Sound distorted

This is a very bizarre problem that I can't find in any other thread.

Yesterday, my iPad's audio output was working normally, but the first time I used it today the sound was distorted and reminded me of a badly tuned radio. (In fact every now and then I hear what sounds like classical music.) At first I thought it might be a problem with my headphones, which are decrepit anyways, but the distortion is also there when I use the built-in speaker. The hissing is loudest when the audio is just silence. I hope this isn't some kind of capricious bug.

Thanks for any help! This issue makes Pimsleur's Mandarin Chinese quite difficult to follow!