Windows 7: Sound lowers as I start up Left 4 Dead

So I am using the Windows 7 RC Build 7100 and every time I start up Left 4 Dead, change a chapter, and etc the sound of everything lowers..this happens in a few other games. I always just go to the mixer and put it back after I alt+tab but that can get annoying. So any help would be appreciated.

I am having the exact same problem. Happens with TF2 as well. What is your audio source ? I am using the Envy24 Family Audio Controller from VIA (on board my motherboard, Gigabyte G31M-S2L). According to the Gigabyte website, it uses the Realtek ALC662 codec.

Do you also use voice communication in game ? Or outside like with ventrilo ? I am wondering if that has anything to do with it.

I get the same thing in UT2004. Have a creative audigy.

Well, I figured it out. Seems Windows thinks using voice communication means everything else needs to be quiet. If you right click your speaker icon, and go to playback devices, there should be a Communications tab. It says:

Change the When Windows detects communications activity: option to Do Nothing and you should be back to normal. This worked for me!

Thanks! That did it.
Now if I could only get more than 12 FPS in Windows 7, I might actually use it.

Thanks a lot! It worked!

Try this:
ATI Radeon HD 4890 GPU announced - SlashGear

thanks, i had that problem too ... even though i dont have a (working) headset.

@bme you sir are a genius! This has been driving me crazy for 2 months. Thanks for the tip!

Registered here to say thank you.

I was having the same problem in L4D, BioShock and Crysis.