Active Noise Cancellation Operation

The Active Noise Cancellation system has three main components: Three microphones, the audio amplifier, and the vehicle speakers.

The three microphones are located in the headliner to monitor noise/sounds in the vehicle cabin, and are directly connected to the amplifier. The amplifier also receives a discrete engine speed (RPM) signal from the engine control module. The amplifier processes these two inputs to determine the frequency of the undesirable sound. The amplifier then calculates the appropriate cancellation frequency and outputs a cancellation signal (audio tone), which in turn sends the signal to be output by the vehicle speakers.

The amplifier performs a self-diagnostic check ensuring that the speaker and microphone circuits are appropriately enabled and then enables Active Noise Cancellation. The Active Noise Cancellation itself however does not have a self test to diagnose itself. There are no DTC's set in the amplifier. 

The active noise cancellation system is designed to moderate particular frequencies of engine noise, not to create a noise-free vehicle cabin. The system is not designed to cancel any wind or road noise. The system is intended to cancel unwanted engine sound from 1000 to 4600 RPM.

On the base 6 speaker system, the subwoofer is not used for reproducing audio. The subwoofer is used only for producing the cancellation tones for the active noise cancellation system. On the uplevel speaker system, the subwoofer is used for both reproducing audio and the active noise cancellation system tones.