University Park, Pa. — How loud can 110,000 people be?
That's what engineers from Penn State's graduate program in acoustics set out to measure at Saturday night's Penn State-Iowa football game.
Andrew Barnard, a senior research assistant at the university's Applied Research Laboratory (ARL) and acoustics doctoral candidate, said the Department of Intercollegiate Athletics wanted a better understanding of how crowd noise works in Beaver Stadium.
Barnard and a small group of acoustics faculty and graduate students spent Friday afternoon running tests at Beaver Stadium. Using a white-noise generator and an air horn, the engineers measured the sound from different parts of the student section, going up and down the stands and moving from the senior section to freshmen section.
'We wanted to judge how effectively a sound source would reach the field, comparing say, someone screaming from this spot versus another spot," said Ryan terMeulen, a fourth-year acoustics graduate student.
The white-noise generator, which is about the size of a small suitcase, "generates constant sound energies across a wide array of frequency," terMeulen explained. The air horn, on the other hand, "has more sound energy at higher frequencies."
As terMeulen blasted sound from various parts of the student section, Barnard stood at the south end of the field to measure it. Barnard said he noticed a stronger echo from the south end zone, as opposed to the east side stands.
Also on hand was Steve Porter, an account manager with HEAD acoustics of Brighton, Mich. Porter brought along the company's HEAD Visor, a device that allows engineers pinpoint sounds in a specific location.
"It's an array of microphones splayed out in a pattern with cameras that allows you to find where the noise is loudest," he said of the flower-like HEAD Visor. "It allows you to hear what's coming out in a particular loud spot, not just all of the noise."
Porter said the machine is used to pinpoint frequency and noise level. An automotive engineer might use the HEAD Visor to find out where a specific sound is coming from in the chorus of noise from a car engine.
The HEAD Visor displayed a real-time image of part of the student section with an orange dot showing where it detected terMeulen's sound blast.
Unfortunately, Saturday's rainy weather did not permit the team to use the HEAD Visor, as the engineers could not risk damaging the unit's delicate sensors and electronics.
Disappointed but undaunted, the team arrived at the stadium hours before the game's kickoff to begin installing sound meters throughout the stadium. The team placed meters on each goal post, on each side of the 50-yard line, on top of the press box and on top of the south end of the luxury suites.
At game time, Barnard and terMeulen, along with graduate students Tara Tubbs, Scott Porter and Holly Smith; alumnus Jason Bostron; Stephen Hambric, acoustics faculty member and head of ARL's structural acoustics department; and Anthony Atchley, associate dean for research and administration and chair of the Acoustics program, stood on each side of both 10-yard lines with sound meters on poles pointed towards the crowd. For four quarters through light and heavy rain, the team remained at their posts measuring sound.
Barnard said crowd noise was the loudest when Iowa had the ball, and said the maximum noise level was 110 decibels for brief moments in the game, which is similar to the level experienced in front of a speaker at a loud rock concert.
"At this level, it is only possible for the players to communicate with each other from within about a foot using maximum vocal effort," Barnard said.
When Penn State was on offense, the noise level peaked at 75 decibels, which is closer to the level of everyday conversation and allows for communication distances of up to eight to 32 feet, depending on vocal effort.
He said the noise level was very comparable to the 2007 Ohio State-Penn State game at Beaver Stadium. Barnard and his team will return to make more sound measurements at the upcoming Ohio State-Penn State football game on Nov. 7.
"Hopefully we'll get some more good data and a win from the team," he said.