TO THE UNINITIATED, THE REALM OF ACOUSTICS SEEMS TO BORDER ON THE OCCULT. AFTER ALL, HERE WE ARE DEALING WITH COMPLEX, SUBTLE AND INVISIBLE FORCES—MYSTERIOUS INFLUENCES THAT SOMETIMES INTERFERE WITH THE PREACHING OF THE WORD AND FRUSTRATE THE MAKING OF JOYFUL NOISES UNTO THE LORD.
As a consequence, acoustical problems in churches are often misdiagnosed as inadequate sound systems, poor musicianship, or just having the PA either too loud or not loud enough. But when people complain that they can't understand the sermon, or that the praise band sounds like mush, you're likely dealing with—at least in large part—acoustical problems.
For clear insight into this arcane subject, I queried five experts on church acoustics. The wealth of information they provide will give you a head start on recognizing and fixing acoustical problems. Not surprisingly, as great minds often think alike, many responses were nearly identical. So those who are quoted—except as noted—are usually speaking for the group.
HOW DO YOU KNOW IF YOU HAVE A PROBLEM?
You can start by clapping your hands and looking around. “Simply clap your hands loudly and count how long it takes for the sound to disappear,” says Peter Janis, president of British Columbia, Canada-based Primacoustic. “If it is longer than ‘one Mississippi', you will likely have intelligibility problems.”
Poor intelligibility means that people can't understand the sermon, or lyrics of songs, for that matter. “If you look at the walls, ceiling and floor, “ Janis continues, “and all the surfaces are hard—gypsum wallboard, glass, concrete or hardwood—then you can be certain you will have a long reverberant tail.”
You also need to pay attention to complaints. “If members of the congregation can't understand the worship leader, then speech intelligibility is the issue,” says Jeff Lantz, general manager of Auralex Acoustics in Indianapolis. “If members of the worship band can't hear each other, and are having feedback issues, then stage volume and resonance are the culprits.”
Chuck Walthall, founder of Walthall and Associates in Pensacola, Fla., puts the whole question in a nutshell: “A telltale sign is when the third new loudspeaker system still doesn't fix the problem.”
NAMING THE BEAST
Before you can tame the acoustical beast, you need to know exactly what you're dealing with. “The most common acoustical problems faced by a church are excessive reverberation and late-arriving reflections that are perceived as an echo,” explains Vance Breshears, director of the San Diego office of Acoustic Dimensions. “Reverberation, which is defined as a diffuse sound energy, can be a problem when it's too strong or excessively long. Likewise, a late discrete reflection sounds like an echo and impairs clarity.”
Lantz echoes (sorry) Breshears' comments, with added detail. “A slapback echo typically occurs when you have a large flat or inward curved surface—like a balcony front—that returns to the stage area with a very distracting effect,” he says. “Flutter echoes are caused by parallel reflective surfaces, typically side walls, that produce a clicking, ringing or hissing sound when you clap your hands. Both can be solved with proper acoustical treatments.”
WEIGHING THE SOLUTIONS
So, now that you know you have a problem, and you basically understand it, but how do you fix it? First, you need to marshal available resources.
To start, make sure you understand the lingo. If you don't clearly understand the difference between reverberation and echo, study the glossary in the sidebar. After that, school yourself with information from the library, bookstores and websites.
Manufacturers of acoustical treatments have ample information available on their sites; some include step-by-step guides for calculating what materials you need and where to put them. But be careful, as it can get complicated. “Manufacturer's published data will show the absorption for their products,” says Nick Colleran, vice president of Acoustics First Corp. in Richmond, Va., “but there are certain caveats such as allowing for whatever materials are already on the walls. You will need less covering on a wall that is already partially absorptive as opposed to a hard wall.”
Once you've completed “Acoustics 101,” you're at a fork in the road. Is this a job you can tackle as a DIY project, or do you need to call in a professional? “A DIY project is risky only if you do not diagnose the acoustical problems first and develop a plan with regard to what materials will tackle specific problems,” says Lantz. Breshears generally agrees, although he adds a note of caution:
INVALUABLE ADVICE
As a rule of thumb, if the room has relatively simple architecture and you simply want to deaden it by adding absorption, and you don't need to balance amplified music with choirs or congregational singing (more on this later), the more likely you can do an acceptable job yourself.
“In many ways, you can think of acoustics in the same terms as installing a PA system,” notes Janis. “Pretty much any musician can put up speaker and plug in a mic. The same applies to acoustics. Go into a gymnasium and put up panels on the wall, and at one point the room will change. A simple rule of thumb is 20% to 30% of wall coverage using quality acoustic panels. But, just like with loudspeakers, better positioning will give better results. The same applies to hiring an acoustician. The professional will elevate the room's performance from perhaps 80% to 95%, which can be critical when the room has to perform multi-functional roles.”
A BASIC EXAMPLE
Let's assume for the moment that you're trying to take a small “gymnatorium” and make it work better for high-dB youth worship. How do you go about it?
“High-energy spaces are common DIY projects where you simply want broadband dampening,” states Walthall. “The idea is to take the room acoustics largely out of the equation.”
Colleran has some specific tips. “Excess reverberation is controlled by acoustical wall panels, whereas low-frequency control requires bass trapping which can be achieved by barrel-shaped devices that also serve as mid-range diffusers,” he says. “Flutter and slap-back echoes can be controlled by scattering devices without introducing excess absorption. This will control the problem and give clarity, while still retaining some ‘life' and ‘warmth' in the room.”
And what do you use to damp-down your room? “The most common acoustical panel for church installation is a fabric-covered, glass-wool panel,” says Janis. “These come in various sizes, shapes and densities. Smaller panels grouped together are a lot easier to handle than the larger ones, which can require a lift truck to put in place, so these are a better choice for a DIY installation.”
Of course, you could make your own panels, but several experts warn against this approach. First, absent expensive manufacturing techniques, your panels could come apart from handling and vibration. Second, and more importantly, materials from reputable manufacturers will meet all fire standards, where your DIY panels could get nixed by the local fire marshal.
You also need to make sure that your materials are effective in the frequency range where problems exist. For voice intelligibility, that's the frequency range from 300 Hz to 2,000 Hz, with a mid bump around 500 Hz. “You need to ensure that the panels you put up work in the intended region,” Janis adds. “For instance, there's no point in putting up a low-density acoustic foam if it only absorbs sound above 500 Hz.”
THE BOTTOM LINE?
If still undeterred, how much should you budget for a DIY fix? “An estimate for the cost of simple treatments can be made by determining the Sabins of absorption required,” says Colleran, “and calculating the number and type of panels needed from the manufacturer's test specifications. For large quantities, it helps to call for a quote that includes delivery and any needed hardware options.”
Breshears adds: “For problems that simply need sound absorption, we often recommend fabric-wrapped fiberglass or mineral wool panels. These usually run about $8 to $12 per square foot, not including shipping or installation.”
CALLING FOR HELP
Now, let's assume your room is quite large, or it has complex architecture, or you have to balance worship elements with differing acoustical requirements—spoken word, drama, amplified music, choral music and/or congregational singing. Maybe all of the above. You need professional help. How do you find it?
“The National Council of Acoustical Consultants is a good reference,” according to Lantz. “Also, if you visit another church that sounds fantastic, it's likely an acoustical consultant was involved. Find out who it was.”
Janis states that “a number of sound contractors that are experienced with acoustics can prove to be helpful,” and adds that, “the Acoustical Society of America is a good resource.” However, on a cautionary note, Breshears leans toward referrals rather than trade group memberships. “Associations or certifications don't necessarily ensure that someone really knows what they are doing,” he contends. “A proven track record and a good referral from a trusted source is your best bet.”
TACKLING SPECIFIC PROBLEMS
Here are some tips for attacking specific problems, compiled and condensed from all our experts.
Improve Spoken Word
Intelligibility: Try to get reverberation time under one second. Acoustical panels about 2-inches thick usually do the job, but don't overdo it. A dead room, with no early reflections, makes speech sound dull and flat.
Control Amplified Music: Also keep reverb time under one second, perhaps less. Be prepared to do more bass trapping, and watch out for slap-back echoes that will be painfully apparent with percussion. Consider a mix of 2-inch and 3-inch panels, plus diffusers where necessary.
Choral Music and Congregational Singing: Yikes, now we have to go in reverse. If you take too much reverb out, then the choir flattens out and congregational participation diminishes. (Rich, early reflections are why people like to sing in the shower.) To a certain extent, you can add electronic reverb to the choir to “fatten it up,” but the reverb will be coming only out of the PA, not physically from the room. Churches that do both amplified music as well as choral music or congregational singing (or both) are most in need of expert help, as a critical balance must be achieved.
ADVANCED SOLUTIONS
If your auditorium must accommodate both contemporary amplified music and traditional music, either in worship or for special events (e.g., classical orchestral or choral concerts), then it's time to bite the bullet and consider advanced solutions, including variable acoustics.
Up until about 10 years ago, your only viable option was physically changing the space with retractable heavy drapes and—this is enormously expensive—moving walls that open into bass reverberation chambers. Today, you have another option: active (or electronic) acoustical systems. Completely separate from the PA, these employ multiple microphones and at least a couple dozen small loudspeakers (and often small subwoofers as well) along with extremely sophisticated digital processing to generate realistically reverberant acoustical environments. You can't take reverberation out of a room, but you can make a very dead room sound like a Gothic cathedral. “These systems generally sound good and provide great flexibility,” says Breshears. “But the main drawback is cost.” Nevertheless, Walthall sees more of them in the future. “As the technology continues to develop and the price lowers, they will become a vital part of the worship experience.”
LAST WORDS
Though acoustics itself is objective science, the application of acoustics involves subjectivity, as observed by Lantz. “What sounds good to the worship leader may sound awful to the choir director. When you consider that most houses of worship have multiple functions, it presents a difficult task to the acoustical consultant. That said, usually you can strike a balance so that speech intelligibility is improved without sacrificing musical clarity or congregational participation.”
It's a balance often difficult to achieve, but with solid knowledge, the right materials, careful planning, and experienced help, it can be done. No occult rituals required.
MUST-KNOW ACOUSTICAL TERMS
? REVERBERATION - Ambient, diffuse sound energy that “tails off” inside a room. Think “Gothic cathedral.” Long reverberation times are good for organ and choir, bad for speaking and amplified music.
? EARLY REFLECTIONS - Sounds that bounce back from nearby surfaces. These can be helpful for congregational participation. Think “singing in the shower.”
? LATE REFLECTIONS – Discrete echoes that should be avoided. Think “mountain canyon.”
? ABSORBERS - Acoustical materials that absorb sound. Usually they are flat, fabric-covered panels of various thicknesses.
? SABIN – A unit for measuring sound absorption. One metric Sabin equals 100% sound absorption over one square meter.
? DIFFUSORS - Acoustical devices that break up the sound, turning destructive late reflections into diffuse reverberation. They have rounded, irregular, or pointy shapes.
? REFLECTORS - Smooth surfaces, flat or slightly curved, deployed to create desirable early reflections. Reflectors are usually hung from the ceiling.
