Tested in Chrome an Firefox on Linux and sound is OK. Maybe is problem in your browser. Cool game bro.
Im using Opera GX. I dont know if it has a reputation of doing stuff like that.
I had an issue with the MP3 not being played for my game. I changed it to Ogg Vorbis and that seemed to fix it. I'm using the latest update of Opera, and coupled with your issue, I wondering if there is a bug with the browser...
