Divine Acoustics: Sound Absorption in the House of Worship

Couple in house of worship displaying disapproval of sound

Too Loud or Too Soft? Why Sound Absorption Matters in a House of Worship.

Problem: When it comes to having great acoustiImage of a church interior with sound absorption panelscs in a live setting, many Houses of Worship face a major challenge: most were either not designed and built with acoustics in mind or are actually leased warehouse or gym spaces with high, open ceilings, exhibiting significant echo, reverb and poor intelligibility.

Tight budgets and other priorities often prohibit any upgrades to the sound system, and the costs of renovations are generally too great to consider. So, poor acoustics continue and congregants complain.

Solution: Installation of sound absorption panels is increasingly becoming a popular option for Houses of Worship who need to address acoustic problems. By covering between 17% and 25% of the wall space with acoustic panels, a church can see — and hear — significant improvement at a fraction of the cost of major renovations or upgrades to the sound system.

In the following interview with Primacoustic’s James Wright, we discuss this topic further.

Primacoustic: When it comes to acoustics in a house of worship, what is the top challenge that most facilities face?

James: It’s having the sound character of the room even throughout the space, in such as there being no dead spots in the middle, where it’s not super echo-y in certain spots.

Primacoustic: In other words, a greater consistency in sound quality throughout the room, correct?

James: Yes. You’re trying to make the whole sanctuary sound the same throughout, so that sound is projecting to the balconies. The area under the balcony is often one place that’s challenging, and just keeping that reverberation level down is important so that the intelligibility can be maximized as much as possible.

Primacoustic: The balcony is generally one of the most problematic spaces in a House of Worship, right?

James: Yes, both the balcony itself and underneath the balcony because you need to really steer the PA into those sections, or have some sound reinforcement built into those sections that is independent of the main system. So a lot of it depends on the size of the church, but in a larger church you can often have some fluctuations in how it sounds on the floor as opposed to in the balcony or under the balcony.

Church acoustics sound panels

Primacoustic: And what happens with the sound waves once it gets under the balcony to cause those kinds of problems?

James: Generally, I find that in under the balcony situations, you lose a lot of definition, you lose a lot of high frequencies. So having sound reinforcement there as well as some kind of acoustic absorption to really tune that space and really keep the frequency response nice and even is important. In an under the balcony situation, you’re now dealing with a completely different ceiling height versus the rest of the room, so all the frequency response and reverb times are \different from what the main part of the sanctuary is. So you’ve got to almost look at the under the balcony area as its own individual section.

Primacoustic: What type of acoustic panel approach do you take in an under the balcony environment?

James: It really depends on what’s going on there, what you have for wall space. In most cases, if I can go a 60/40 split between walls and ceilings, that’s going to work really, really well.

A lot of it’s going to depend on what kind of seating is in there, if it’s padded seats, if it’s pews, if it’s hard seats, or kind of flooring materials there. Is it carpet tile and concrete? Is it a some kind of easy-clean linoleum kind of thing? All those things get taken into consideration. The harder the surface on the floor is, the more I’m going to lean on ceiling treatment to get rid of that slap echo that’s going back and forth between the floor and the ceiling.

Primacoustic: What’s really the first step you look at in addressing poor acoustics in a house of worship, sort of from a comprehensive standpoint?

James: First, I start by looking at what the reverb time is, whether I’m physically in the room or whether I’m doing calculations based on room size and materials that the sanctuary is built from. Second thing I look at is what the style of worship is. I’m going to treat the church much, much differently if it’s a rock band up on stage than if it’s an organ and choir type of situation.

Primacoustic: Why the difference in approaches?

James: Because the reverberation is an integral part of that sound. You don’t want to take the reverberation sound characteristic out of the overall sound. A choir singing in a dead room is not as inviting a sound as that lush, organic, rich sound that we’ve always come to come to know of as a church choir.

Primacoustic: Anything else you consider?

James: Those are the first two things that I look at. I’m also very interested in what the building materials are. What is the flooring materials? Are they sitting on pews? Are they sitting in padded chairs? What style of worship? What is the sound system going to be? How is it aimed? A lot of those things will come into play. And what’s the overall goal of the acoustic environment? Is there a lot of multimedia? Are we doing a lot more spoken word? An outline of what the structure of the service is can be very helpful.

Primacoustic: How does the mix of media such as spoken word, music, theater impact how and what type of acoustic panels a house of worship should consider?

James: 90% of what we use in a house of worship situation is a two-inch thick panel. It’s the most even over the entire frequency spectrum, so it’s going to keep the sound as natural as it possibly can.

Primacoustic: Does the two-inch panel also address acoustic issues at the low end?

James: I don’t find you have a lot of bottom end, low end issues in a church to speak of that can’t be controlled by a two-inch panel. Very rarely do we need to use bass traps or a three-inch panel.

Primacoustic: What’s the first thing you do when considering the level of sound absorption needed in a House of Worship?

James: I look first at placement, seeing where those first reflections are occurring with the way the sound system is going to be hung or placed. If it’s a portable sound system, it’s important to make sure it’s going to stay in the same place week to week.

Image of church interior showing acoustic panels

Primacoustic: What about churches that share space with other operations during the week?

James: A lot of what we recommend depends on what’s happening with that exact worship facility, because it could be a thing where it’s being used as a gym in the week and it’s being used as a church on Sundays, that kind of thing. A lot of that is going on, so you really got to be a little bit flexible, really look at what speakers are going in there, how it’s laid out, where our first point of contact is, first reflection point is, and then designing an acoustic system from there.

Primacoustic: And you mentioned reverb earlier, so talk a little bit about maybe what reverb is from a high level standpoint and the difference between that and echo.

James: They’re related, but they’re not the same thing. So reverb or reverberation is a long-lasting echo, for lack of a better term. Such as a long lasting echo of more than 0.8, 0.9 of a second. And the way we measure reverb is a thing called RT60, and that’s the amount of time it takes for a sound to decay by 60 decibels. That’s how much dwell there is in the room, how long that sound lingers in the space.

Primacoustic: What’s the benchmark for acoustic panel design and recommendation in a House of Worship?

James: Our goal is between 0.8 and 1.2 seconds for a really articulate sound in a large space. We want to keep the room sounding large, with some ambiance in the room because you don’t want to walk in and have it feel like your eyes and your ears are in two different rooms. The analogy I often use with people is when you walk across the threshold in a commercial movie theater, your ears and your eyes are telling you different things. You cross that threshold and you hear you’re in a different place.

Primacoustic: Is this different than what you want to expect in a House of Worship?

James: Yes, the design in a movie theater is done for very controlled reasons and that’s an overly-absorptive space for a church. You wouldn’t want to have that much absorption in the space. You want to still have some life in the room. And that’s probably down around half a second of RT60 time is what a commercial theater is going for, so it’s getting more into that studio realm, very, very controlled because everything’s driven from those speakers. You want to hear things coming from the speakers they’re intended to come from the soundtrack point of view and from the effects point of view, so you don’t want to have any interference from room anomalies.

Primacoustic: So, let’s segue back to the example of sound for a House of Worship environment/

James: Right, so going back to the house of worship, we want to keep it between that 0.8 and that 1.2 second place, and we want to have it evenly attenuated over the whole frequency spectrum. So if you just take care of the top end frequencies using say a one-inch panel or something more dense than what we use, what you get is a lack of intelligibility, a lack of top end, a lack of excitement in the sound.

Primacoustic: How does that differ when considering bass treatment?

James: If you go with an overly bass heavy treatment, you end up getting a very thin sound out of the PA and you’ve got to now boost that back up with EQ or with volume and then you run into a bunch of other situations that get you back at ground zero. And so we’ve found the evenness of the two-inch panel really is the most effective in that situation.

Primacoustic: Let’s circle back to echo and what it is.

James: Echo is generally shorter times and you’re going to hear a repeat of it, so if you hear it slapping back and forth, that’s more of an echo situation. Same treatment, but it’s going to be in a smaller room. You’re going to have that in rooms of say 30, 40 feet at their longest measurements kind of thing.

Primacoustic: So echo is more noticeable in a small room?

James: Yes, echo is more noticeable in a small room, and reverb is more noticeable in a large room, just because the distance the sound wave is traveling … It’s all about the sound of the reflection bouncing back and forth. If you’ve got a 30 or 40-foot long room, it’s going to travel back and forth at a much quicker rate than in say 130-foot length. It’s going to have more time to develop, and you’re not going to hear that slap back, that defined slap of it. You’re going to hear more of a dwell in the room and it taking that time for the sound to attenuate.

Primacoustic: Let’s talk a second about glass. Many houses of worships have lots of glass or stained glass, so how does glass impact the sound and what are the best approaches to addressing sound issues caused by glass?

James: Everything that any building is made of has an absorptive or reflective property, and we use a data point called NRC to measure that, which goes from zero to one on the scale. Glass would be at the 0.05 of that scale, so highly reflective and almost non-absorptive whatsoever. A lot of times with glass there’s not much you can do other than put something on a wall facing it to try and trap that reflection as quickly as you possibly can.

Primacoustic: But even with lots of glass, the basic formula of 17% to 25% coverage still applies?

James: Yes, the number one step in creating a better acoustic environment in a House of Worship is getting the correct amount of absorption for the size of the space. For this reason, the calculation we generally use is anywhere between 17% and 25% of the wall surface area, and that is generally enough to absorb that ambience out of the room. We’re much more concerned with the ambient sound than the direct reflection in most cases, so a lot of times it comes down to a balance between aesthetics and acoustics, and with most Houses of Worship, it’s going to be aesthetics winning.

Primacoustic: And this points to the importance of having an acoustic plan in place as early as possible, correct?

James: Yes. One of the main reasons it’s great to get an acoustic plan going in the design phase of the building is so that you can do things like not have parallel walls, not have glass surfaces parallel to one another. This level of planning helps eliminate the possibility of there being time for echoes and reverberations to propagate. A lot of the preventative measures can be done in the design phase and in the pre-build phase and the build phase much more cost-effectively than it can be in an aftermarket kind of situation.

Primacoustic: Let’s talk a little bit about ceilings. There’s so many houses of worship that have very high ceilings, and in these cases, can acoustic clouds still be effective in these high ceilings?

James: Yes, definitely. Whether a high or low ceiling, that still affects the amount of time it takes sound to bounce back to you, and that’s going to increase your reverberation time. We want to try and bring that down as much as possible. So ceiling clouds, and/or a combination of ceiling clouds and baffles work great for addressing this.

Primacoustic: What’s the general rule in hanging ceiling clouds versus baffles?

James: Clouds are generally hung face to the floor, whereas a baffle is hung vertically, and they’re going to be trapping reflections from different angles. In wide churches or long churches I like to use a combination of the two because, again, you’re trapping those reflections for as many angles as possible and not allowing them to reflect off other surfaces. Getting the ceiling clouds up and out of sight is a very effective tool for churches to use because a lot of times they don’t want to see the panels, and hiding the panels in the ceiling supports that balance between aesthetics and acoustics.

Primacoustic: One criticism of post-construction solutions like retrofitting panels to a church or house of worship is that they often look like out of place, like an afterthought. Talk about the Paintables line of panels and how Paintables can really help address that aesthetic appeal.

James: The Primacoustic Paintables line was introduced just for that purpose. You can literally paint the panels the same colors as the walls of the church. Now, painting them is a little more than a simple DIY project, but anybody with any experience in using a paint sprayer can do this.

Primacoustic: What type of paint is best?

James: Any type of paint, as long as it’s no glossier than an eggshell, will work really, really well. Just a light latex paint just sprayed on will work great. As light a coating as you can get is the most effective.

Primacoustic: Does the paint affect the sound absorption characteristics of the panels?

James: There’s virtually no difference between the acoustic performance of the fabric wrapped and the painted panels if they’re painted using two or three light sprayings of paint on there. Where you start to run into problems is when you use a high gloss paint where you need to add six or eight coats of paint to cover that. So choosing accent colors, or choosing a wall color that is relatively light is the best way to get as little paint on there as possible.

Primacoustic: And the Primacoustic Paintables are not just for painting, correct?

James: Right. The same panels can be printed on, so any image that you can think of could be printed directly to the face of the panel without affecting the acoustic properties of the panels. By the way, a lot of people leave the panels white too, especially in older churches. They find the white color blends in the best with the décor of the church.

Primacoustic: What’s the first step you take when a church approaches you about installing acoustic panels?

James: We start off first with a budget. This relates to how much you’re going to need to get into the space to make it acoustically effective. Where the panels go, where they’re hung is really a minor consideration. It maybe adds 10% to 15% to the budget if we start looking at more ceiling panels, that kind of thing.

Primacoustic: So getting a sense of the scope of the work is essential in the first stage.

James: Yes. We want to start with getting that base number. And then we start really tweaking on the design based on the budget parameters to make it as seamless and as invisible as possible. I’ve seen some awfully creative ways of adding panels that people have done over the years and it really, it can be quite an enhancement to the facility. A lot of the creativity part of it comes from the congregants themselves or the committee as to what they’re willing to give up aesthetically to make the room work acoustically.

Primacoustic: In recent years, the advent of more powerful PA systems and concert-style Christian music has really introduced a new set of acoustical problems. To achieve the feel of a rock concert, sound pressure levels are increased to the point where the room’s ability to dissipate sound energy is really sort of completely lost. So how can acoustic panels really help fix a room that’s too loud and has pressure sound levels?

James: So there’s two approaches to addressing that. First one is, you’re not fighting against the room sound anymore. The PA is able to do its job and just focus on getting sound out into the congregation, so it’s a much more focused sound. You’re not trying to get over sonic anomalies. Let’s say you have a hot spot at 160 or 140, something like that. Well, the acoustic panel is going to help minimize those hotspots, minimize those hot frequencies, bring everything down, attenuate it to an even level. In this case, the room is much more controlled and much more precise as to what the sound person is hearing. So although it’s actually quieter, it gives the perception of being more focused and tighter and louder. The sound person has much, much more control. The room doesn’t control the system, the system controls the room, and that’s much more what we’re after.

Primacoustic: What about the stage area in these type of environments?

James: One of the other things I often do in a house of worship where there’s a worship band is I will treat the stage area very, very heavily. A lot of churches have gone to using the plexiglass cage around the drums, which is fantastic for direct sound, but what the unintended consequence is the drum sound hits the front of that plexiglass, hits the wall in behind it, and that wall now acts like a giant resonator. Although the sound of the symbols and maybe the snare drum, the higher frequencies, are attenuated by it, the actual sound of the drum kit is as loud or louder than it was without the plexiglass screen.

Primacoustic: What do you do in this situation?

James: The secret there is to have acoustic treatment behind that plexiglass screen as well, so on the back wall that the drummer’s playing from, and that’s going to take care of those reflections coming off the plexiglass. All of a sudden the drums sit better in the mix. Same thing with stage monitors. The singer’s voice is now hitting that back wall, again, the wall’s acting like a giant resonator, uncontrolled volume for the sound man. Open back guitar cabinets pose the exact same problem.

Primacoustic: So sound absorption is not just about sound in the main room, it also plays an important role on the stage as well.

James: Yes, that is correct. If not treated, all these areas work in unison to create a real problem for the front of house person, who is oftentimes a volunteer and not a professional. And often the worship band is semi-pro at best, and they haven’t learned how to get their sound at a low volume. So it’s something that the sound team has to work with and get that stage as dead as possible. And as a result, the sound can be mixed through the PA and it’s not too loud, too. So it’s really helpful to get that stage sound under control and get the musicians playing as quietly as possible, while getting the actual stage acoustics as dead as possible.