| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an active noise controller that can reduce noise in a duct without making the size of the duct large. SOLUTION: A 1st rectifier network 3, rectifier gratings 2, and a 2nd rectifier network 4 are placed at an upper-stream of the duct 1 as rectifier means in this order. A noise detection microphone 5 detects noise in the duct. An error detection microphone 6 is placed at a downstream of the noise to detect an error noise. An arithmetic means 8 receives a noise signal from the noise detection microphone 5, calculates a transfer function to minimize the output signal of the error detection microphone and outputs a control signal to a control sound source 7. The control sound source 7 radiates a control sound that has nearly the same sound pressure as that of the in-duct noise but in the phase opposite to that of the noise. Thus, the rectifier means can enhance the coherence between the noise at the upper-stream part and the noise at the downstream part to enhance the silencing effect.</p> |
