| 摘要 |
PURPOSE:To kill a discomfortable sound in view of audition for a driver in a cab, by making a state that the discomfortable sound subsists in a cab noises detectable automatically as well as making these cab noises so as to be modified by emitting another sound out of a speaker. CONSTITUTION:When a discomfortable component subsists in a cab noises to be collected by a microphone 1, a level of a detecting signal D out of a mean level detecting circuit 3 comes to less than a level of reference voltage Vr by dint of an audio signal C' out of a zone passing filter 2, while a level of a signal component obtainable out of a frequency separation circuit 4 comes to more than a level of reference voltage Vs. And, output signals out of each of level comparator circuits 5 and 8a-8c all come to 1, and also an output signal Pa out of an AND circuit 7 comes to 1. Likewise, when an engine is in the specified speed, a discrimination signal Pb comes to 1 whereby an output signal Pc is fed out of an AND circuit 10. With this constitution, such an audio signal Pd of frequency as modifying the discomfortable component is secured from an audio signal generator circuit 13, thereby driving a speaker 15. |
