| 摘要 |
<P>PROBLEM TO BE SOLVED: To adjust acoustic impedance in a frequency band that is required to be silenced. <P>SOLUTION: In a duct with sound impedance adjusting mechanism installed in an exhaust duct DC connected to a noise sound source NS at one end, and an electronic silencing system applying this duct, the duct is bent in a middle part, a projecting portion D3 is provided on a bent part AG, and a mechanism capable of adjusting the length of the projecting portion D3 is provided. In a direction from an upstream side to a down stream side of exhaust flow in the exhaust duct DC, a noise detecting microphone OM is installed in a position downstream to the bent part AG, and a secondary sound source SS is installed in a position downstream to the noise detecting microphone OM in the exhaust duct DC, and an error detecting microphone EM is installed downstream in a position to the secondary sound source SS in the exhaust duct DC. Sound waves received by the noise detecting microphone OM and the error detecting microphone EM are processed by an adaptive digital filter computing device F1, and generated from the secondary sound sours SS as sound waves for silencing. <P>COPYRIGHT: (C)2004,JPO |
