| 摘要 |
PURPOSE:To provide the stand-alone type electronic sound elimination system which can follow up large variation in the noise level in an air duct and has high performance. CONSTITUTION:A sound wave which is opposite in phase and equal in sound pressure to a sound wave propagated in the air duct 1 from a noise source is generated and the operation of sound wave interference is utilized to positively eliminate the propagated sound wave by this electronic sound elimination system. In this system, an input level adjusting circuit 61 which adjusts the level of the input signal from a sensor microphone 2 and an output level adjusting circuit 63 which adjusts the level of the driving signal outputted by a controller 6 to a speaker 3 are added, and the level adjusting circuits 61 and 63 are automatically controlled by a level control circuit 64. Namely, the level control circuit 64 controls the input level adjusting circuit 61 according to the input signal from the sensor microphone 2 so that the input signal to the controller 6 is optimized and also controls the output level adjusting circuit 63 corresponding to the level adjustment of the input level adjusting circuit 61. Consequently, even when the noise level greatly varies, the input level to the controller 6 is optimized to obtain desired sound elimination effect. |
