| 摘要 |
<p>An active control type noise reduction apparatus capable of exhibiting an excellent noise reduction effect over a wide frequency band. From a dummy noise source (18) arranged in the vicinity of a noise source (S), an M-series signal sound is radiated. A control point microphone (25) is arranged at a control point C in the vicinity of the upper side of an acoustical insulation wall (10) and according to the output of this microphone, a filter coefficient for reducing the M-series signal sound is calculated by a computer (26) and the obtained value is set to a filter. The filter performs digital filtering by using the digital value of the output of the sound source microphone (20) arranged in the vicinity of the dummy sound source (18) and the preset filter coefficient and radiates a control sound to reduce the noise from a control loudspeaker (14) according to the filter output.</p> |
