If there's one thing the NFL promises each year, it's that nobody should feel comfortable at the top.

The fans of the Kansas City Chiefs proved not only that this week; they also showed something brand new: that they're officially the loudest sports fans in the world.

Less than one month after the Seattle Seahawks' "12th Man" broke the record for loudest crowd roar at a sports stadium, the 76,394 at Arrowhead Stadium rallied behind their undefeated Chiefs to raise the bar even higher.

The official final reading: 137.5 decibels. It eclipsed the Seahawks fans' mark by less than a decibel.

“It was out of control today,” Zach Aaron, Chiefs game day engineer, told the team's web site. “It was the loudest thing I have ever heard for the longest time I have ever heard."

The record-breaking peak reading came on a sack of Oakland Raiders quarterback Terrelle Pryor with 42 seconds left in the game. It was a fitting cap to a defensive masterclass from the Chiefs, who sacked Pryor 10 times overall en route to a 24-7 win.

The victory took Kansas City to a perfect 6-0 start on the season, the team's best run out of the gate in 10 years.

Long proponents of a reputation as some of the best and most supportive fans in the NFL, Chiefs followers had fallen on hard times recently, with their team recording only one winning season in the last six.

But in a season in which so much is going right for Kansas City in its turnaround on the field, the achievement by those in the crowd took a unique turn in the spotlight Sunday, even earning praise from the players after the game.

"Congratulations to our incredible fans at Arrowhead," Chiefs CEO Clark Hunt also told the team's web site. "Not only were they loud, but they knew when to be loud and helped propel their Chiefs to victory. They proved what we've known for a long time - Chiefs fans are the best and loudest in the NFL."