Increasing Audio Volume/output/amplifying without distortion

Hello, newbie in need of help here.

Is there a way to increase how loud a sound file is without causing it to distort? I have used both the normalize and amplify features, however, after a certain level, the file begins to distort.

In Audacity 1.3 there is an effect called “leveller”. This is a crude type of dynamic compression effect. (See “loudness war” in Wikipedia). A much more refined version is "Chris’s dynamic compressor (easy to find with Google). You can also use a limiter (there’s a plug-in for Audacity called “fast lookahead limiter”).

[EDIT] See here: http://audacityteam.org/forum/viewtopic.php?f=28&t=9253

Awesome thank you so much. I will give it a try.