[Scott Dorsey]

wrote:
Then I tried really putting a loud sound into the mic. It's my voice
droning and changing pitch quite loudly in the microphone. The
waveform is so strange and not symmetrical. It undulates with the
raising and lower of the pitch of my voice:

Link to picture of waveform:
http://www.postimage.org/image.php?v=gx1nuWE9

Does anyone know what is going on?

It's your voice. It's like that, because of the way your vocal cords
work. There's a really great paper on the subject in a book called
_Physiological Acoustics_ in the Benchmark Papers in Acoustics series.

Most commercial recordings don't look like that, because they have
been compressed and phase-rotated to make them louder.

My first reaction was DC offset, but I use Audacity's "Remove DC
offset" function and the waveform doesn't change.

Yup, because it's not DC offset, it's just asymmetry. If you think the
voice is bad, you should see the huge spiky waveform from a trumpet!
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."