| 摘要 |
<p>A noise cancellor includes a first sensor (22) for detecting a noise generated form a driving device (10) and converting the noise to electric signals. A signal processor (25) receives the electric signals and forms control signals by multiplying the electric signals by a predetermined factor series. In response to the control signals, a speaker (30) produces sound which interferes with the noise so as to cancel the noise at an object point (13). A second sensor (26) detects sound at the object point and converts them to electric signals which are inputted to the signal processor. The signal processor switches the control mode, in accordance with a predetermined condition, to an adapting active control wherein the factor series is changed in response to the electric signal applied from the second sensor or an active control wherein the factor series is fixed.</p> |
