Sorry if this is old news:

Diagnosis mode (try at your own risk) for all Honda/Acura radios?:

Turn ignition on

Radio should be off

Hold down "1" and "6" at same time and then hit "Power" button

"DIAG" appears in upper display.

Pushing the 1-6 buttons will give you info about radio. I found out you can turn ANC "off" by hitting ANC ON button. You will hear a really loud bass tone when you turn it off.

 

Have you driven around some with the ANC off? Can you tell much of a difference?

 

Just use your finger to cover up the microphone (hole) behind the rear sunshade button and you will hear the ANC working out of phase and the noise go up. How much of that is the ANC reinforcing ambient noise rather than cancelling out I think depends on the road surface. I have had a lot of different results with the microphone covered up, but all louder. I am too lazy to turn off the ANC, I suppose I might try it in the next couple of weeks.

 

I drove into work this morning with the ANC off and couldn't tell a whole lot of difference. It's interesting that when it's on and you cover up the mic you get the loud rumbling bass sound (leading you to believe that it's really canceling out a lot of noise), but you don't get that bass sound at all with the ANC shut off. I verified that it was off by holding my finger over the mic and getting no sound differences at all. I didn't notice higher levels of outside noise inside the car either, so whatever ANC is doing is probably very subtle.

I've always wondered if the ANC actually contributes to more noticeable higher frequency engine/drivetrain sounds since it supposedly cancels out lower frequency engine and road noise which would otherwise mask the higher frequency sounds a bit.

 

It is my understanding that there are two mics for ANC--one in front and one in back.

 

That is correct. There is another microphone in the back seat roof area.

 

Do the ANC speakers cause a soft, low-frequency booming sound? I thought when I heard this initially that it was my my new exhaust, but there is no popping from either exhaust or engine when someone presses or releases the accelerator, so I know that it is not an engine or exhaust problem. The booming is a bit louder when I cover the front ANC mike.

I may try to shut off the ANC using this method to test further.

 

It doesn't appear that the ANC system can be shut off permanently. It turns itself back on when you restart the car.

The Acura website states that when the ANC system detects low frequency noise in the cabin, "the control unit passes an equivalent waveform to the Bose amplifier unit where it is amplified to an inaudible volume that matches the original sound." I shut it off again for the ride home tonight and didn't notice much difference with the ANC on vs. off. When the system is off I don't hear the low rumbling sound that I hear when I cover the mic with it on.

 

I played with turning off the ANC this morning. (unfortunately I did it by idling the car in my garage, only for my wife to walk out and assume I was trying to kill myself...oh well)

Anyway, the best way to appreciate it is to idle it and turn it on and off. You can definitely hear the difference in the exhaust note from the rear. It all but mutes that. Actually sounds more sporty with it off. I didn't really appreciate much 'tire or wind' noise reduction while driving.