So, I've searched the literal entire internet and found NOTHING. I've even asked Mojang, but they couldn't help either.
My computer crashed the other day, and I found nothing wrong with this because sometimes I run too many things at once and it crashes. but this time, Minecraft decided not to load, so I just restarted it again. after all that, it worked but something wasn't right. certain sound effects, such as hits and placing stone and wood variants, sounded a bit off as if muffled, distorted, or just something different. and no it is NOT muted. later versions of Minecraft don't have anything wrong with the sound. (note: this is version 1.8.9) I've tried reinstalling Minecraft, opening clients without the assets folder installed, and trying to make a sound pack with everything that was missing (or all that I could find). the problem seems to come, not from resource packs, not from the assets folder, but the game itself. either the game is reading the sound files wrong, or the game is corrupted.