The $100,000 Sound System Nobody Can Understand
Why spending more on commercial audio doesn't guarantee intelligibility.
By Merry Grant, Founder & Principal
Illustrative headline amount; not the documented cost of the stadium example.
The short version
- Loud and clear are two different things. A system can be plenty loud and still turn every announcement into mush.
- What makes speech understandable comes mostly from design: where the speakers go, how they're aimed, timed and tuned. The price tag and the brand name don't decide it.
- Before you approve an expensive audio proposal, ask how the designer knows the words will be understood in every seat. A good proposal can answer that in plain English.
A stadium full of echo
A school called me needing help with their stadium sound. The best way I can describe what they had: a stadium of echo.
The speakers had been placed on both sides of the field, facing each other. So every seat heard the announcer twice. First came the speakers nearby, then the speakers across the field a beat later, after that sound had crossed the whole field. Two voices, a split second apart, saying the same words. The echo was brutal.
Here's the part that matters most. If lightning's about to roll in, if someone collapses in the stands, or if the bleachers need to clear in a hurry, that same voice has to be understood the first time. That isn't a nice-to-have. That's the job.
The fix didn't start with more money or more equipment. It started with where the speakers were and which way they pointed.
There's more than one way to solve a problem like that. Sometimes a digital signal processor (DSP) helps align sound from different speakers. Sometimes a better choice is placing and aiming speakers so the sound reaches the audience from a more useful direction. The right approach depends on the field, the seating, and the problem you're trying to solve.
That's the real lesson. A digital signal processor can be an important part of a properly designed system, but it cannot replace thoughtful loudspeaker placement. Sometimes the solution requires sophisticated processing. Sometimes better speaker selection and positioning can eliminate unnecessary complexity. The right answer starts with understanding the problem, not choosing the equipment.
Loud and clear are two different things
Loudness is how much sound reaches your ears. Intelligibility is how many of the words survive the trip. (Intelligibility is just the industry's ten-dollar word for "Can you understand it?")
Try this at your desk. Say "fine" and then "sign." Now say the letters "F" and "S." The whole difference lives in one quick, quiet, hissy sound. Take that sound away and you're left with "-ine" either way.
That's how speech works. Vowels carry most of the power in your voice. Consonants, the s, t, k, f and p sounds, carry most of the meaning. They're also the first thing a poorly designed system smears.
So when the announcer says the game is delayed "fifteen" minutes and half the crowd hears "fifty," nobody is being dense. The system dropped the consonants.
Turning it up won't bring them back. If the words are smeared, more volume just gives you louder smear. And now the neighbors are calling the school board, too.
Why the music sounds great and the principal doesn't
Music is forgiving. You already know the song, so your brain fills in whatever the system drops. A big bass line and a drumbeat can sound fantastic even while they're bouncing off everything in sight.
Speech gets no such grace. Nobody knows what the principal is about to say; that's the whole point of saying it. Every word has to arrive clean, or it's gone.
That's why a demo can fool anybody. Play a favorite song through a big system with a couple of subwoofers and it feels like money well spent. But subwoofers handle the deep rumble, far below the range where speech clarity lives. They can make a demo feel like a million bucks and do next to nothing for the principal's voice.
Where the words get lost
When a stadium system can't deliver a clear sentence, it's usually a handful of things stacked together. Here are the big ones in plain English.
1. Not every seat is actually covered
Speakers work less like lightbulbs and more like flashlights. Each one throws sound in a particular shape. Seats inside the beam get clear, direct sound. Seats outside it get leftovers: echoes and spill from somewhere else.
A system can be loud everywhere and clear almost nowhere if the beams don't land where the people are. The visitors' side, the far end zone, the track and the concession line all need someone to decide they matter and aim for them on purpose.
2. The timing is off
Sound is slower than most people think. It travels roughly 1,100 feet per second, about a foot every thousandth of a second. Across a stadium, that's slow enough to cause trouble.
If you're sitting between two speaker locations, or near a big hard surface like a press box, the same word can reach you two or three times, a split second apart. Your ear blurs them into one mushy word. If you've ever heard an announcer seem to say everything twice ("Now batting … batting … batting"), you've heard timing go wrong.
That's the stadium from the top of this article. Good designs consider where sound comes from, how the speakers are aimed, and whether electronic timing (called delay) is needed. When speakers face each other across a field, delay alone may not solve the problem for every seat. Where the speakers go comes first.
3. Nobody planned for the noise
A stadium on game night isn't a quiet room. The system is competing with a cheering crowd, a marching band, wind and maybe a highway. Speech has to sit comfortably above all of that to be understood. A design checked against an empty stadium on a Tuesday afternoon hasn't really been checked.
4. The space itself is fighting back
Hard surfaces bounce sound: concrete, metal bleachers, brick, glass. Outdoors, that bounce is mostly a timing problem. Indoors it's worse. A gym is basically a big drum made of block walls and a hard floor, and sound can hang in the air for seconds. In a room like that, adding speakers can make things worse. Sometimes the right fix is treating the room with sound-absorbing panels instead of buying more equipment.
5. The microphone, and the person holding it
A six-figure system can be undone by a bargain microphone, a mic held at belt-buckle height or an announcer who was never shown where to stand. That's nobody's fault. It just has to be planned: the right mic for the announcer's spot, and a short training session for the people who'll use it.
6. Nobody tuned it
New equipment arrives as a box of potential. After it's installed, someone has to set the levels, the timing and the tone so the system works in your space. That's tuning. Commissioning goes further: it's the process of checking that the installed system performs as intended, documenting the results, and confirming it's ready for the customer to use. Ask who is responsible for each step and whether it's included in the price.
Can you put a number on "clear"?
You can. The most common yardstick is the Speech Transmission Index, or STI. It's a score from 0 (nobody understands anything) to 1 (perfect). A designer can predict it with modeling software before anything is bought. It can be measured with a meter after the system is installed.
NFPA 72 includes intelligibility guidance for emergency voice/alarm communication systems, but those requirements don't automatically apply to an ordinary stadium PA used for announcements, music, and sporting events. If the PA also serves as part of the venue's required emergency communication system, the applicable code and performance requirements need to be established before the system is designed.
Not every project needs a full computer model. But every proposal should be able to explain how the designer knows the words will be understood, seat by seat.
Why the brand name isn't where to start
My grandma's cast-iron skillet makes the best cornbread. I like to joke that it's the love and care that's been put into that skillet. Whatever it is, the cornbread comes out perfect every single time.
Audio works the same way. The brand name on the box is just the skillet. What makes it work is the care that goes into the design: the right speakers in the right spots, aimed the right way and tuned for your field.
When a proposal leads with brand names, it's answering "What are we buying?" before anybody has answered "What are we trying to do?" Those questions belong in the other order:
Maybe the school across town has a fantastic sound system, and you want the same one. That's understandable. But their field, seating, installation resources, and operating needs may be completely different from yours. The goal isn't to duplicate their equipment list. It's to achieve the results you admired in the first place.
- Who needs to hear what? Fans, players, the band, the track, the parking lot?
- Where will they be sitting or standing?
- What are we competing with? Crowd, wind, band, traffic.
- What has to happen in an emergency?
- Who's on the other side of the fence? Neighbors appreciate it when the sound stays in the stadium.
Once those answers are in writing, choosing equipment gets a lot simpler. Planning before you race to purchase can save time, headaches and money. You can also tell whether a high price is buying clarity or just horsepower.
The people who can't hear it at all
Assistive listening is the part of audio I'm most passionate about, and it gets missed often.
Think about the people in your stands, at graduation, or in the back row of the school concert who can't make out the words. A student, a parent, a grandparent, a teacher. Many of them sit and patiently endure the event. Endure, because they aren't enjoying it.
I don't believe people with hearing loss get set aside out of ill intent. Most of us simply don't know what it feels like to not hear properly. A free online hearing loss simulator changed that for me. It helped me understand my own grandmother's needs when others couldn't, or didn't. If you've never tried one, give it a few minutes before your next audio decision.
An assistive listening system sends the announcer's voice straight to a small receiver and earpiece, or directly to a person's hearing aids. The echoes and crowd noise drop out of the picture. And here's the good news: it can be added to almost any existing sound system. It doesn't have to wait for a renovation.
It's a requirement, and it's more than that
The 2010 ADA Standards for Accessible Design count stadiums and grandstands as assembly areas. Section 219 generally requires an assistive listening system in assembly areas where audible communication is integral to the use of the space. Under the 2010 ADA Standards, assembly areas without audio amplification generally qualify for an exception to the assistive listening system requirement. Courtrooms are treated differently and do not qualify for that particular exception. The standards also address receiver quantities, hearing-aid compatibility and signage.
How those rules apply to your facility is a question for your architect, your local code official or your district's ADA coordinator. I'm not a lawyer, and this isn't legal advice.
Requirements for existing facilities can differ from those governing new construction or alterations, so the applicable obligations should be confirmed for your particular facility.
Compliance is the floor, though, not the goal. A responsible designer should raise assistive listening whether or not you asked, and help you see who gets left out when it isn't there from day one. If a stadium sound proposal doesn't mention it at all, ask why.
Before you sign: ten questions to ask
You don't need any technical language to ask these. You just need to ask them, then listen for whether the answer is plain and specific.
| Ask this | Why it matters | A good answer sounds like |
|---|---|---|
| What problem is this system solving, in plain words? | If the goal isn't written down, nobody can check whether it was met. | They restate your goals: clear announcements in every seat, music for games, emergency messages. |
| Will every seating area get clear speech, including the visitors' side and the track? | Loud everywhere isn't the same as clear everywhere. | "Here's a coverage map showing each area and which speakers serve it." |
| How do you know the words will be understood? | This is what separates a design from a shopping list. | A predicted clarity score (STI) for the seating areas, or a clear explanation of how they checked. |
| What noise did you design around? | A design checked against an empty stadium hasn't really been checked. | Crowd, band, wind and nearby traffic, named specifically. |
| What happens on the other side of the fence? | Sound that spills into neighborhoods turns into complaints. | A plan for aiming sound into the stands and away from homes. |
| Who will operate this system, and what happens when that person leaves? | A sophisticated system should still be manageable for everyday users and their successors. | Simple controls, training, written instructions, settings backups and a support contact. |
| What microphone will the announcer use, and who trains our people? | A great system can be undone at the microphone. | A specific mic for the announcer's spot and a short training session. |
| Where's the assistive listening system? | Accessibility requirements can apply, and people with hearing loss are in your stands. | Included, with receivers sized to your seating, plus signage. |
| How will we know it's finished and working? | "Done" should mean "understood," not just "installed." | A walk-through test of the seating areas before final payment. |
| Why this equipment and not something less expensive? | Every major item should have a job. | Each big item tied to a specific need, not "it's the best brand." |
A good vendor will welcome these questions. Plenty will have the answers ready. Sometimes the answer exists and just never made it onto paper, and asking is how it gets there.
Words worth knowing
- Intelligibility: how much of what's said can actually be understood.
- Coverage: which seats a speaker reaches with clear, direct sound.
- Delay: electronic timing that lines up sound from different speakers so it arrives together.
- Reverberation: sound that keeps bouncing around after the words are spoken. Lovely for a choir, rough on a principal.
- STI (Speech Transmission Index): a 0-to-1 score for how understandable speech is.
- Tuning: adjusting levels, timing and tone after installation. Commissioning: checking, documenting and confirming the installed system performs as intended.
- Assistive listening system: equipment that sends the PA straight to a receiver, an earpiece or a hearing aid.
Have questions about your stadium sound system?
Understanding what you need is the first step toward finding the right solution. If you'd appreciate an independent perspective, Rebel Herd Media is available to help.