How to play MP3 at maximum volume?

[HARDWARRIOR]

Hi!
I'm using AVAudioPlayer to play MP3 in my app. Volume property is set to 1 (according to docs it is maximum level).
But on real device sound is very quiet. Comparing to the same MP3 playing with ipod.app at ipod's max volume.
I tried to raise AVAudioPlayer.volume to 4, but got very distred sound. Same happens if I raise wave level in audio editor - heavy distorsion.
Device's volume (that is controlled by side buttons) is at max.
How can I riase volume without quality loss?
Also is it possible to stop or pause ipod.app from my app if it's playing?

PS this app is for AppStore