After working fine for the last 10 months or so, the mic on my N900 appears to no longer work. Callers cannot hear me on voice calls, and the voice recorder app appears to record silence. I have tried rebooting. I'm assuming that the hardware failed, but before being without my phone for weeks with a warranty repair, I'd like to 100% rule out software (like the FM Radio bug from last Dec that set the mixer improperly).

Does anyone have any recommendations for low level commands to reset the mixer or otherwise read raw from the microphone driver or some test or something so I can be positive it is a hardware issue before sending it in?