The Big Bang Sound in the simulation is derived from the sound propagating as compression waves through the plasma/hydrogen medium of the early universe some 100 to 700 thousand years after the initial Big Bang… For the convenience of humans, who could not hear such low frequencies, I have increased them to the audio range of the human ear.
Big Bang sounded like a deep hum describes the sound’s origin in laymen terms:
To produce the sound, Cramer took data from NASA’s Wilkinson Microwave Anisotropy Probe. Launched in 2001, the probe has been measuring tiny differences in the temperature between different parts of the sky.
From these variations, he could calculate the frequencies of the sound waves propagating through the Universe during its first 760,000 years, when it was just 18 million light years across. At that time the sound waves were too low in frequency to be audible. To hear them, Cramer had to scale the frequencies 100,000 billion billion times.