There aren't 3 audio formats after export - there are only 2 (.m4a and .ogg). You only need those two to cover all browsers and platforms.
If you export to a platform where the browser engine is known in advance, Construct 2 only exports the right set of audio files, so you'll only get 1 set of audio files automatically. The settings are as follows:
Exporting to Chrome Web Store or node-webkit:
Known to use Chromium, only .ogg exported
Exporting to Windows 8 or Windows Phone 8:
Known to use IE, only .m4a exported
.wav files are never exported. They're there in case in future Construct 2 supports export-time re-encoding of your audio from the original sources.