I frequently use Google video chat. It was common for the person on the other end to have difficulty hearing me, which I eventually realized was because the microphone level kept being auto-adjusted to very low levels. It turns out that it was Google video chat constantly auto-adjusting the volume level and that the behavior can be turned off by editing a registry setting.
- Open regedit
- Navigate to: HKEY_CURRENT_USER\Software\Google\Google Talk Plugin
- Change the audio-flags value data to 1
The audio-flags registry key is not there on a clean install of Windows, but will show up once you change the Google video chat settings in GMail. Note that if you ever change the video chat settings in GMail then it will override the registry settings and you will need to set this flag again.