Sound cuts off eventually

When I leave my computer on for too long, the sound cuts off and there is no sound. This does not happen when I am at my computer, I have to be away for it to happen. The sound only cuts off on Minecraft, not anything else. Youtube works fine, but Minecraft sound doesn't work.
How to replicate:
1. open Minecraft
2. make sure sound is turned on
3. Leave your computer on but don't touch it for about 10-20 minutes
4. Test sound, notice how it doesn't work
This is really annoying because I have to restart Minecraft every time this happens.