The concept of "sound" as we typically understand it does not apply to the immediate aftermath of the Big Bang. The Big Bang was the event that marked the beginning of the universe, and it occurred approximately 13.8 billion years ago. At that time, the universe was in an extremely hot and dense state, and the laws of physics as we know them did not yet exist.
In the early stages of the universe, the conditions were so extreme that matter and energy were intermingled in a state known as a plasma. The universe was expanding rapidly, and it was filled with a tremendous amount of energy and radiation. However, it is important to note that sound waves, as we understand them, require a medium to propagate, such as air or water. In the early universe, there was no matter in the form of gas or liquid that could serve as a medium for sound waves to travel through.
However, during the early stages of the universe, there were fluctuations in density and temperature that eventually led to the formation of structures like galaxies and clusters of galaxies. These fluctuations can be described mathematically as primordial density fluctuations. While these fluctuations are not sound waves, they did give rise to the formation of cosmic microwave background radiation, which can be thought of as a kind of "echo" from the early universe.
The cosmic microwave background radiation is a faint, uniform radiation that permeates the entire universe and is thought to be a remnant from about 380,000 years after the Big Bang. This radiation provides valuable information about the early universe and helps us understand its evolution. However, it is not sound in the traditional sense that we can perceive with our ears.
So, while there were no actual sounds as we know them immediately after the Big Bang, there were physical processes and phenomena that occurred during that time that have left an imprint on the universe and can be studied through scientific observations.