Can someone explain me the origin of the sound from this YouTube video (link given)? I think this question is not completely out of topic so I am showing the courage to ask the community for help as I don't formally understand the reason.
Today I was going through this YouTube video named Ice Dropped Down Borehole in Antartica Creates Unusual Sound, from channel Storyful Rights Management, but I can't understand the reason behind the origin of this type of sound. Is it just a unusual thing as mentioned or there is something specific physicis or Physical intuition behind it( obviously there is physicis)? Then what is it?
 A: Mark Bocko from Rochester University has done a proper analysis of this effect. Here's a summary:
The two interesting features of the sound at the end of the drop of the ice into the about 80m deep bore hole are the high-pitched sound (like a stereotypical sci-fi laser sound effect or a bullet ricocheting off metal) followed by low heartbeat-like pulses.
The "heartbeats" are essentially just echoes of the initial impact sound, and the spacing between them is the time it takes for the sound to travel down the hole, reflect at the bottom, and travel up again.
The high-pitched sound is due to the hole acting as an acoustic waveguide - think of it as a big organ pipe. It "conducts" frequencies along certain "modes", and the speed of sound of the excitations of these modes is dependent on the frequency in the higher modes - the higher the frequency, the closer the sound travels to the frequency-independent speed of sound of the ground mode.
So at the top of the hole, what we hear is first the ground mode + the higher frequencies from the higher modes, followed by the slower, lower frequencies in the higher modes, creating this high-pitched sound that gets progressively lower. The deeper the hole, the longer this "pitch-drop effect" will be drawn out in time.
For more details and some helpful pictures, you'll have to read Bocko's article yourself.
