When it comes to church sound, much of the focus in recent years has been on sound systems, and more specifically on how those systems’ coverage patterns can keep sound on seats and away from reflective surfaces. Technological advances like beam steering and columnar arrays have significantly improved the sound inside sanctuaries and other areas of houses of worship. But the attention that these solutions have received, as deserved as it is, can cause those concerned with the quality of church sound to overlook two other domains that are just as critical to quality audio, if not more so.
“There are three primary areas that concern sound in a space and the electro-acoustical one—the sound system—is one of them, but the other ones don’t get the attention they should...”
—DENNIS Paoletti, Principal, Paoletti Consulting.
Acoustics and noise control are distinct areas of concern for house of worship (HOW) sound, and form two important sides of what ought to be a tripartite approach to sanctuary sound. “There are three primary areas that concern sound in a space and the electro-acoustical one—the sound system—is one of them, but the other ones don’t get the attention they should,” observes Dennis Paoletti, principal at Paoletti Consulting, a Bay Area acoustical consultancy that has many churches in its portfolio. “What we’re looking at are the acoustical properties of the space itself—the room acoustics—as well as the sound isolation, and noise and vibration control. And we’ll look at those in the context of the plan of the church; the type of structure it is—a cathedral, a former shopping center—all affects how and what type of acoustical and noise issues it can encounter.”
Distinctions
Cameron Girard, an acoustical technician at Acoustics First, a consultancy in Richmond, Va., delineates acoustics and noise control as two sides of the same coin but with a critical difference. “Acoustics is about optimizing a space for sound quality and specific goals such as speech intelligibility and music performances,” he explains. “Noise control, on the other hand, is about minimizing the sounds you don’t want to hear in a space, such as the noise generated by HVAC and other mechanical systems.”Acoustical analysis of spaces involves vetting a number of key and universally recognized criteria. “We’d look at things such as the reverb time of the room and the quality of reflections from the stage,” Girard says. “It would also be important to analyze the quality of the reverb itself; for instance, spaces used for acoustical instruments or that rely on choral music tend to have longer reverb times in the bass frequencies,” at or below 250 Hz for males.When looking at noise control issues, the range of possible problem areas can be considerably wider, anything from mechanical systems like HVAC and plumbing to noise from adjacent areas such as cry rooms and classrooms to external noise from traffic. Structural vibrations can be especially vexing to track down and isolate, and that’s where acoustical expects will often interact with architects and mechanical engineers.
Once identified—and that requires both measurements of the space and an experienced ear—acoustical problems are largely remedied using absorptive solutions: fabric, foam and fiberglass products, more and more of which are available off the retail shelf but which also have a wide array of bespoke solutions available, that deaden the space and stop or largely attenuate reflections.
Absorptive solutions can be placed in a wide range of locations, anywhere from the ceiling to the backs of chairs and pews using upholstery. “You want to stop slap and flutter echoes with absorption, or use diffusion and diffraction to break up sound waves,” Girard says. Location and choice of absorptive materials is an aesthetic decision as much as an acoustical one, and consultants will work with architects and interior designers to make sure that these treatments blend in as much as possible with a church’s décor. Another key point in this process is to avoid attenuating reflections so much that a space loses its liveliness. “That has to be considered in conjunction with the worship style a church uses,” says Girard. “Too little reverberation and it deadens music; too much and it affects speech intelligibility.”
Air Conditions
HVAC systems have been chronic causes of noise problems for churches for decades, because houses of worship usually have to fill a sizable amount of cubic feet with a lot of cooled or heated air, and it often has to flow continuously. As a result, HVAC noise runs the gamut from the noisy movement of air through ducting to the vibration caused by compressors starting, stopping and running. Paoletti notes the differences between an architect’s perspective on this and that of an audio professional. “The architect will want the shortest distance between the mechanical systems and the sanctuary, for cost reasons, while an acoustical consultant will advocate for the opposite, to minimize the potential for mechanical noise interfering with the sound in the sanctuary,” he explains.However, distancing HVAC components such as compressors and fans from the sound-intensive areas of a building, such as a sanctuary, classroom or rehearsal space, brings its own issues. The longer ducting needed to transport air to the space increases the potential for air-handling noise. That can be addressed using ducting lined with sound-deadening material. As a rule of thumb, Paoletti estimates that air noise can be reduced by about 1 dB per 10 feet of ducting, but that will also be affected by the type and thickness of the deadening material, and by the geometry of the duct itself, which will in turn be determined to some extent by the architectural and structural nature of the space that it has to traverse. Rectangular ducting tends to be the most efficient in terms of the balance between air transport and noise reduction, but once inside the sanctuary an architect may call for circular ducting, which is made from bendable fiberglass and metal foil that offers a high degree of flexibility and thus has aesthetic advantages. However, that type of ducting is less rigid than rectangular ducting, which is made from sheet metal. Circular ducting can leak, releasing noise in to the environment, and it can wobble as a result of air pressure, inducing low-frequency noise. What seems like a cat-and-mouse game underscores the complexity of HVAC noise in sound-critical environments and the importance of architects, mechanical engineers and acoustical consultants working together as early in a design process as possible.
The Big City
Churches—and everyone else, it seems—are moving back into urban cores, often taking over repurposed buildings that weren’t initially designed as houses of worship. And in this increasingly dense environment, churches (and everyone else) are experiencing an entirely new generation of low-frequency noise.
In addition to bass-intensive music and sound-reproduction systems, cities are under assault from truck and car engines tuned for maximum SPL at frequencies that once were limited to NASCAR tracks. Steve Haas, principal at SH Acoustics in Milford, Conn., and Los Angeles, recalls how Calvary Christian Church in Pacific Palisades, Calif., watched the city grow up around it since it was built in 2000, including the proliferation of low-frequency street noise from vehicles accelerating up the adjacent steep road. Haas was called in to deal with this and other acoustic issues a couple of years ago. “At times, you might as well have been out on the street, it was that loud,” he remembers.Haas took measurements of the SPL and the resulting Noise Criterion (NC) scales. The latter is used for rating indoor noise and consists of a set of criteria curves from 63 Hz to 8 kHz. An NC level is a standard that describes the relative loudness of a space, documenting the extent to which noise interferes with speech intelligibility. The church’s NC values exceeded 40 at times, which qualifies as exceedingly noisy for a worship space. The structure’s wrap-around windows let in lots of light but also plenty of low-frequency street noise, as well. Part of the recommended solution was to add interior window sashes—essentially indoor storm windows—that added glass sound barriers, but more importantly, created a two-inch air gap to isolate the interior from the external noise. In addition, two kinds of glass are used: laminated for one pane and tempered for the other, to avoid creating resonance between two like materials. “Standard thermal panes alone won’t do much about keeping out low-frequency noise, but an air gap between them makes a huge difference,” says Haas. Not all churches can avail themselves of the remedy described above because of the emotional importance of stained glass windows, which many congregations don’t want to see dimmed by additional glass. And be advised that the worst low-frequency noise often falls below the 63-Hz bottom of the NC scale. “You ideally want to achieve 20 to 25 on the NC scale for a worship space that has strong recording and broadcast requirements, but the reality in remedying existing issues like this is you’re going to get closer to 30,” says Haas. “The goal is make the [noise] situation better. You rarely get perfect.”
Acceptance
John Storyk, principal in upstate N.Y.-based Walters-Story Design Group and registered architect and acoustician, agrees that perfection isn’t achievable most of the time, for noise control or acoustics. He’s turned to modified versions of the room-in-room construction techniques he’s used for years on world-class recording studios, where noise intrusion is sometimes an existential problem. For instance, instead of floating rooms on springs and other devices to isolate them from sources of vibrations, he’ll apply modified versions of that to the larger scale of houses of worship with the same intent: decouple the critical spaces physically from the world around them by cutting through the edges of room floors and connecting them instead with flexible, non-vibration-conducting caulk.But in some cases, like Crossroads Church in the Bronx, N.Y., which is a few blocks from a subway line whose rumblings can be heard on occasion during quieter sermon moments, or a church in Belo Horizonte, Brazil, which is on the departure path of a local airport, you just acknowledge that here is only so much noise you can control.“Acoustics and noise control are part of the same proposition,” he says. “We can do some amazing things when it comes to reducing noise intrusion and making sanctuaries better for speech and music. But at the end of the day, we know we have limits, in terms of physics and in terms of budgets. After that, you have to have faith."
