Sounds get cut off if there are many around

Simple case: A big (maybe 100 of them?) crowd of any sound producing mob. The sound gets cut off instead of playing to the end. It's good to hear in the video. (Sorry for the bad quality and the huge overlay, the attachment limit here annoyed my so much that I turned all the settings to mininum at one point.) I've replaced the sounds step1.ogg to step5.ogg with an empty file so that it sticks out more. Whenever I open the pause screen, you can hear all the sheep sounds to end, that's how it should sound all the time.