Out of Control
Join Date: Oct 2004
Location: Orange County, CA
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the ANC system uses a mic in the cabin to "listen" for excess noise and specifically for the noise/vibration caused when VCM shuts off 3 cylinders on the hybrid. when it hears this sound, the system generates sound waves that are complete opposite of the unwanted sound to in effect cancel out the sound. this sound is played back by the head unit though the speakers.
you amp is probably amplifying the reverse waves generated by the ANC. if you disabled the system, you would still hear the deep vibration/booming sound, but coming from the engine instead. has it recently started doing this or has it been this way since the beginning (your other thread is 9 months old).
2006 BMW 330i 6MT (Alpine White/Terra)