People can very rarely hear me well over the telephone. I don't know why. I sometimes use my computer because my cell phone has a terrible mic, but people still have a hard time hearing me sometimes... it also didn't help that Google Talk would constantly adjust the microphone input volume either.
I'm using Kubuntu 12.04, and the microphone input volume would constantly lower itself as I talked on GMail through the Google Talk Plugin. It would just raise and lower the volume slider as it saw fit. So frustrating.
After much Googling, I found a solution (Linux only, there's a similar registry fix in Windows though). Should work for Ubuntu, or any other Linux distro really, since it's a problem (er, "feature") of the Google Talk Plugin.
Edit the file (create it if it doesn't exist):
If it's already there, there will be a line that starts with "audio-flags="
Change it (or add it if it doesn't exist) to:
Save, Reboot, and Test