When music plays in certain screens (the capsule/shuttle screen for instance), the game will sometimes make a loud buzz at the end of the bit of music that plays there, before replaying the music (and buzzing again afterward). It doesn't do this consistently, but when a screen starts the behavior it will keep making that obnoxious sound until you close the window.

This was a known issue in the old CVS code too; I had hoped that it hadn't carried over to here, but no luck there.