macbook pro sound is distorted

Hi,

The distorted sound is a very common issue on MacBook Pro Retina's, you will have to replace one or both speakers (Apple sell the speakers by set). In the 13-inch Retina is a fairly easy job, but in the 15-inch you need to take out the Main Logic Board because they are undernith.

I certainly recommend taking you MacBook directly to Apple or to an AASP to perform the job. Speakers are not an expensive part.