Listening to the Big Bang- in high fidelity (audio)

A 100-second recording represents the sound from about 380,000 years after the Big Bang until about 760,000 years after the Big Bang.

'The original sound waves were not temperature variations, though, but were real sound waves propagating around the universe,' he said. Cramer noted, however, that the 2003 data lacked high-frequency structure. More complete data were recently gathered by an international collaboration using the European Space Agency's Planck satellite mission, which has detectors so sensitive that they can distinguish temperature variations of a few millionths of a degree in the cosmic microwave background. That data were released in late March and led to the new recordings.

As the universe cooled and expanded, it stretched the wavelengths to create "more of a bass instrument," Cramer said. The sound gets lower as the wavelengths are stretched farther, and at first it gets louder but then gradually fades. The sound was, in fact, so "bass" that he had to boost the frequency 100 septillion times (that's a 100 followed by 24 more zeroes) just to get the recordings into a range where they can be heard by humans.

University of Washington, Listening to the Big Bang- in high fidelity (audio), 2013