Sanyo 50" sound issues?

I have received a Sanyo DP50842 50" television and I am experiencing issues with the sound. When it gets turned to anything above 15, there is a weird obnoxious noise when people talk or music gets a little louder. I'm not entirely sure how to describe it, but lowering the bass and treble seemed to help a bit. If it helps, I usually watch movies/play games through an xbox hooked up to the TV, but the sounds does this weird thing when we watch normal cable as well. Anyone have any ideas what is going on or how to fix it?