Delivering Sound in Large Spectator Sports Venues

When Ken Voss has Chicago Blackhawks tickets, he makes sure to arrive in his United Center seat 20 minutes before the puck is dropped. There are spectacular scoreboard visuals and on-ice projections, but the pregame hat trick isn't complete until Jim Cornelison belts out "The Star Spangled Banner" and "O Canada" into a live microphone. As Voss puts it, "To listen to the Irish baritone do the national anthem in that stadium just brings goose bumps."

Such is the power of stadium and arena sound, and Voss is not the easiest patron to impress. By day, he's manager of installed sound for high-performance audio manufacturer RCF. "Today's major sports arenas are entertainment venues," he says. "We're starting to realize that the sound system is a powerful part of the whole fan experience, even in pulling people away from their home viewing options."

Consumers accustomed to surround-sound quality in their home theaters or the personal satisfaction of cranking their car stereo bring expectations to the live sports experience that they didn't decades ago. Back then, a PA system delivered in-game announcements and little else. Now sports venue sound is designed to be as good or better than what fans are familiar with in everyday life.

"So many of the younger folks are used to wearing ear buds, and that's delivering something very different than what we can with a dynamic-range sound system," says Skip Welch, eastern regional manager for Danley Sound Labs. "A high-quality sound system can deliver a big, dynamic range and really deep lows. Ear buds don't necessarily do that."

What, then, goes into creating an earful experience for not just one individual, but perhaps a stadium of 100,000 simultaneously? Here are a few factors.
 

Individual boxes within line arrays can be angled to target specific rows of seating. [Photo courtesy of RCF]

Delivery models
There are two basic ways in which sound is delivered to the masses. In a point-source system, speakers are concentrated in one location — likely flanking an end zone video display or sitting atop a center-hung scoreboard — and they throw sound over considerable distance to the crowd at large. A distributed system, meanwhile, uses multiple speakers scattered throughout a facility to focus sound on specific sections of fans.

But even when speakers are clustered, they can target finite zones, according to Voss. "Let's say I'm putting the line array up above the scoreboard in the middle of a basketball arena. The top box may be aimed at the top five rows of the stadium. The box below it would be angled two degrees lower and aimed at the next five rows. The next box below that would be aimed at the next five, and all the way down," he says. "It's that specific."

Distributing speakers in strategic locations — underneath a baseball stadium's upper deck, above each seating section, for example — is a potentially costlier approach in terms of installation, hardware and wiring requirements, but there are advantages to keeping the sound source in close proximity to targeted listeners, particularly outdoors.

Says Dave Howden, director of technical services at Community Professional Loudspeakers, "Rather than projecting sound hundreds of feet from a scoreboard before it gets to the first ears, you have reduced to some degree how much Mother Nature can interact with that sound."
 

Sound may be affected by atmospheric variables outdoors and hard surfaces indoors. [Photo courtesy of Danley Sound Labs]

Outdoor obstacles
Indeed, sound designers must account for atmospheric variables such as temperature, humidity and wind when delivering sound outdoors and over significant distances.

"As you're sitting in your living room and listening to a nice piece of music — and you have some really high frequency, some nice timbre going on — it's not really difficult to deliver that at six or eight feet," Welch says. "But when you're talking from one end zone to another end zone, getting that high frequency across there is very difficult."

Sound travels at 1,130 feet per second at 72 degrees Fahrenheit, but speeds up or slows down by a foot per second for every degree the air gets hotter or colder. Still, that's not as much of a sound-delivery concern as different temperature layers within the air, for example, over a football field separating the listener from a scoreboard 500 feet away. "Hot air rising will tend to bend the higher frequencies in the voice band upward," Howden says. "That sound is still there, it's just over people's heads."

Humidity in the 10-to-30 percent range creates a dynamic known as excess air absorption. "The lower the humidity, the more the high frequencies attenuate," Howden explains, "because there's not as much moisture in the air and the atoms in the air just aren't close together."

This can be combatted to some extent by boosting the system's high-frequency drivers, but Howden offers a caveat. "You have to remember, if the humidity goes up, you don't want it to feel like ice picks in people's ears," he says. "It's a real balancing job for the person commissioning the system. With most things being computer-controlled, there are systems that allow you to select 'Is it dry out?' or 'Is it humid out?' You can provide extra equalization to offset excess air absorption more easily and more effectively."

Wind is an even more fickle adversary of the sound operator. If it's blowing toward a speaker, it too will bend sound upward, says Howden, adding, "If you have wind blowing from behind the speaker going toward the people and it's cool out, it will generally bend the sound downward and the sound will end up skipping across a cooler, horizontal column of air."

Even in ideal conditions, synching on-screen lips to sound is an exercise in compromise. "A bigger problem with patron engagement — getting them to pay attention — is if lips are flapping and the audio is not matching the video," Howden says. "People will tune out pretty quickly because it's just really annoying to watch. They might be getting sound a half-second after they see the image. But you can do calculations. 'Okay, we want the sweet spot to be the high-end seats between the 40-yard lines.' So we synchronize the video so that over about a 40-foot-wide area, everything happens at the same time there. People closer to the source are going to get the audio a little bit earlier, and people farther away will get it a lot later. We have a tolerance of about 30 to 35 milliseconds eye to ear before we become totally disengaged."

Add weather, and you get double jeopardy. "It's complicated outdoors, which is why we like to keep the speakers close to the target audience when budget permits," Howden adds. "You start trying to project sound farther, Mother Nature gets involved, especially in low-humidity environments. We can combat it some, but Mother Nature always wins."
 

The sound system and the acoustics of the space become very important to ensure that the speech intelligibility index can be measured and meets a certain criteria. [Photo courtesy of Danley Sound Labs]

Indoor considerations
Obviously, the indoor arena environment is more controlled, but it still requires forethought of design and maybe a game-day tweak.

An arena has more hard surfaces (walls, a ceiling), and thus a greater risk of reverberation. Sound hitting a wall behind a listener will give that individual two versions of the same sound a split second apart. "The room acoustics run the gamut from excellent to really bad," says Dan Palmer, head of integration at L-Acoustics. "Acousticians are skilled in profiling, modeling and fully understanding the acoustic characteristics of these venues and have some very effective tools for optimizing room acoustics to provide better speech intelligibility while enhancing the experience for fans."

Hard surfaces can be treated to absorb sound rather than reflect it. Unfortunately, such treatments can be among the first specifications cut from a bloated construction budget. "You may have a very tall ceiling, but if that ceiling is not treated at all and everything is just a hard surface, the sound has nowhere to go but to bounce," Welch says. "As it bounces it creates echoes. When those echoes arrive at your ears, they can muddy up the sound, which decreases speech intelligibility and affects even music."

This underlines how important it is to get sound design right in the first place. Says Palmer, "If we put the sound coverage in the seats instead of the walls, ceiling, floors and other acoustically reflective areas, we minimize the number of unwanted reflections in the room, making the room easier to control."

But even seating areas present variables, depending on occupancy. And unlike most outdoor stadiums, an empty indoor arena seat may be either upholstered or bare molded plastic.

"Obviously, if every seat is occupied by a large bag of water — a human being — that's going to be pretty absorptive. A bare seat is going to be reflective. A padded seat will be somewhere in between," Welch says. "An experienced operator running the sound system's mixing console can, number one, adjust levels depending on the ambient noise of the crowd and, two, use presets where the equalizer is adjusted slightly depending on the venue's occupancy or the set-up of the venue. One night it might be set for basketball, and then a couple nights later they may have a hockey game. Digital signal processing can do everything from turning loudspeakers on and off to adjusting levels and frequency response depending on the venue's use. But it doesn't always overcome the acoustics of a bad room. You can do a lot with computers, get a long way there, but there's also no substitute for proper acoustics."
 

Sound delivery models may include a point-source system in an end zone. [Photo courtesy of Community Professional Loudspeakers]

On the levels
According to Voss, typical crowd noise for a sporting event registers around 85 to 90 decibels. Big moments, such as a fourth-down play in football, might take the buzz up to between 110 and 115 dB. Kansas City's Arrowhead Stadium, home of the NFL's Chiefs, set the crowd noise record at 142.2 dB in 2014.

Why is this important? "You've got to be at least six dB above crowd noise level for the sound reinforcement or public address system to be heard," Voss explains. "That becomes very critical when you start getting into the factor of life safety, emergency evacuation announcements, even for the entertainment value."

Adds Welch, "If you're gathering lots of people, then communication is part of that and there may be laws as to speech intelligibility for life safety, in which case the sound system and the acoustics of the space become very important to ensure that the speech intelligibility index can be measured and meets a certain criteria for the building to pass and be open."

A Texas headphone system with pole-mounted speakers flanking the seating area [Photo courtesy of Community Professional Loudspeakers]

Sound loses roughly six dB every time the distance between speaker and listener is doubled — starting at one meter — meaning 140 dB at one meter becomes 134 dB at two meters, 128 dB at four meters, 122 dB at eight meters, and so on. And that's in a perfect world, without wind and other factors. This makes the throwing of sound a sort of imperfect math problem in the effort to keep levels above the crowd without the sound seeping heavily into surrounding areas.

A common design for high school football stadiums is to throw sound from a point source on the press box across the width of the field to the visiting team's spectators, while at the same time pointing speakers inward toward the home fans on light poles flanking the stands — what Howden calls a "Texas headphone" system. The challenge is supplying the visiting fans with intelligible speech while not bombarding neighbors beyond. "To throw 65 yards to the opposing team's seating area, I need to control that volume so that area is still only hitting at about 90 dB to get over the crowd noise," Voss says. "The problem is even when it hits at 90 dB there, it's still going to be hitting at 60 to 65 dB into the neighbor's backyard. That's the volume of a vacuum cleaner or a dishwasher. They're going to hear it."
 

"Spectator immersion," as Palmer puts it, has not only supplanted mere PA announcements, it has blown the roof off the fan experience. Voss was recently told by operators of the 5,113-seat Wings Events Center, home ice of the minor league Kalamazoo Wings, that 65 percent of the sound coming out of the arena's speakers during any given game night is entertainment-driven.

Howden — who runs the sound at all Philadelphia Eagles home games, about 20 Phillies games a season, as well as the occasional Villanova basketball game — relishes having his finger on the fader, as well as on the pulse of the sports sound industry.

"I run levels up and down, whether it's a simple advertisement or the opening video and we're making people's beers foam over with maximum audio level for that 30 or 40 seconds the team is running out onto the field or court," he says. "It's like a DJ plays the right music for the moment. It's my judgment how loud it should or needs to be to achieve the desired impact or engagement. That's up to me. It's fun."

Palmer, likewise, is pumped. "I'm excited about the growth in sports venue sound and the fact that venue owners and sports franchises are, more than ever, committed to getting it right — and making sports and concert events all that they should be from a sound perspective."

This article originally appeared in the April 2018 issue of Athletic Business with the title "Sound delivery keys the immersive spectator experience." Athletic Business is a free magazine for professionals in the athletic, fitness and recreation industry. Click here to subscribe.