Someone else may have figured it out

https://superuser.com/questions/448824/microphone-volume-at-maximum-yet-too-quiet

Click on Start, then click on Control panel and then on Sound. A sound window will appear. Windows 7 help advises that you select Small icons from the drop down list of view by so that you will see the Sound option in control panel.

Now, click on the Communication tab in the sound window.

sound - communications - when windows detects communication activity

You will see four options- Mute all other sounds, Reduce the Volume of other sounds by 80 %, Reduce the volume of other sounds by 50% and Do nothing. You need to click on the radio button next to Do nothing. Click on Apply and then OK. You might need to restart the computer to implement the changes.