There are several ways to attenuate Volume of Audio in PrE. This article goes into detail on several of those: http://forums.adobe.com/message/3472343#3472343
The Audio Volume Keyframes (applied in at least one of two ways), will do exactly what you want.
Good luck, and hope that helps.
Thank you very much for such a quick answer. This forum is great! Bruce
You are most welcome.
Should you need any clarification on anything, do not hesitate to ask - that is what we are here for.
Good luck, and happy editing,