Sometimes the sound levels on recordings can either be distorted, echoey or too low. You can adjust this using the flash settings on the webcam screen.
Make sure that the webcam screen is ready, and click the cog icon to access the flash settings.
Then goto the Microphone settings which is the 3rd icon along the bottom:
You can make sure you have the correct mic using the red arrow.
You can change the recording volume using the volume slider and you can click the check box to reduce echo as well.
Test the sound and watch the green level meter move up and down. Ideally you want it to periodically hit the top, but generally maintain a level around the yellow green zone.