You may have a crashed Window of Minecraft where Java crashed so its not see able, and it was open to one of your worlds. That is where both sounds come from. Or possibly a bug.
This could be a Monitor issue, or many other possibilities. However, this is not a game issue. Test other games and alternate in between Fullscreen and Windowed.
Jerry Grace
You may have a crashed Window of Minecraft where Java crashed so its not see able, and it was open to one of your worlds. That is where both sounds come from. Or possibly a bug.