I'm having the same issue...
I do online gaming and I've had Windows 7 installed for a while. Initially I did NOT have this issue.
I use TeamSpeak 3 to communicate with the members of our gaming group and separately there is an 'in-game' communication that we use. I've had no issues until recently. I can't figure out what would have changed but now, I can't be heard "in-game".
1st thing I tried was to exit game and go into windows (Windows 7 ultimate 32bit) and try to use the Sound recorder program (Start/All Programs/Accessories/Sound Recorder) and it was NOT picking up my voice. TS 3 was working fine, but Windows 7 wasn't detecting my voice unless I Spoke really loudly and very close to my mic.
I thought it might be my headset, ordered new one...it arrived and SAME ISSUE.
I thought it might be my soundcard...Creative X-FI Fatility pro gamer I updated
drivers...SAME ISSUE
I thought it might be my soundcard...REMOVED IT and used onboard sound (Mobo is Gigabyte P55A-UD4P) SAME ISSUE
The only variable that hasn't been eliminated is Windows 7 ITSELF...and with all the posts/topics I see on this subject I'd say we're on to something. There's DEFINITELY a sound/mic issue with Windows 7.
I'm out of things to try except a new install. However, if sound issue is a result of a fairly recent Windows update then it'll probably just resurface. Perhaps I'll go back to XP using same hardware to verify that it's not a hardware issue?
Out of things to try...