remind you 1st, this is not n series phone. so don't espect much from the media playback quality. i don't have any problem with the volume. it's sufficient for me. maybe the mp3 song that you used isn't suitable to be a ringtone. that's why you can hear is sometimes. try something like daft punk's song. i bet you can hear it. hahahaha...

about the crackling sound i think you increase the volume beyond the speaker capability. that's why crackling gsound. perhaps you can lower down the volume for the ring tone.