The 1.13 snapshots upgraded from using LWJGL 2 to 3, which included a new version of OpenAL. There was a bug about sounds being too directional, which was resolved as intended due to the OpenAL change. However the main issue I'm getting seems to be a different one: strange filters are being applied based on the direction of your head, and the overall sound quality is noticeably worse than before.
Here is a comparison of repeatedly breaking a grass block in 1.12.2 and 17w43b:
Notice how the 17w43b version sounds less crisp than 1.12, and turning your head up and down changes the amount of high frequencies. This becomes problematic if you move around as sounds play and makes them sound distorted.
Here is also a (slightly less obvious) comparison of me randomly spawning and punching mobs:
I wanted to see if other people are getting similar issues, or if it's a problem with my audio setup. It seems I'm not the only one noticing this however.