Back in 2006, NASA added ARCADE (Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission) to a massive, chained balloon and let drift into space. They were plan was that ARCADE to pick up weak radio signals and primary heat traces from distant stars. Instead, researchers got to hear something they called as a "boom."
This developed to be known as the "space roar." This noise was six times stronger than any sound they were expecting. Scientists still to this day can’t determine if that intense boom was from distant stars or anything else. Learn more about this in the video below: