Even though I use all Linux tools to make my ringers, with the exception of pvconv.exe (Wine handles that), this isn't really a Linux tip, but I'll put it here anyhow.
I've noticed when I create looping ringers for my Samsung N400 phone, I get a small gap in the sound between loops. Up until now, I didn't know the length of that gap, so I had to guess and remove some audio from my master audio file to compensate. The sound files still don't sound right, especially with a heavy beat. So tonight I counted out the repetitions of a 2.5 second clip before the loop playing on my phone caught back up with the master playing on my computer. 50. So, if I'm cacluating that correctly, there's a .05 second gap between repeats of the clip pn my phone. So to compensate, I have to remove .05 seconds of audio from the clip to make it loop in beat.
Just thought I should take note of this somewhere, and maybe someone else could make use of that info as well.