What are the spooky noises on Minecraft?

Usually I can tell when a sound is from a nearby mob, such as a squishy-like sound from endermen, slimy sounds from slimes, fizzing from creepers, groaning from zombies, etc. But sometimes there are those Really loud sound that don't seem to come from anywhere. Like lately there's been this intense drumming sounds. Once It kept repeating for over 30 sec, another time is just did it twice. Idk what it is and I couldn't find a page about it on the Minecraft wiki. Does the sound have a source or is it just random?

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