Sample Manager is an application for Mac that, as you’ll see in the below article, can be a very useful and even “indispensable” part of your audio tool collection. The article, written by Matthew McGlynn, speaks of several reasons why the app is awesome. One of them is the batch normalizing feature. I agree about that being a handy tool. If you happen to have Adobe Audition on your machine, you will have that (batch normalizing) capability as well, and you can use it on a PC.
Anyway, see Matthew’s article here http://recordinghacks.com/2012/10/03/i-love-samplemanager/