Good audio quality is crucial to a successful meeting (much more so than Video). Firstly, ensure you are using a high quality Combined Audio Headset and Mic (such as Logitech). Secondly, click on the AV Controls...
Choose the Audio Tab....
Click Advanced....
Turn off the Audi Transmit Gain control
Set the Gain Control so that your normal voice peaks in the yellow region, and that the indicator rarely enters the Red region.