Crowd Noise

This weekend I had the pleasure of attending a professional football game. Throughout the game, when the home team was on defense, a number would pop up on the big screen showing how loud the crowd was. It frequently topped 105 decibels and the highest I saw (admittedly I wasn’t watching it intently the whole time) was 107.3 dB. So that got me thinking: I know the people around me that are yelling are giving it all they got. But I am sitting here silent. How loud is each person yelling? How much difference would it make if I yelled too? So, here we go.

First things first. How loud do these things get? In the interest of everyone’s time, and my sanity, lets ignore most sports. Baseball is too spread out. Basketball is too small of a crowd. Hockey is similar in size to basketball. Tennis…. well its tennis. So, we are down to really the two big populous sports, football and well football. That is, for we Americans, football and soccer. First, lets look at soccer.

There are some absolutely monster soccer stadiums. Wembley stadium in London sits 90,000. Camp Nou, where Barcelona plays sits just under 100,000. The record for stadium size goes to Rungrado May Day Stadium in Pyongyang at 114,000, but god knows we aren’t getting any reliable data from there so it will be excluded. Camp Nuo has been reported to register as a small earthquake because of the noise from their stadium. However, when it comes to loudest there is many who are superior. In fact, the home of FC Barcelona does not even record in the top 10. This trend will be consistent throughout this post. Apparently, size doesn’t matter.

One of the biggest factors in this argument is the geometry of the stadium. Below are pictures from Google Maps of Camp Nuo (left), the largest soccer stadium, and Turk Telecom Arena (right), the loudest soccer stadium. There is such an obvious difference it feels silly to point it out. A ROOF!

Camp nuo      Turk Telecom

 

 

 

 

 

 

Yes. Enclosing sound makes it loud. Call the ancient Greeks and tell them they got another one right. Turk Telecom Arena set the record for the loudest stadium in 2013 at an ear bursting 137.5 dB with just 52,652. That is louder than a military jet taking off from an aircraft carrier.

Now the question is, how does that match up against football stadiums here in America? The largest stadium in America is the Michigan Wolverines stadium which sits a whopping 109,901 attendants. That’s a number you would expect to see as a population, not an attendance.  So how loud do they get in the “Big House”? An impressive, yet not astronomical 110 dB. The loudest college football game was the University of Washington in 1992 in their game against Nebraska.  Their stadium of 70,083 people got to a rocking 133.6 decibels. Again fellas, size doesn’t matter

Impressive numbers for a college stadium. But when it comes to breaking records, leave it to the pros. The Kansas City Chiefs, with their Arrowhead Stadium of 76,416 people, own the record at a head splitting 142.2 decibels. 140 dB is typically used as the point where noise breaks the “pain threshold”. It is the equivalent to standing next to a tornado siren that is going off. Possibly more impressive, they broke this record in the last few seconds of the first quarter of the game. When they set the 142.2 dB record in 2014 it was the second time they had been in the Guiness Book of World Records for loudest stadium. In 1990 the referees warned the whole stadium that if the crowd noise became a problem again the Chiefs would be penalized. This warning came after a complaint about how loud it was by the opposing quarterback, John Elway.

So, we agree that shape of the stadium is a big factor in the noise of the crowd. We would assume the loudest stadium must be enclosed, right? Wrong!arrowhead

Arrowhead stadium is dramatically topless. How then do they have such a loud crowd? To physics my friends. The University of Indiana’s Physics department released a paper on just this topic that should shed some light on it. We won’t get caught up too much in the math just yet. The general concept of crowd noise is that it is logarithmic. The way it works out is that if the number of sources is doubled, the increase in sound goes up by 3 dB. The normal intensity of talking is about 60 dB. So, if 2 people are talking simultaneously, it goes up to 63 dB. 4 people, 66dB and so on. Now, let’s extrapolate that out. Below are two graphs so you can get a feel for just how this works with large numbers. Adding one person to a single person crowd, adds 3dB. But to get that same 3dB increase from a crowd of 20,000, you have to add 20,000. This is the general shape of logarithmic relationships.0-100.PNG

0-120k.PNG

Now we get a better feel for why Michigan’s 110,000 people don’t necessarily heavily outweigh the KC Chiefs 76,000. To get just another 3 decibels from population alone, you have to double it. That leaves us to the shape of the stadium, and the wild card, the intensity of the crowd. There is no simple way to show the acoustics of the Kansas City stadium, but there is no roof, just an overhang on one side. In the interest of simplicity, we will ignore that. We will take an introductory physics perspective and frame the remainder as: If these two crowds were in the same shape stadium, what does that mean for their intensity?

Using the equations from the University of Indiana’s paper, we can back calculate the rough average of intensity from each attendant. The University of Michigan, with 109,901 attendants reached a nice 110 dB. As seen in the graph above, that is essentially the same as everyone talking at once. In that Washington vs Nebraska game, the average is about 85 dB. Which puts each attendant yelling but not quite as loud as they can. Traditionally, the human voice yelling peaks around 90 dB.  So where did our record setting Chiefs fans get to? 93 decibels on average for their 76,416 attendants. Louder than a yell is traditionally held to be.

So, what do we really prove here. First things first, this is not to say that the KC fans were reaching 93 dB. Again, this is ignoring acoustics and geometry of the stadium. But there are domes all throughout the sports world, and they do not dominate the noise records. This leaves us with one undeniable truth. Some fans are just more intense. When it comes to sports crowds, quality beats quantity.  I found myself wondering how much impact I would make if I added my voice to the onslaught of fans. I was curious how additive sound sources work, And Now You Know.