Dear Rad,

please have a look at the nice video:

https://www.youtube.com/watch?v=sPScqP3mFKQ

and other links:

https://van.physics.illinois.edu/qa/listing.php?id=2679

https://www.real-world-physics-problems.com/science-experiments.html

In short: the sound is due to cracks caused by strong mechanical stresses induced by strong temperature gradients when pooring water onto sufficient deeply frozen ice.

Dear Dr. Martens

That's is what I guessed, but I wanted to hear it from an expert.

Thanks a lot and the warmest.

This seem to be the precise reason -- trapped bubbles. I rather feel it as an implosion.

In general, Dear Rad Maythil

What happens is a first-order transition from one state of matter to another one, which implies energy, that energy has to go somewhere. The explosion is part of that energy converted into sound energy (sound waves).

I rather would say that is some coalescence of drops of water that finally come together but in a very fast fashion. Probably I am wrong, but nothing else comes to my mind now.

Interesting question.