Thanks Gator. I had seen that post prior to my install.
I have the annoying buzz especially at low volume with the amp turned up. Luckily I installed a PAC LC-1 level controller under the steering wheel so I can completely turn it off.
On a different thread by HyperS4 he wrote:
"Based on input signals, the ANC control module calculates phase, frequency, and amplitude needed for each of the four door woofers and subwoofer. The five calculated ANC woofer signals are combined in the amplifier with the woofer signals of the sound system and output to the speakers. Noises are picked up by the four microphones and sent to the ANC control unit over discrete lines."
What if I tap another signal? Are there any other low frequency signals aside from the doors and sub?