We probably all know about the hidden diagnostics menu and the audio menu, but are there any others we can access?

 

what is the hidden audio menu?

 

It's a Honda radio thing. I believe you hold the (1) and (6) buttons down and press the knob to turn the radio on. You will see a readout in the little screen that's above the Navi screen that shows the clock and radio channels. You can cycle through some options, one of which can toggle the Active Noise Cancellation on/off (not permanently though, its turns on again when you restart the car).