If you're looking for a way to make a ringtone sound louder without distortion, then you need to use an audio editing package with a multiband compressor and a limiter.

We've discussed these tools here before in terms of how it relates to audio production and the perceived differences in volume between different CDs. But for ringtones you'd want to really go over-the-top with the settings.

A compressor essentially works like a magic gnome sitting with his hand on the volume knob. When the peaks get loud, he turns it down, when the music is softer, he turns it back up again. It has attack and decay settings that control how quickly he can twirl the knob in each direction, and a ratio setting that controls how far he twirls the knob. This lets you increase the overall volume of the track without distorting the peaks. It's sort of a "soft" adjustment which kind of changes the character of the music.

A limiter works very similar to a compressor, except it's more like a brick wall. All it does is smash down the peaks. A limiter can let you make the music sound VERY LOUD without distorting the peaks and without changing its character much. This will be the most useful tool in your arsenal when trying to make ringtones louder.

A multiband compressor will be especially useful when trying to make ringtones sound good coming out of a phone speaker. It's like a compressor combined with an EQ. You get adjustable frequency ranges to compress. You can do things like make bass frequencies sound more prevalent without making small speakers (like the one on the phone) distort.

Have a look at Reaper as a free multitrack audio editor (although you don't need multitrack for editing ringtones, it's fun to have), and the best part is that it supports VST *plugins*, and you can find all sorts of tools like compressors and limiters as VST plugins.