Software : Sonic Visualiser 4.4 
License : Freeware / Open Source
Author site :

You want to inspect and analyze what is inside the audio file ? Then, Sonic Visualiser is for you. It is a free, open-source app for Windows, Linux & Mac. It's designed for musicologists, archivists, signal-processing researchers, and anyone else looking for a friendly way to look at what lies inside the audio file.

(Link sends you to official site)

(img src : sonic visualiser site)