| 摘要 |
<p>PURPOSE:To reduce the influence of sneak path of a sound due to a noise eliminating speaker. CONSTITUTION:A noise eliminating means is constituted of two non-directional characteristics microphones 5a, 5b arranged in the vicinity of a blower 2 in a duct 1 at a prescribed interval along an air flow direction in the duct 1, a signal level adjusting means for variably controlling the signal levels of output signals from the microphones 5a, 5b, delay time adjusting means 6a, 6b for variably controlling the delay times of the output signals from the microphones 5a, 5b, and a subtracting means 9 for mutually subtracting the output signals of the microphones 5a, 5b which have been adjusted with their signal levels and delay times and single directional characteristics having maximum sensitivity in the direction of the blower 2 as the whole microphones 5a, 5b is applied by adjusting the signal level and delay time of an output from either one of the microphones 5a, 5b or that of outputs from both the microphones.</p> |
