Well, this is plain weird. I can no longer get listenable audio using QuickVoice, although the QuickVoice mic bargraph shows about the same response to my voice; but when I try to play back a further test recording, there is virtually no audio. Playing back the test recording made after vacuuming the mic hole the day before still sounds fine. Rebooting my iPad had no effect. Yes, the volume is turned up.
So, today, Monday, my iPad2 warranty replacement arrived. Wow, talk about fast. The only surprise was that it did not have my name engraved on the back, as promised. Oh well.
After initializing my replacement iPad2 and then transferring all my backed up files using iTunes (which went fine), I nervously tried QuickVoice: The mic bargraph shows plenty of activity, and my test audio plays back loud and clear. So, there appears to have been more than one problem with my first iPad2.
I haven't had a chance yet to try FaceTime, and see if I now have two-way audio, but since QuickVoice gives loud and clear audio for a normal speaking voice in the direction of my iPad2, I expect that I will have full connectivity. Since I was a FaceTime newbie, I kept thinking that it was operator error on my part why others could not hear me; but no, it was a hardware problem, probably one that had been there from the start, but hidden since I hadn't tried using the microphone until now. Glad I discovered this before the one-year warranty ran out. And I have now purchased the additional one-year warranty. Still love my iPad2, though. Glad that Apple offers the option of first shipping a replacement iPad2, then sending your old iPad2 back. That's convenient for me, since the nearest Apple store is 25 miles from where I live. This also let me do the file transfers at my convenience, and delete all my files from my original iPad before shipping it back to Apple.