Patent ID: 8125568

Claim:
A muting device to be included in electric and electronic equipment that provides an audio output, comprising: an external sound input unit that receives a sound from without and makes an external sound; an internal sound input unit that only receives a sound from within and makes an internal sound; an internal sound mask unit that compares the external sound with the internal sound, and that, if the external sound has a component corresponding to the internal sound, removes the internal sound component from the external sound and transmits the resultant external sound; a band-pass filter circuit that samples only a sound of specific frequencies from the resultant sound and transmits the sampled sound; an input level comparison unit that receives the sampled sound, that decides whether the sampled sound signal level is equal to or larger than a predetermined reference, and that, if the signal level is equal to or larger than the reference, transmits an on-state signal; and an audio control unit that receives the on-state signal from the input level comparison unit and mutes the internal sound.