Cropping audio files?

I was wondering if there was a tool similar to jCrop, with the exception that instead of an image I'd allow the user to crop an audio file? Google didn't give me any useful results sadly :(

The reason why I'm asking is that I'm making a tool to convert audio files to popular ringtone formats, and only开发者_运维百科 letting the user specify the offsets in numbers is somewhat inconvenient. Obviously the tool doesn't have to be in javascript - anything that fits into a website is ok.

Here's a browser-based audio editor written in Flash that you could probably adapt (it supports cropping):

http://www.hisschemoller.com/2010/audio-editor-1-0/

One thing I found a bit confusing is that you have to hold down the play button on the editor to play the full sound.