GameDev Notes's Post

TIL (today I learnt) that MP3 is the worst format for looping sounds.

The MP3 specification does not define if there should be any delay at the start of an audio track, so when you export your sound most of the codecs just add a little bit of silence (a fraction of a second) at the start of the file and your loop will hiccup.

OGG or WAV will do the trick.
By: via GameDev Notes