the signal to noise ratio in the process of estimating seconda ry path transfer functions, an on-line algorithm in which conventional inverse modeling is combined with an adaptive line enhancer is used a s the control algorithm. The active muffler is designed so that the pr imary noise and the control sound are propagated as a plane wave in th e outlet. Therefore, the error microphone could be placed outside the high temperature centers of the tail pipe, and the noise radiating to the outside could be reduced in the whole area around the outlet. The control experiment for reducing exhaust noise with an active muffler i s implemented during run-up on no load. Compared with the conventional off-line method, it can be seen from the experimental results present ed the proposed on-line method is capable of acquiring a reduction of more than 5 dB of exhaust noise in overall sound power level.