Danger Warnings on NFL-Stadium Noise May Be Overstated

Last Sunday's New York Times once again put the decibel level of NFL stadium crowds in the spotlight in an article that warned of the danger to fans' hearing. As if on cue, that evening's NBC's Sunday Night Football focused in on New Orleans Saints head coach Sean Payton egging on a late-fourth-quarter rally with GET LOUD, SAINTS FANS! displayed over his shoulder on the stadium's ribbon board. The Saints won, 23-20. It also comes a month after the Kansas City Chiefs asserted the NFL record for stadium volume, at 137.5 decibels.

Both John Storyk, principal at Walter-Storyk Design Group, which has designed the acoustics and sound systems for several World Cup and Olympics venues in Brazil, and Kerrie G. Standlee, principal engineer at Daly-Standlee & Associates (DSA), an acoustical-analysis and -design company, point to flaws in the Times article and other similar assertions of high-volume supremacy, based on how they're measured.

The numbers are big but not accurate, observes Storyk, who designed the acoustics for the Mineir o Stadium and the Independencia arena, both in Belo Horizonte, and the Maracan Stadium in Rio de Janeiro. There is no disclosure as to where the measurements were taken in the stadium and how the measurements were weighted - dB/SPL, dB/C, dB(leq), etc., he observes in an e-mail. Storyk further comments that he compares a dB reading he takes on a professionally calibrated Studio Six dB meter on his iPhone with the level shown on the video display at Yankees Stadium during games there: Usually no correlation at all.

Standlee of DSA, which provided measurements of the ambient noise levels at the Woodland Sprint Boat Race Track, a USSBA race course that hosts extreme fuel-injected-engine race boats that roar at 1,000 hp at 6,500 rpm, also noted the lack of reference position for the noise measurements.

When addressing the sound-pressure level in a stadium and, ultimately, its effect on the hearing of someone in the bleachers of the stadium, you need to know the distance from the source of the sound to the measurement location as well as the level of the sound at the measurement location. he explains. If the sound level being reported was not measured at the ears of the fans in the stadium, saying the sound level in a stadium is 137.5 dB without telling you where the sound level was measured tells you only half the story. Was it in the center of the field, was it at the player's bench on the home-team side, was it at the player's bench on the visiting-team side, was it in the middle of the home-team fan side of the bleachers, and so forth.

Amped-Up Fans

John Horrell, principal at Durrell Sports, a Nashville-based sports-audio consultancy and designer of the new sound system installed at the Kansas City Chiefs' Arrowhead Stadium earlier this year, says the noise levels stadiums are achieving now are purely a result of amped-up fans, not sound systems.

Fan excitement and fan noise can be encouraged by the sound system, he says, but it's the fans that produce the high level of sound that makes for the home-team advantage in all the stadiums.

In fact, says Horrell, the new sound system at Arrowhead Stadium was installed because of the inability of the previous PA system, which was only three years old, to get above the crowd noise at its peak. That's something any sound system needs to do in order to ensure audibility and intelligibility in the event of an emergency. The new JBL VLA system powered by Crown amplifiers is, he says, the single loudest point-source system in the NFL.

Using crowd noise to throw off visiting teams' signal calling, which is what Payton and the Saints' management were encouraging on Sunday, is a time-honored tradition. In July 2012, the NFL liberalized the restraints it had once imposed on crowd noise. Since then, stadiums are free to fire up crowds with video displays when the opposing offense faces a crucial third down.

On the other hand, the league has rules in place about when and how loud audio content can be played through PA systems in NFL stadiums. However, that hasn't tamped down what has become a volume arms race for the title of loudest venue this football season. The Seattle Seahawks set their own record in September, with a decibel level of 131.9 in the first half of a game against the 49ers and, in the third quarter, raised it to 136.6.

Absent a more precise measurement, Standlee does some back-of-the-envelope math. I would expect the crowd-noise level in the middle of Century Link Field, the Sea Hawks stadium, would more likely be in the range of 100 dBA if the stadium roof was open and all 67,000 fans [in the stadium] were shouting at a level of around 90 dBA, about the highest level that can be sustained by a male voice for a period of time, at a distance of 3 ft., given the fact that the fans are, on average, seated about 250 ft. from the center of the field, he explains. Therefore, I expect the 137-dBA sound level mentioned in the article was not the sound level at the center of the field.

Team players on the field could find it hard to hear the quarterback if the crowd noise is around 10 dB over the voice level of the quarterback, he continues. That means a player like the wide receiver may find it hard to hear the quarterback if the crowd noise at his ears is in the range of 80 dBA while players closer to the center position might find it hard to hear the quarterback if the crowd-noise level was in the range of 100 dBA at their ears. The quarterback can only generate a voice level in the range of 90 dBA measured at a distance of 3 ft.

Not all acousticians were skeptical of the value of raising awareness about noise levels in stadiums. Russ Berger, who has done acoustical and other audio-systems designs for NFL Films, found the article to b

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