sound problem in samsung galaxy s3 GT-I9300 topic

hello guys I have a sound problem with my Samsung galaxy S3 Gt-I9300. when I playing music in my device sometime it work fine and sometime suddenly drop to about 50% below even though I max out the volume or restart my device it doesn't solve my problem.

umh is it the hardware of my phone or the rom that I am using causes the this mess. please help me. : thanks.