Read this bug.

https://bugs.maemo.org/show_bug.cgi?id=6784

EXACT STEPS LEADING TO PROBLEM:
1. Settings-Profiles-Ringing tones
2. select an mp3 audio (high quality) and click on Save
3. call yourself and listen to ringtone, the speaker is cracking

I tested on three different devices, all produced this bug!

Please, test it and prove this error is existed, thanks!