Why is Arrowhead the world’s loudest stadium? Design is only part of the answer
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In more than 100 years of NFL games, what happened at Arrowhead Stadium on Dec. 9, 1990 was an outlier.
The Broncos were pinned on their own 1-yard line and Chiefs fans were at a fever pitch. Denver quarterback John Elway had a problem when he went under center. He couldn’t hear. So Elway backed up with a pleading look for referee Gordon McCarter, who made an announcement
“Again, I have asked the defense to help lower the crowd noise. Any further crowd noise problem will result in a charged timeout against Kansas City.”
Naturally, that only made the crowd louder, and that game cemented Chiefs’ fans reputation for noise.
In addition to barbecue, Kansas City is known for the roar of the crowd at Arrowhead Stadium.
Chiefs fans set the Guinness world record when they were recorded at 142.2 decibels during a 2014 game against the Patriots.
So what makes an open-air stadium Arrowhead Stadium so loud? Is there something that aids the acoustics?
Jack Wrightson of WJHW, an acoustical consulting firm in Texas, once told California Sunday Magazine that he had consulted for the Chiefs. He had a simple answer for the decibel-raising fans.
“Building design can only contribute 5 to 10 percent to the perception of the loudness,” Wrightson told the magazine. “That’s not a trivial amount, but it’s really the noise of the crowd that makes the difference.”
Science of sound
By definition, sound is a pressure wave created by a vibration. At Arrowhead Stadium, that vibration comes from the vocal cords of fans. When more than 76,000 voices are at a fever pitch, the sound builds and begins moving in sheets, says Tom Mardikes, a University of Missouri-Kansas City professor of sound design.
“In any given section you have say 300 people, and they’re all yelling and the sound is going out generally toward the field,” Mardikes said. “The sound coming out of our bodies is directional out of the mouth but then there’s also a lot that’s coming out of the back of your head and the sides. It’s quasi omnidirectional, and so there’s a lot of sound that goes down onto the concrete floor and bounces back up.”
All the concrete and steel at Arrowhead Stadium essentially reflects the sound, although some of the noise is absorbed by all those people in the stands
The Inverse Square Law notes that each time sound energy is doubled it increases by 3 decibels. Doing some back of the envelope math, Mardikes surmised it would be possible for 76,000 Chiefs fans who are each able to general 120 decibels of sound pressure level to generate the world record sound. That takes into account the decibel loss that occurs as the sound travels away from the stands.
Smaller is louder
Another factor that could help explain why Arrowhead is louder than any other outdoor stadium in the world is its design.
A newspaper story from 1972 about Arrowhead’s opening noted the architectural firm Kivett & Meyers designed the stadium in a super ellipse and made a point of ensuring good sightlines. The firm “calculated riser heights so everyone could see that point over the person two rows in front of (them).”
That makes for better viewing of a game but it also ensures that sound waves from screaming fans have less interference.
Additionally, the closest seat was planned just 20 feet from the playing field with the upper deck is only 140 feet away.
A Penn State blog noted in 2015 that “because sound loses energy as it travels, the key is for stadiums to be as small as possible.”
Mardikes, a former Chiefs season-ticket holder, ultimately drew the same conclusion as Wrightson.
“When you’re in the stands and you get in a section where everybody starts going, it’s very loud,” Mardikes said. “And then what I’ve heard is that at some point it hits a certain thing where it sort of takes off and it hits another realm and then gets really loud.
“But I don’t think that’s the entire stadium, I think that’s in a section-by-section basis.It’s a really strange thing but I would have to say until proven wrong that I think the people in Kansas City just get really loud.”
