Large Venue Acoustics

Large venues like amphitheaters and stadiums are used across the world for a variety of purposes, hosting everything from sporting events to concerts to large social gatherings and other events. The massive size of the spaces, alongside their multifaceted uses, however, mean their acoustic needs are quite different from those of smaller rooms or even concert halls. This episode, Gary W. Siebein (Siebein Associates, Inc.), Keely Siebein (Siebein Associates, Inc.), Jack Wrightson (Wrightson, Johnson, Haddon, & Williams, Inc.), and Joe Solway (Arup) discuss the unique considerations for designing these structures. 

Read the associated article: Gary W. Siebein, Keely Siebein, Jack Wrightson, Joe Solway, and Raj Patel. (2024) “Large-Venue Acoustics- Arenas, Stadiums, and Amphitheaters,” Acoustics Today 20(1). https://doi.org/10.1121/AT.2024.20.1.55.

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Intro/Outro Music Credit: Min 2019 by minwbu from Pixabay. 

Transcript

ASA Publications (00:24)

Today we're going to delve into the world of architectural acoustics, but not in terms of rooms or even concert halls. We're going to be discussing the acoustics of really big structures like stadiums and arenas. With me are Gary Sebein, Keely Sebein, Jack Wrightson, and Joe Solway, who co-authored the article, “Large Venue Acoustics” Arenas, Stadiums, and Amphitheaters,” which appeared in the Spring 2024 issue of Acoustics Today. Thank you all for being here with me today. First, tell us a bit about your research and practice backgrounds.

Gary Siebein (00:54)

Sure, I'll start. Gary Siebein. I was a professor at the University of Florida School of Architecture for over 35 years. I had a graduate program in building and environmental acoustics that I directed, with a laboratory there conducting research to measure, model, simulate, predict acoustic qualities as they're perceived by people in complex buildings. We developed equipment modeling methods, survey techniques, simulation methods to assess acoustics. And then the university was gracious enough to allow me to run a practice while I was a professor, so then we transferred these techniques to use in everyday buildings of all types in our practice, from schools and colleges, to military and law enforcement, to hospitals, research centers, theaters, performance halls, museums, and just about every other kind of building you can imagine.

Keely Siebein (01:44)

I can follow. I'm Keely Seabine. I am a principle at Siebein Acoustics as well. I have performed research on acoustic standards, classroom acoustics, restaurant acoustics, animal facilities, healthcare acoustics, and all kinds of soundscape research as well. I've worked on over 500 projects and I have co-authored five books and book chapters and have been invited to present papers nationally and internationally at professional conferences. And I also guest lecture at the University of Florida in interior design and architecture classes, as well as present continuing education for many different participants, architects, engineers, interior designers, etc.

Jack Wrightson (02:31)

I have a little bit different background from a lot of people in this business. I started out my academic acoustical studies as  as undergraduate, when in independent research did an acoustical study that ended up being, unknown to me at that time, a replication of a critical band study on hearing. But going into graduate school, I worked in the acoustics lab as a research assistant at the University of Wisconsin, Milwaukee. And I was co-author on several papers there. And unlike a lot of people, three and a half years through it, I dropped out. I went into private practice. So I'm a graduate school dropout. Did get a master's, went beyond that, but didn't finish the doctoral program. And the reason why is that  I had become more and more interested in applied acoustics rather than purely theoretical stuff and wasn't sure I wanted to do, all respect to Gary, a purely academic route all the way down the line. And so went into work in private practice, moved to Texas, joined a consulting firm there, continued to do some research. Although because that's all  applied things, the papers then went from purely theoretical,  perceptual  into more practical acoustic things. Authored some recording studio control room acoustics articles for the Audio Engineering Society, have given several papers at ASA meetings as well as done a couple of invited talks for national ASA meetings as well. So, formal research after that point, it's mostly how am going to figure something out and get it done, but from the formal stuff that's pretty much my background. And I've been working mostly in large venue acoustics, arenas and stadiums and entertainment facilities, starting in the late 80s and I have also served as adjunct professor of architectural acoustics at University of Texas Arlington.

ASA Publications (04:16)

I mean, the practical stuff is very interesting to hear about too, you know, the practical experience at least. And Joe?

Joe Solway (04:24)

So great to be with you,Kat, and everyone here. So my background is in physics and… part physicist and part frustrated musician, which I think is many, many acousticians’ beginnings, perhaps, and started then went to study acoustics and then started with Arup back in 97. So just over 28 years ago, I joined as a young graduate. And Arup is a global consulting and engineering firm, but we have a specialist acoustics and AV and theater consulting team, which I now help lead in the Americas and focused for most of those 28 years on the designing of performing arts and entertainment and sports spaces.

ASA Publications (05:06)

Awesome. So what makes large venue acoustics different from regular room acoustics or even concert hall acoustics?

Gary Siebein (05:13)

Jack, do you want to start off with that?

Jack Wrightson (05:15)

Yeah, I'll go ahead and start with that. So there's a couple ways to look at it. One of the ways I like to explain this to people is when you walk into a space, and you look at it, your initial impression is basically what your eyes tell you. And then you start listening to it. And one of the things is light moves very quickly. We walk into a big space, we look into a small space, we look at the materials, we get finishes, the colors and stuff. It doesn't seem that much different than a little space does. It's just bigger.

On the other hand, by comparison, sound moves very slowly. And the interaction of sound moving around in the space and reflections we hear and everything else changes dramatically between a big building and a little building. So for example, when you talk about the concert hall example, concert halls, in order to produce the sound that people want from a concert hall, let's call it an acoustic symphonic hall for want of a better example-- it needs to be a particular size, a particular shape to provide the sound reflection patterns, the reverberation times and everything that is appropriate for the music being played in that venue. Once we get into a stadium and arena, we're not so worried about the subtleties of the natural acoustics in the space because 99.9 % of the time all of the music, speech is amplified. So we're looking at a space which is more receptive to a sound system than it is to acoustic instruments like they would be in an opera house or a concert hall. So the rules for that go out the window and now we're worried about what are the rules to make the sound systems sound as well as they can. There are also concerns having to do with, know, crowd noise, intensity of crowd noise, it's loudness and stuff. But they're fundamentally different buildings being used for different purposes in different ways. Joe, do you have some comments on that?

Joe Solway (07:05)

Yeah, I mean, absolutely agree with you, Jack. You know,  when we're designing concert halls, we're very much thinking about the reflection of surfaces how the shape of the architecture informs what you're hearing in the space. But as soon as we move into larger spaces that are used with purely amplified sound, then we're often looking to eliminate a lot of the natural acoustic in the space and then making it work for the sound system alone.

Gary Siebein (07:33)

Well, and in these big spaces because there are so many, so many people, and they're so large, they also have very large air conditioning systems and building service systems that need to be taken care of for noise and vibration control compared to a normal size building. And I think we've seen in recent years, really expanding the audio and video systems in these rooms to create more immersive kind of surrounding environments as opposed to just trying to direct sound from a point source speaker to an audience to hear announcements, say, in a basketball arena or something.

ASA Publications (08:14)

Okay, so there's a lot of things to consider. What are some of the standard considerations of room acoustics that hold true for large venues as well as small ones?

Joe Solway (08:24)

So, you know, we can think about, you know, there were three aspects to acoustics. Obviously, there's the background noise systems, the HVAC systems, which apply to any space you’re in. There's the issues of sound isolation, which also apply to any kind of room. But when you talk about, when you get into room acoustics, then as soon as you move into very large spaces, for sound, then the natural voice or the unamplified speech or unamplified music doesn’t have the power to excite the room that it would in a smaller room. So as soon as we move into a large stadium or arena, then the way that it responds to unamplified speech or music is very different to when you begin to put in the amplified sources with a lot more sound power that have the ability to then excite the room.

Jack Wrightson (09:16)

Another way to look at this, that basically amplifies what Joe was saying, is that the materials, all the standard acoustical considerations apply. Reverberation time, sound reflections, noise, as Gary pointed out, from HVAC and other mechanical systems. All that stuff still applies. The difference is, and materials and considerations, all that applies. The difference is the time domain aspect of it. So as Joe pointed out earlier, the sound reflections, all the reflecting surfaces are much farther away. So the reflecting surface pattern, the energy time curve, the echogram, whatever you want to call it, the impulse responses, is very, very different in a big room than a small room. And it changes how you need to apply all those standard acoustical techniques, tips, and materials.

ASA Publications (10:05)

Okay, so because it takes longer for the sound wave to get to the edge of the room…

Jack Wrightsonl (10:10)

And then come back.

ASA Publications (10:11)

And then come back! Yeah, it throws off all of the calculations, okay. 

Jack Wrightsonl (10:15)

Yeah, so it's a fundamentally different space for that aspect. But you still need absorption. You're still worried about reverberation time. You're still worried about echoes and all those things like that. It's just that the scale of it changes how you think about it.

Joe Solway (10:31)

And because those surfaces are so much further away, whereas in a smaller room if you get a reflection off say an untreated bit of wall, you may not perceive that as a discrete echo. As soon as we get into larger spaces, then if you, especially when you have a heavily treated room, if you have certain surfaces that aren't treated, then you have to pay special attention to making sure you're not getting some slap back of sound that's creating a discrete late echo of sound that's really going reduce the clarity and the intelligibility in the room.

Jack Wrightson (11:03)

Yeah, for example, the standard small room reverberation time calculation really starts to fall apart a bit in a very, very… say in a dome stadium. So one of the things that we developed, and we did an invited ASA paper on this a number of years ago, one of my former partners and I, Jim Johnson and I, we had developed a correction for very large spaces, which basically involved the mean free path, which is the average distance that a sound takes from the source, be it a speaker or a spectator, whatever it may be, to the nearest reflecting surface. And then basically made a division with the mean free path over X. Then we applied a distance loss calculation reduction, because the energy is reducing off stuff like that, which means that the energy coming back on the reflective surfaces less than the standard reverberation time calculations would predict. So it's basically a correction just based on air loss and distance loss for the fact that the room is so big.

Gary Siebein (12:02)

Yes. The sound transmission is also important, whether these are standalone buildings like the dome stadium that Jack mentioned, or whether it's an arena or a large performance venue that is within a mixed-use building, because with a large audience, you're playing very high sound levels that will then propagate out of the arena or the stadium, either to adjoining properties or other uses in the building. And so the kind sound isolation design of these buildings becomes very important.

Jack Wrightson (12:34)

You know, Gary, you make a very good point. And, Kat, if we can jump down to the that question says, “Do the fact that indoor stadiums and arenas solve a community noise problem?” because I think Gary's comment leads you right into that. And as Gary points out, no, they don't. 

ASA Publications (12:50)

Yeah.

Jack Wrightson (12:50

Are they better than an open air venue? Absolutely. But they don't. And one of the reasons why is, especially for the roof, and Joe can amplify this with his work at Barclay Center, that the roofs are fairly low-mass structures. We have very, very large free spans there. It's a structural consideration that whether the roof is heavy or not. And then we also have, we started out with dome stadiums that were fabric roofs because they were air supported. Very few of those left anymore. And now the architectural trend is to use ETFE, which is basically a plastic bubble, which doesn't have much more mass than the old air-supported structures. So we have all these basically plastic roofs in a lot of these new NFL stadiums which have very, very low transmission loss characteristics. So there's a lot of places in the building for sound to get out and the levels, as Gary pointed out, are high enough that it is concerning when you have nearby sensitive properties.

ASA Publications (13:53)

Okay, okay. Yeah, I think let's save some of the going into the nitty gritty of the community noise issues for a little bit later, because I want to do more of the overall view points first, but you make really good points there. So what acoustical issues arise specifically for large venues, and why are they of concern?

Joe Solway (14:14)

So I think we’ve touched on some these: that, you know, you have large volume, so the reflection sequences that you're getting back are very late. So thinking around the potential for echoes in those spaces, the issues around how do you adequately control the reverberance in them. And one of the issues is, when we think about the acoustics in the room, we have to think around the sound systems that in these rooms too. And certainly in the last 20, 25 years, we've seen a growth of sound systems that have a lot more energy at the very low end, so the 40, 50, 60 hertz energy, compared to systems from 30 plus years ago. So having a room acoustic solution that can adequately control and reduce the reverberance at the low end is important to avoid a really muddy  sound in space. And of course, the challenge is if you have an absorbing material, as your standard, say, two-inch, four-inch thick absorbing material, it's very effective at mid and high frequencies. But when you think around the bottom end of that music source, at 50 hertz, then you've got a wavelength that's 22 feet. It's got a quarter wavelength of five and a half feet.

So a one or two inch thick sound absorbing material isn't going to do a lot down at 50 Hertz. So finding material and architectural solutions that can provide you good, effective absorption down at low frequencies is important to consider from the beginning.

Jack Wrightson (15:46)

Yes, correct. And it's very important, typically more important in arenas. They do many more concerts than do dome stadiums, but it still applies. One of the things that we've done to try to get at the low-frequency absorption problem is exploit architectural voids and create a, as colloquially known as a bass trap, which do have those interior volumes that Joe was talking about, so the bigger the better. You can trap the lower wavelengths in. And they've proven to be pretty successful in a lot of arena projects. So that's one of the differences.

ASA Publications (16:17)

Can you explain what that is a little bit more? What that idea is?

Jack Wrightson (16:20)

Yeah, so basically if you… there's the classic example of amplifying low frequency absorption over and above just what you would predict from having it be X number of inches thick on a flat surface by putting it in a corner. You put it in a corner because sound, once again, colloquially put, piles up in the corner it makes it more efficient, given its area.

What we tried to do with the arena bass traps is we find architectural voids, whether they're above ceilings, high in the roof, or something like that, and we create a void, and we basically trapped it off with a semi-transparent material. So it might be it's something that has a fair amount of flow resistance, so maybe, you know, a couple inches of inches of fiber glass, as the face to the open void, so it scrubs off some energy on the way in. It rattles around inside the void. We have sound absorption in there that does that, and then it has to come back out. So what happens is you're losing a fair amount of sound energy getting into the bass trap, within the bass trap, and then exiting the bass trap, which knocks it down. The bass trap is big enough, to Joe's point on the wavelengths, that it is able to have half or quarter wave distances, be efficient at low frequencies compared to just surface mounted absorption.

ASA Publications (17:38)

Then you were going say something else before I interrupted you.

Jack Wrightson (17:39)

Yeah, I was. A lot of these buildings, and this is becoming less common, are multi-purpose facilities. Most of them start out as sports facilities that, hey, this is a big space. We can put a lot of people in here, and let's have a concert as well. Well, obviously the concert business is well developed in stadiums and arenas over, you know, 50 years at this point. But we're saddled with things that are for sport.

So the sports, the seating is designed for sightline, not for acoustics. We have lots of glass railings in these buildings now, that are sound reflective, that are put in for sightline reasons. We have lots of LED displays, which are sound reflective. And so there are a lot of things that we worry about that we can't do a whole lot about because sports is a primary function of the space.

Some of these buildings, and there's more being built, are primarily concert spaces these days because the concert business is big enough in some markets that they can build a 15 or 20,000 seat place that doesn't need a hockey or a basketball team to be economically successful. And so those will do away with the glass railing and things like that. And they don't need LED displays and scoreboards and things like that. So they can be much more attuned to just that amplified music performance that Joe was talking about.

In dome stadiums, one of the things that's very, verry different, and that we run into this as a challenge all the time is, is just a sheer scale of it. So one of the most effective places to put sound absorption in an arena or a stadium is on the roof, because we often aren't competing for lots of other, you know, jobs or functions that that surface has to do. It's basically a surface we can get access to. But in a dome stadium, we're talking about acres of area. We're not talking about square feet. A dome stadium can have three or four acres of roof area. And so you start talking about adding acoustical treatments, effective acoustical treatments to roof area. That's, let's say it costs a couple to three dollars a square foot, something relatively inexpensive. Well, once we start multiplying that by acres, we're talking real money as the joke goes. So we run into budget concerns on that. And there are a number of dome stadiums where they have rejected doing as much acoustical treatment as they conceivably could have, just because it was a budget consideration. And a lot of the appearance, they figured they didn't need it to play football, for example. So does that affect concerts? Yes, it affects concerts. So dome stadium concerts aren't considered to be, you know, the epitome of the best possible amplified music experience, to be kind about it.

ASA Publications (20:20)

Hahaha

Jack Wrightson (20:21)

So there are things that are not acoustical in nature, that actually affect what you can do acoustically. And I think all of us have run into that budget consideration or aesthetic consideration or something like that, which sometimes puts a damper on the acoustical goal.

Joe Solway (20:39)

And to add to Jack's comments around the thinking around cost, I think a challenge at the beginning of the project is working with a structural engineer on minimizing the curvature of the roof. So often the most efficient way for a structural engineer to design the roof of one of these spaces is to do a convex form where it’s very efficient structurally, but you're adding a lot of extra volume to the space potentially. And of course, reverberation time is, reverberation is proportional to volume. So the more volume we add to the space, the higher the reverberance and therefore the more absorption we need to try and control the acoustic. If we can work with the architect and the structural engineer from the outset of the project, and say, can we have a flat roof or even could we go with a concave roof? And then try and minimize for the extra volume in the space, then that helps us reduce the amount of absorption we need in there, which then obviously has knock-on impacts for the cost, as Jack was outlining.

Jack Wrightson (21:41)

In addition to cost, other problem we've had in dome stadiums, the last generation of dome stadiums have all put an architectural premium on letting natural light into the seating bowl. And so I was talking about ETFE roofs, which are always translucent or clear. Examples of that in Atlanta, Las Vegas, Los Angeles, and also in Indianapolis and large glass indoors and Minneapolis and places like that. And also the new one in Nashville. So with this premium on natural light, it's kind of hard to put acoustical treatment over the clear portion of it. So it takes surface area that you would like to use acoustically, sort of out of the equation in order to achieve this architectural goal of allowing natural daylight into the building. So that's another challenge that we have to deal with. And it's hard to make that up.

Joe Solway (22:31)

And of course, those lightweight roofs are great because they're so thin and they have so little mass. They're actually good for low frequency sound absorption because effectively the low frequency sound is going straight through them. But you still then have the issue of that mid-high frequency sound that is getting reflected back into the space that you need to deal with.

ASA Publications (22:51)

And how do they affect, I mean, I know we're going to talk about noise later, but how will those really thin roofs, how do they affect noise absorption for out to the community?

Joe Solway (23:03)

So exactly that. Well, compared to, as Jack was saying, compared to something that's open, then it's better than nothing, right? But you still have a lot of low frequency sound just going straight through that lightweight membrane, that it could be disturbing to the surrounding community.

ASA Publications (23:04)

Okay.

Keely Siebein (23:21)

Just kind of chiming in as we're talking about the finishes, I was in an arena last weekend and was noticing that there was about three inch thick, kind of fibrous acoustic material on the walls, and was thinking about the idea that the types of finishes in these large scale arenas maybe have to be a little bit different than the types of acoustic finishes that are used in rooms that are smaller or less people around. So just wanted to see what your thoughts were on, I know we were talking a lot about the ceiling, but there is usually some potential on some of the wall areas and wanted to see what your thoughts were on some of the finishes that you have found successful. Not necessarily naming names, but just types of finishes and durability and whatnot.

Joe Solway (24:17)

Yeah, as Jack was saying earlier, I think when you can have that same sound absorbing material, but instead of putting it directly on a surface, but if you can have a good airspace behind it, and maybe it's a wall, maybe the wall itself is just a sound absorbing material. We’ve done arena spaces where we've had, effectively the wall to the arena just be the sound absorbing material, and then the corridor space, the circulation space, acts as that additional cavity that you need to give you low frequency absorption. So either in the ceiling or in the walls, finding to extend that absorbing material and improve its low frequency absorption.

ASA Publications (24:53)

So how do acoustical considerations change when you have outdoor venues?

Gary Siebein (25:00)

The outdoors become very interesting. So back when I was a young guy, I went to one of the first large outdoor performances at Woodstock, upstate New York. And it was located out in a guy's farm field, and thousands of people came. And you could gather there and park in the fields, and there were really minimal impacts on large numbers of people other than those who were associated with the event. I don't know that there are that many greenfield, kind of open air places where you can situate a large performance venue anymore, so careful selection of a site to accommodate a facility in terms of its sound footprint, so to speak, becomes really important when it's near centers of population that can fill it up basically. You know, these start, I grew up in New England and we would have a bandstand on the village green going back to the late 1700s, early 1800s, in a lot of these old towns in Connecticut and Massachusetts. And, you know, you'd get a little group to perform on the bandstand or have the selectmen for the village come and talk to people at a July 4th picnic or something. And it was the whole town would gather and participate in these.  Today’s facilities are not little bandstands on the village green anymore. I mean, you know, they're very large facilities. Some of them with partial covering or partial enclosures over kind of prime audience seating with an extended lawn area out behind them. And to control the propagation of sounds off-site to adjacent properties from the large amplified sound systems to convey sound to thousands of people becomes a real challenge, especially where they're confined in or located in built-up areas. I know a lot of the team members on projects for this have to deal also with the of incoming and outgoing traffic to bring the large numbers of people in and out, to park vehicles or have transit service them. Just the circulation of large numbers of people coming in and out has potential impacts neighboring facilities. Outdoors, it's very hard to maintain acoustic quality, high quality acoustics, over these large areas. So you need multiple loudspeakers both at the stage and often with what are called delay rings or large posts going around the facility to evenly distribute the sounds over the stage. The little bandstand or a natural acoustic band shell would have surfaces oftentimes to allow natural acoustic performers, the town band or orchestra or a small performing group, to be able to hear each other and gather their sounds and propagate it out to an audience. On larger amplified facilities, especially for amplified musica, the sound monitors, you know, a lot of performers still use floor wedge loudspeakers for their monitoring on the stage, and these get thrown back against the stage walls and so all of a sudden the stage is not a reflective enclosure to allow performers to hear each other but it's a sound absorbing surface to a large extent to reduce the reflections from the monitor speakers on the stage from getting propagated out to the audience.

A lot of times these facilities don't even have their own sound systems. Many of them are built as like road houses where each different group of performers will come and bring their own equipment week by week, time by time. So you need very large load in, load out areas so the trailer trucks can come in and load out all the equipment very quickly, set them up, and large accessible utility raceways and so on to run all the wires that are needed to set up a large performance that oftentimes today will include large LED video displays that go with all the touring acts in addition to their amplifiers and communication systems and so on. If there's a roof or walls, a lot of the concerns that we had talked about earlier certainly pertain to this, that once you put these on, they become very important to be sound- absorbing surfaces, especially with regard to preventing the long delayed echoes off any built in wall, partial wall structures say that might enclose parterre seats or steps as you move back further in amphitheater or any roof surfaces that are put over all or part of seating area. So it's a very interesting and challenging venue to work in.

Jack Wrightson (29:48)

Yeah, one of the things I'd like to amplify on the community noise aspect of it is, you know, Gary was talking about large amplified sound systems. We've measured outdoor concerts and amphitheaters, even some that have walls around them, at 50 dBA at distances of 10,000 feet or more. 

ASA Publications (30:07)

Ooooh. Yeah.

Jack Wrightson (30:10)

And so when you start talking about taking a cardioid-shaped two-mile radius balloon around the facility, that takes in a lot of potential neighborhoods and areas and stuff like that. And for that reason, there are a lot of these facilities now that are in more populated areas that have developed noise level restrictions, generally at the mixing console that, you know, it's part of the contractual obligation of the act.  They cannot play over X. Sometimes the measurement points at the rear of the venue. And also time, certain curfews of how late they can go and things like that. It's all in the effort to make them more compatible with mostly residential areas that might be within that two-mile area.

Keely Siebein (30:51)

Yeah, that's a great point. You know, a lot of older established amphitheaters and open-air venues,  a lot of times their communities will have developed noise ordinances or code, procedures to kind of deal with the noise from very, very unique venues. When new venues come in, that can potentially be a challenge where, if a venue is coming into a place where there was not previously an amplified music venue, then it’s something where it would likely be helpful that the community engages in a kind of effort to do a study to basically determine what acceptable sound levels are given the kind of considerations of the site, how close the nearest residences are, what activities the venue is trying to engage in, how often they're taking place, because as Gary and Jack have mentioned, there are a number of either physical interventions that can be considered, whether it's, you know, berms or barriers or partial enclosures around some of these venues, operational procedures, whether it's sound level limits at the mix or a certain distance away, whether it's a time limit, you know, you can play till, you know, X time on Thursday, Friday, Saturday, and maybe other limits on different days of the week. But there are a number of different types of interventions that can be considered and, you know, rightfully so to try to maintain compatibility with what we're trying to achieve with the amphitheater or other venue and the environment that we're trying to also achieve in the surrounding areas. And sometimes they can be competing interests, but trying to find that middle ground of how do we allow both to be able to work together and to have as compatible relations as possible is something that's worthwhile and can be challenging but with worthwhile effort.

Gary Siebein (33:14)

In today's digital world one of the things that helps facilitate some of those discussions are active sound monitoring systems so that the guys who are running the sound at the mix have some idea not just about what they're hearing inside the facility, but what sound levels are at, you know, the nearest apartment building or neighborhood off to the south or whatever the case might be. And these are often fed also to a municipality agency so that there's kind of communication among those involved in terms the levels actually are so that there's some objective basis for having those discussions that Keely was talking about.

ASA Publications (33:57)

Okay. Well, we can get in more into community noise in a second, but I wanted to pivot for a moment and just talk a bit about a particularly large large venue, the indoor stadium with a domed roof, which, Jack, you talked about a little bit already, but your article called these “notoriously difficult.” What extra considerations must be made with the acoustics in these venues?

Jack Wrightson (34:18)

Well, they're notoriously difficult because they're very large, as we talked about. And as Joe mentioned, the reverberation time scales with the volume and in a somewhat nonlinear fashion. And so you're dealing with very large reverberation times. You're dealing with budget challenges, we pointed out, of trying to treat literally acres and thousands of square feet of surface. We have the challenge of surfaces that cannot be readily treated because they want to be transparent or translucent enough to admit natural daylight. And then we have all the sporting aspects of the building that we have to deal with, whether it's glass railing or other elements of the building that were designed to facilitate sports-- LED displays, which are reflecting surfaces pointed out earlier and things like that-- that we're trying to overcome all these things. And so what happens is when you're handed a poor hand in the poker game of dome stadium acoustics, what do you do about it? And so we, when we're limited on what we can do with acoustical materials, we can't control the shape because that's by the size of the playing surface and sight lines for how many people that are in the building, that we start worrying about the sound system when it comes to concerts. And so we're trying to have a sound system that is intelligible and good sounding for the sports event. But the concerts, as was pointed out earlier, they bring in their own systems. Every single one of these dome stadiums is a little bit different. And in the recent generations of dome stadiums, we're purposely designing the sound systems to be integrated with the touring system. And so what we'll do is we'll use loudspeaker products of a type and of a location that they can integrate easily with the touring sound system. The touring sound system guys will look at the product, they'll look at what it is, where it's placed and say, “Yep, that makes sense,” as opposed to, “You have no idea what you're doing.” So there's a lot of what I would say collaboration in terms of, you know, what's acceptable for that use and things like that. And then we design the systems that makes it easy to integrate. There's a small part of our business we have where people actually spend time on site. They'll work with the touring sound operators, model their system in the building because we already have the acoustical model of the building and they typically don’t, and then show them how their system can work better, what parts of the existing sound system will amplify or enhance the use of their system and allow them to do things to get a better overall result. What we're trying to accomplish there is keeping the direct to reverberant or direct to the reflections, or as I like to put it, direct to everything else, sound level high, that ratio high so the audience has a good chance of getting some level of direct sound dominance straight from the loudspeakers to their seating position. And hopefully that minimizes the perception of the reflections and reverberance and everything from everyone else. We can improve on that, but in these very difficult spaces, it's very, very difficult to have everyone have that high signal-to-noise ratio experience of sound dominating from coming directly from the loudspeakers.

Joe Solway (37:24)

I’ll to that, one of the key things when we're looking at the sound system is looking at the time delays in the house system compared to the touring systems that are coming in because you want to have, if, say, if you're in the upper tiers then you may not be fully covered by the touring system, especially in arenas that have much seating areas. So you're relying on the distributed house system that covers those areas, but you want to have the perception that the sound is coming from the stage. So the sound from the distributed speakers needs to arrive at you just after the sound from the main touring system. So subjectively, you perceive it as coming from the stage, even though a lot of the clarity of the sound that you're hearing is actually coming from a slightly delayed system from the house speakers.

ASA Publications (38:16)

Okay, so one running theme in this conversation so far, that we keep coming back to, is the community noise impact can arise with large venues. So why is noise control such a challenge with these structures and how do you manage it in your designs?

Joe Solway (38:33)

So you’ve got multiple things that can cause major issues. You've got, in recent years, sound systems that have much more low-frequency content, it be 40, 50, 60 hertz. You've got a trend to go to lighter weight, as Jack was saying, ETFE, PTFE roofs that have very little sound isolation quality out of it. And then something that we're really seeing now in a lot of new arenas and stadia is that they're not being designed or developed in locations that are, say, now just in a big parking lot. There a desire for building not only the arena and the stadia, but to build that commercial residential hotel components on the outside of those developments. So unlike, say ,stadia and arena from say the 80s and 90s that were perhaps located further away from residential areas, more of the stadiums that are being built today and arenas that are being built today also have, say, and residential components that are being built right up next to them. So instead of saying, “Okay, my residence is a mile away,” now they’re 50 yards away, right? So the proximity of some of these the new residential that's going in and hotels is much closer to some of these newer developments.

Jack Wrightsonl (39:51)

So when you're doing a mixed-use development and it's all new and it's covered together with a venue, the music or entertainment venue, sports venue, we can also control, to a certain extent, the design of the hotel or the residences that are part of the new development. Better windows, better roof insulation, more mass in certain areas, different wall constructions, stuff like that. And what we can do as part of a planned-use development require that they have certain inside/outside noise reduction. And there's multiple different ways to, you know, model and what metrics are used to do that. But basically what, how many dB drop you have between the two. And so, that's one way of attacking it there. The other thing, when you go into an existing neighborhood where there's existing residents and hotels and sensitive uses and we've run into hospitals and things like that where, they're, you know, the noise levels really matter. Then you start to start treating the building. And when you have lots of glass on the outside of the building, in arenas, which need to be blacked out for many of the shows, they tend not to have these lightweight, transparent roofs. They'll have a conventional metal deck roof with insulation and a rubber roofing layer, EDPM or something like that roofing layer over it, and not all that massive. And so what you'll do, and I'd like Joe to, as I said earlier, jump into the Barclays example here, which is a pretty extreme example, but the roof tends to be a leaky point, a weak point. And so you basically make the roof more massive. You use all the standard noise transmission techniques of space and mass and everything else to make that work. Once again, it's a large area and budgets start becoming a concern.

Also with the outside of the building, which typically have lots of glass, how does sound that's inside the seating bowl escape out into the concourses, and then out through the glazing might be there for the building across the street? And so we start talking about how do we make the seating bowl a more sealed up environment than just having, there's a lot of arenas that have completely open concourses. And for concerts they might use thin masking curtains just as a light block and stuff like that. So… do we make more substantial curtains, where we just don't have an open concourse but we have traditional vomitories into the bowl? Do we start talking about doors and vestibules, like a theater or a concert hall, for noise control rather than just a standard masking curtain? So there's things that you have to do and you have to look at every single leak point in the building to deal with that. And at some point, as Gary pointed out earlier, sometimes the site is just inappropriate. And there are buildings that have, just like the outdoor theaters, they have noise level limits inside based on what the noise ordinance is that they're trying to achieve at the nearest sensitive properties. And Joe, I'm going turn it back to you because the Barclays one and the high rise next to it and what you guys did with the roof is a pretty extreme example.

Joe Solway (42:46)

Sure, so the Barclays Centre opened with a lightweight roof on top of it and the developer had chosen not to choose a more massive roof construction. As part of that arena development, they were developing a whole series of residential towers that are going right up to, adjacent to the arena.

Jack Wrightsonl (43:11)

And they were high rise and had direct line of sight view to the roof, which is a little bit in common.

Joe Solway (43:14)

Direct line of sight.

Jack Wrightsonl (43:16)

Which is a little bit uncommon.

Joe Solway (43:18)

So you had a lot of low frequency energy in the bowl coming straight through a lightweight roof, and then you had residential properties very close to that roof. So after it opened, the Barclay Center were looking for how to mitigate that sound. Now, the challenge with a constructed arena is that you don't have the structure, you can't go in and suddenly add a load of concrete if the structure doesn't have the capacity for it, right? And so obviously the structure was designed for this lightweight roof and not for a big, thick concrete layer. So when we're controlling sound out of a space, then we have two means of doing it, either a more massive layer or multiple layers with air spaces in between them. So because the more massive option was not a possibility for Barclays, then we worked with them to develop a green roof, essentially layers of sedum trays of grass that created this structure 10 feet above the original roof. And we found these trays of grass sedum were an effective damped layer. So they had a sort of a similar level of mass to say several layers of gypsum or DensDeck or what we typically do in a sort of a roof deck. But the soil and the plants and the water that construct of these trays are actually very damped. So in terms of their efficiency to radiate sound, it was very low, which was excellent for creating a good damped outlet. And the original master plan for the Barclays Center outlined a green roof on top of it. So we were basically going back to the original masterplan concept for the arena, but then creating this secondary roof system skin on top, that sort spoke to the original masterplan, but then effectively helped to dampen the sound to create an acceptable level in the residences that are right next door.

ASA Publications (45:08)

Must have been nice for them to look at too, to be like, hey, yeah.

Joe Solway (45:10)

Yeah, and then suddenly, now in addition to reducing the sound level, now you're looking at, effectively, a green meadow with wildflowers, bees buzzing, and birds flitting over it. So you've got now effectively a nice meadow view out of your Brooklyn apartment.

ASA Publications (45:25)

Yeah.

Joe Solway (45:29)

So, but you know, it speaks to the old saying that an ounce of prevention is worth a pound of cure. 

ASA Publications (45:36)

Yeah, right.

Joe Solway (45:38)

That if we can get in at the beginning of these projects and help clients and design teams understand the potential risks around acoustics and sound isolation and the potential impact to these communities that surround these venues, then we can more effectively and for less money, less cost to the client, find solutions that will help mitigate it. The later these solutions are addressed in the design, or if they're complete not addressed in the design and have to be addressed after completion, then the cost to effectively mitigate it just goes up exponentially. So the earlier this can be dealt with, the better. So it sort of  behooves us as designers to make sure that we're effectively communicating that to clients and finding ways to convince them, not always possible, but you know trying to convince them of the seriousness of these acoustic implications if they're not locked up.

ASA Publications (46:31)

Yeah, yeah, yeah, fair enough. So it sounds like you've already somewhat answered this, but do indoor stadiums and arenas solve this problem of noise in the community at all?

Jack Wrightson (46:43)

They do, but it's limited. And what's it limited by? It's limited by physics, but it's also limited more primarily about the nature of the building and what it's supposed to do and how it's constructed and all that stuff and budgets. So there are some things, and when we talk about land use planning and things like that, there are certain uses that aren't all that compatible. And what we're trying to do is make them more compatible. And local regulations, the willingness or not of the local authorities to change regulations, which happens on occasion, to allow the facility to be where it is, either by changing the noise ordinances or by special use permits or conditional use permits and things like that. There's a land use planning aspect of it. But there's also the nuts and bolts architectural and acoustical elements of it, is that Joe was just talking about, how do we basically beef up these buildings to allow less sound to escape? And there's, you know, it's a balancing act for the developers of the building, just like everything else. How much money do they spend on any given aspect of it? And at some point, the cost may be too high, depending on the local regulations, that another site is the best option. But yes, are things we can do and there is mitigation that happens, and generally it's made to work out pretty well.

Gary Siebein (48:05)

One of the things that helps a lot is actually, you know, over the, in recent time, the development of algorithms and research that's been conducted and translated into computer software that allows both the study of transmission loss through multi-layer the way you were talking about, Joe, for, you know, once you put all these layers in, that it becomes a pretty complex sound transmission issue, and as well as the propagation of sounds off-site. These programs are pretty well developed at this point and I think help a lot in terms of being able to really examine this from a technical point of view.

ASA Publications (48:43)

So how do you predict designing for large venue acoustics will change in the future?

Jack Wrightson (48:47)

What we're seeing is we're starting to work on more and more 10 to 20,000 seat non-sports facilities that are dedicated for concerts. And once again, this is very market dependent. You can't put one of these in every town across the world. It's got to be someplace that you can do enough concerts of this type that it's worth building a venue, economically worth building a venue of that size, that basically has one tenant, which is touring concerts. And so, you know, you think about a market like Las Vegas, which has far more arenas per capita than anyplace else in the US. And then you add the large performance venues on top of that. It’s got a lot of that stuff, and that’s one of the places where you could conceivably build some of this. And there’s other places around the where we've worked on things like this. But when you do, as noted earlier, when you do a concert-specific building, acoustics are much more important to the developer. They're much more important to the performer. It's not like, yeah, I went into a hockey arena and I played a show there and it's a hockey arena. It's more like I went into this big venue and it sounded really nice. And so that's what you're going for. And so, from a developer standpoint, an architectural standpoint, all the things you don't have to do to make it a sports venue-- I don't have to have all the equipment to do hockey ice. I don't have to spend millions of dollars on LED displays and scoreboards. I don't have to spend millions of dollars on player facilities. So they're much more open to doing acoustical treatment, A, because they need it to sound really good for concerts, because you want to make sure that the acts are happy playing there. And secondly, they can defer the funds that they would have spent on some other function in the sports facility into this. So we have no problem getting rid of glass railings in a concert venue. The sight lines are different enough that we don't need the glass to make the sight lines work to either a center stage or an end stage performer location, as opposed to looking at the near goal for basketball or hockey, which is a much more severe sight line. So that's kind of the trend we're seeing in these large things. The other thing over the years is because of the multipurpose use of facilities, it used to be dome stadiums had almost no acoustical treatment. No one wanted to afford it.

I'm just playing football there. The concert business is lucrative enough for these venues. There's enough concerts that will play these buildings. The rental fees, the food and beverage per capita on that is high that everyone shares in, that they're starting to pay more attention to this now. And so they're more open to spending the money because they know that there's going to be some payback on it because they're doing enough concerts and they don't want to have a reputation of being a really lousy sounding place to play. So those are the two biggest things that we've seen in, let's call it, the last 15 years as sort of developments which are making these large venues a little bit more acoustically friendly.

Joe Solway (51:45)

And to touch on what Jack was just saying there,  we've talked in this conversation around the costs around acoustics and developers or clients not wanting to pay any of those costs. But I think if we can equate, you know, ultimately for people that run and own these venues, it's around how much revenue can they get out of this venue. If we can equate the cost of the acoustics to creating a better experience, where more people will want to come to your venue and spend their time and spend their money, then you can rapidly see that the cost of the acoustic treatment create a better experience is going to result in greater revenue of people wanting to come to your venue because they're going to have a better experience ultimately. So tying the acoustic cost to visitor experience, I think, is important.

Gary Siebein (52:30)

Yeah, that's a good point, Joe. And one of the things that's interesting, there's been a lot of research in architectural acoustics relative to perceived sound quality in natural acoustic concert halls and theaters over decades, actually, and how to predict that. There hasn't been nearly as much research on the qualitative perception of sounds and more subtle aspects of the acoustics of large venue amplified experiences, either for performers or guests. There's been a little bit of work on that done in Europe and this becomes actually an interesting potential topic for the future because there is so much of the entertainment industry that is tied up in these venues at this point. How to maintain an intimate performer-audience relationship in venues of this size, besides being able to see blowups of Taylor Swift on a video screen or something. You know, so that it's different than watching it on your big screen TV at home or in your clubhouse or something like that, becomes a pretty essential question so that, you know, there's still this kind of feeling of I need to go to the arena or need to go to the performance venue. It's such a better experience for me. I need more complex audio playback systems and video displays so that I get that kind of immersion in sound as opposed to just frontal sound coming at adequate or at high levels. So that the understanding the sound qualities, when we've gone into some venues where there's been issues with noise ordinances, we’ve worked with the sound operators and actually surprised because can make kind of fine-scale adjustments in their equalization and other sound mixing parameters they don't notice that have big effects on what's actually going out of the facility, for example, and it doesn't affect what's inside the perception that much. And these are all areas that would benefit from maybe some additional research. But I mean, the facilities are here to stay. I mean, whether it's for stadiums for large touring acts, Taylor Swift and whatever to go play in, or whether it's the facilities that Jack is talking about for 10,000 people in smaller communities and towns. And so, you know, people go to enjoy these acts and they really need to continue to grow in sophistication for the architectural and acoustic systems that are used in them.

ASA Publications (54:59)

Do you all have any other closing thoughts?

Gary Siebein (55:02)

Yeah, this is great. Jack and Joe, appreciate all the discussion and insights. It's fantastic. Thank you.

ASA Publications (55:09)

Yeah, I agree. It’s really amazing how much you have to take into consideration when planning acoustics of large venues, not just in terms of sound within the structures, but also how they'll impact the communities, and all of that. I hope our listeners found this as fascinating as I did. Thank you again for taking the time to speak with me today, and have a great day.

Joe Solway (55:27)

Great, thanks. Thank you so much.

Jack Wrightson (55:30)

Good talking to you.

Keely Siebein (55:31)

Yeah, appreciate the conversation.