In an active noise control apparatus in which an audio signal and a noise control
signal are mixed to thereby sound a loudspeaker inside a motor vehicle, a general-purpose
audio head unit cannot conventionally be freely changed for the one already mounted
on the motor vehicle. As a solution, an active noise control unit is provided with
a buffer amplifier and a mixer. An audio signal amplified by a power amplifier
in an audio head unit is adjusted in level by the buffer amplifier such that a
level of an audio signal outputted after amplification by the first amplifier becomes
substantially equal to a level of the audio signal outputted from the audio head
unit. Then, at the mixer, a noise control signal outputted from an active noise
controller is added to an audio signal outputted from the buffer amplifier. Therefore,
any audio head unit can be freely changed for the one already mounted on the vehicle
as long as the audio head unit contains therein a power amplifier.
