Miscellaneous: Bug of SOUND around the fights

[rakam180]

So, I hope I didn't post this in the wrong section (I admit I'm a bit lost, I don't post often). But my problem is, during battles, the music starts playing - 'no problem at that level' - but in the background, on top of the battle music, there's a continuous sound, like an 'echo,' as if a sound or as if you're continuously pressing a key on a piano (if you understand what I'm trying to describe). So, is this normal, or is there a way to solve this issue? Thanks in advance.