NFL Films has been collecting multichannel surround audio recordings from every NFL stadium for the past four years, and those sounds will be used Sunday.
Over the past few months, NFL Films' sound mixers spent hundreds of hours harvesting and cataloging sounds from each of the NFL's stadiums that they had been saving in recent years for the league's broadcast partners.
Each broadcast will have the option to create a unique sound palette for each team in that game. The sounds will be fed to the broadcast by an NFL-hired operator who is following the game and using a button panel to control playback from custom-configured software.
The different audio tracks ensure the sound that fans hear on TV will be authentic home-team crowd noise.
The Chiefs allowed a crowd of 22% of stadium capacity, or about 16,000 fans, to attend. The fans were scattered throughout the three decks.
The NFL announced earlier this month that it was finalizing a policy for artificial crowd noise. Commissioner Roger Goodell said at the time that the league would not implement a blanket policy to close all stadiums to fans, and that as long as teams follow local and state health guidelines, "we want to invite our fans in."
Goodell also said some teams could open up their stadiums later this fall.