Subrata Paul you ask a very good question, what happens to the sound?
I think the answer is: what usually happens to sound. It travels. And its energy spreads out until it fades into background noise and becomes undetectable.
An important part of cosmology is calculating the SPEED OF SOUND in space at various times like around year 370,000 when the CMB originated because the speed of sound helps to determine the size of the acoustic waves that we see frozen in the CMB. the sound waves, called acoustic waves, are shown in density fluctuations which we detect as temperature fluctuations in the CMB.
How big the frozen sound waves look in the sky (their angular size) helps us know how far away the "surface of last scattering" was at that time in the past, and to deduce how far away it is now.
The speed of sound can be calculated if one knows the temperature of the medium. I'm not sure but I think dark matter is involved so the dark matter density may enter in. For a cloud of ordinary matter it would depend mostly on the temperature---maybe the mean free path too. Have to look this up.
Anyway it is an important thing in cosmology, and there are ways cosmologists use to calculate the speed of sound based on known conditions at various times in the past. But basically the answer to your question is "the sound travels and spreads out, and in some conditions it can trigger more star-formation"