Active Noise Cancellation (ANC) System
The active noise cancellation (ANC) circuit is built into the active noise cancellation unit (with navigation) or audio unit (without navigation). The system helps eliminate unwanted sound from entering the passenger compartment. There are two microphones mounted in the headliner, one just behind the front overhead console and the other just ahead of the overhead rear light module. The microphones listen for low frequencies entering the passenger compartment and send a signal to the ANC circuit. The ANC system then creates a sound wave that is sent out through the speakers to eliminate the unwanted sound.
The ANC system works to cancel engine booming sound up to about 2, 000 rpm. The active noise cancellation unit receives the engine speed pulse (NEP) from the PCM and outputs a sine-wave-sound through the audio speakers to cancel low-frequency noise from the engine. The ANC system also uses two microphones to detect and monitor low frequency noise in the passenger compartment. The microphones feed information back to the audio unit which adjusts the speaker output to reduce the noise. The ANC also receives input from the door open/close (INTR LT) signal from the MICU. Anytime a door is opened, the ANC system temporarily stops working.