sound in terra nova's portrait

So far i have not added any outside sound. However I have leaned to take out sound I don't like by lowering the decibles in final cut express with the pen tool. When you lower this sound it leaves what I can only describe as a "void sound" which is very evident when watching the film. So what i did was take extra sound I had (sound with no one talking but just the waterfall and birds and other sounds) and put it in place of the "sound void" . if listened to closely you can here something like a churning or pumping. All in all is was improved greatly.

Now I have lots of film of terra talking about her experience and I am thinking what sound would go well with it? Maybe i can ask her about music she has been listening to latley?