How do I mute the audio in my original video?

Thanks for the quick replies! I will try your suggestions. 

Each video track has a mute option in the header block to the left, you can mute or solo anything.

Sometimes it's faster simply to solo the one track you want to hear.

Neil

Alt/click the audio clip to select it without the video, right click and de-select enable.

Try the Mute button in the header.