Mitigating Unwanted Noise in Fitness Centers

From plyobox jump training and slam ball sessions to group exercise classes set to a pounding bass beat, today's most popular workout environments create a lot of noise.

"There's so much energy in these fitness facilities," says Shawn Saathoff, executive vice president and chief consultant for Acoustiblok Inc., a Tampa, Fla.-based manufacturer of sound-attenuating construction materials. "They have a P.A. system with an instructor giving instructions, and they crank it up. That's the whole idea. It's why people go to fitness facilities. But that's what causes all the problems, because you have amplified, dynamic sound in a facility, and that energy is being forced into the building itself."

"Sound is really a complex science, especially within a fitness facility environment," says Chris Chartrand, director of marketing at SofSURFACES, a rubber-flooring manufacturer in Ontario, Canada. "There are many factors."

Sound travels in two basic ways — through the air and through impact. A building's walls, windows, doors and utility penetrations factor into how freely airborne sound travels from one building space to another, while impact sound is transmitted largely through vibrations in flooring and other connected structural elements. The denser the material, the faster the sound travels.

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"It's multiple things that cause the problems," Saathoff says. "Most people — whether it's a fitness facility owner, the franchise company, the architect, the contractor — focus only on one aspect. They all focus on the demising wall, the wall that separates them from their neighbors. The demising wall is 65 percent of the problem. The rest of it comes from all the building's other tie-ins — the front facade of the building, the back of the building, the roof assembly and the concrete slab. They all serve as a sound transmission path."

The good news about noise is it can be attenuated using certain products now available to fitness facility designers and operators. Here are a few:
 

Isolation membrane
Acoustiblok serves as an isolation membrane within walls and other building components. Specifically formulated to meet fire codes in commercial applications, the malleable material comes in 4½-foot-wide sheets measuring a mere eighth of an inch thick so as not to compromise standard depths of window frames and door jams. Customized screws allow the material to be affixed to metal studs in a countersunk fashion, without the screw heads coming in contact with drywall, thus dampening the resonance of the entire wall assembly.

"Drywall rings like porcelain," Saathoff says. "It gets excited and actually generates sound. When you screw it to a metal stud in a commercial building, the metal stud resonates and the sound goes right to the other side. One side of the wall behaves like a microphone, and the other side behaves like a speaker."

Acoustiblok dampens the metal and drywall it separates at each stud while hanging loose between studs. "It's not rigid like drywall or plywood," Saathoff says. "It's a viscoelastic polymer, so when it's excited with acoustical energy, it vibrates internally and diminishes that energy within its own mass. A lot of the airborne sound that would typically resonate off the back of the drywall in the stud bay is reduced."

The membrane is taped at the seams and sealed around any penetrations in the wall, such as windows and electrical outlets. A wall can be treated on one side of the stud or both. According to Saathoff, one layer elevates the sound-attenuation of a wall from 39 decibels to 53 (a second layer bumps the decibel-attenuation to 57). Loading the stud bay with a 3¼-inch thermal insulation product called QuietFiber enhances the system even further. Its density of four pounds per cubic foot is particularly effective at dampening low-frequency sound such as amplified bass beats.

"The big thing with workout facilities that gets overlooked by the build teams most of the time is that they rely on STC, or Sound Transmission Classification, alone," Saathoff says, referring to the industry rating system applied to airborne sound. "You can't successfully rely on STC alone when you're trying to isolate a fitness facility from a neighboring tenant, because fitness facilities radiate wider dynamics, meaning lower frequency and higher frequency, than what the STC criteria is."

Saathoff explains that an STC test covers a range of 125 to 4,000 hertz, while a workout facility's speaker system is likely to produce a range of 20 to 20,000 hertz. It can prove particularly problematic when a fitness provider sets up shop in a strip mall. "For developers and investment firms to lease to a fitness facility and not take these things into consideration, and then blame the fitness facility, is — to put it bluntly — moronic," Saathoff says. "It's like asking for disaster."

Acoustiblok can be installed in existing facilities, but retrofitting entails ripping out drywall during off hours or, worse, while the business tries to operate. It can also be incorporated with existing two-sided walls when a third layer of drywall is built out in accordance with the business's desired aesthetics. In that scenario, the product is hung behind the new wall as a curtain, or "diaphragmatic absorber," as Saathoff puts it. This combats what's known as the "triple-leaf effect," whereby the middle layer of drywall resonates and energizes both outer walls in opposite directions.

The membrane is applied and functions similarly in ceiling assemblies, particularly if the ceiling is drywall. Drop ceilings, meanwhile, can employ sound-absorbing Acoustiblok ceiling tiles, which can then be backed by loose-laid squares of membrane cut slightly larger than the tiles so as to overlap the drop ceiling's framework grid.

A self-contained fitness facility (one not located in a strip mall) can incorporate Acoustiblok throughout the building, which can get costly, or only in designated areas that produce a lot of noise, according to Saathoff. A third approach is to isolate spaces, such as administrative offices, as quiet escapes.
 

Hollow stanchions are key to duraSOUND’s ability to attenuate sound transfer through a building’s floor. [Photos courtesy of sofSURFACES]

Flooring tile
Rubber flooring is standard treatment for weight rooms where barbells, dumbbells, kettlebells and other heavy workout accessories are likely to be dropped. Moreover, rubber is commonly placed underneath selectorized weight machines and cardio equipment. In all cases, rubber will help dampen some unwanted sound transmitted through flooring to other areas of the building.

That said, rubber flooring manufacturers have invested in research and development to heighten the sound-attenuating performance of their products.

"Where flooring comes into play is impact sound," says sofSURFACE's Chartrand, whose company introduced a product called duraSOUND last year for the sole purpose of mitigating noise more effectively in workout areas. "You take any fitness facility today, they're running high-impact classes, dropping free weights onto the floor. CrossFit people are jumping on and off boxes. You have eight guys doing that, and you're going to get serious audible structure-borne sound transfer from one space to another."

Whereas most rubber fitness flooring is a half-inch to three-quarters of an inch thick, duraSOUND comes with profiles measuring 2 inches or 2¾ inches. The 2-foot-square locking tiles, described by Chartrand as "a fitness tile with more structure and layered mass than a standard fitness tile," can be installed wall to wall or underneath specific pieces of equipment.

Even the company's own standard fitness flooring — 1.25-inch-thick duraTRAIN — doesn't stack up by comparison. While the duraTRAIN tile is raised off the floor slightly by a solid-core stanchion, "the duraSOUND stanchion has a hollow core, so essentially you get more of an air gasket between the surfacing system and the actual concrete surface," Chartrand says.

To see exactly how well the enhanced design works, sofSURFACES commissioned Riverbank Acoustical Laboratories in Geneva, Ill., to test duraSOUND using different weights dropped from different heights. When a 25-pound weight is dropped on the 2-inch-thick variety, the flooring reduces noise by 34.4 decibels from a drop height of 36 inches (compared to a bare 6-inch-thick concrete slab) and by 30.8 decibels from a drop height of 60 inches. When a 55-pound weight was dropped from those same two heights, the 2-inch duraSOUND's noise reduction was 31.6 and 26.6 decibels, respectively.

The thicker 2¾-inch tiles fared even better, with a 39.6-decibel reduction when 25 pounds was dropped from 36 inches, and a 38.4-decibel reduction from 60 inches. The 55-pound drop saw reductions of 40.7 and 35.6, respectively.

"If you have six-inch concrete floors within the building, every time you add layered mass, you're going to help mitigate sound," Chartrand says. "But it's how far you're willing to go to really improve the level of insulation."
 

Eleiko’s SVR Platform is raised off the floor and features layered impact zones designed to mitigate noise associed with dropped weight during Olympic lifts. [Photos courtesy of Eleiko]

Weight platform
Facility operators can go further than flooring. Another layer of sound-reduction takes the form of the modern weight platform.

"We've seen a shift in what people are doing at the gym. Olympic lifting has become incredibly popular," says Rickard Blomberg, who manages the North American operations of Eleiko, a Swedish manufacturer of Olympic bars, plates and platforms. "When people drop weights while they're doing Olympic lifts inside the gym, they annoy other members, because it gets very loud, and obviously you have the problems of the vibration and sound transferred through the building. It's a tricky thing to solve, really. We looked specifically at a weightlifting platform and tried to see what we could do."

Rubber alone in a platform's impact zone is insufficient, Blomberg says. "Rubber might absorb the sound and vibration, but then you have the issue of bounce. Obviously, when you're dropping weights from overhead and they bounce up to chest height, that can be incredibly dangerous. It's not a solution that will work."

The Eleiko SVR Platform measures slightly more than four inches thick and is raised off the floor on corner pedestals. The system's impact zone features four layers: a rubber top layer, a layer of bonded foam and two layers of what the company calls ARP 220. "It basically functions like memory foam in a Tempurpedic mattress," Blomberg says of ARP 220. "It's going to take up that original shock, but when you release it, it's going to come back to its original shape."

Eighteen months in development, the SVR Platform was introduced this March at IHRSA 2017 in Los Angeles. Though testing results quantifying its ability to attenuate noise were not available as of this writing, the product has already been adopted by major fitness franchises, including 24 Hour Fitness, Life Time Fitness, New York Sports Clubs, Equinox and Gold's Gym, according to Blomberg. "They've all had this issue, and there hasn't been a good solution," he says. "With years of knowledge in the weightlifting industry, we said, 'Let's solve this,' and the product we have now is very well received. Functional training and Olympic lifting are such incredibly interesting trends, and we're happy to be part of that."

No one product alone can entirely solve the complicated sound issue. Blomberg most often sees the SVR Platform installed in concert with wall-to-wall rubber flooring. Acoustiblok needs flooring to complement its own effectiveness, according to Saathoff. "The one wall is not the solution," he says. "It's part of it. It's the foundation for the solution, but treating the whole envelope of the studio is the way to do it properly."

"The most appropriate approach to mitigating sound in a fitness facility is to factor both airborne and structure-borne noise," says Chartrand. "You can't have one without the other. Your floor is only going to give you so much, because noise and vibration will transfer in all directions wherever possible — under doors, through windows and through any types of errors or leaks. That sound will invade adjacent spaces if it's not sealed up appropriately."

This article originally appeared in the October 2017 issue of Athletic Business with the title "Noise pollution solutions for today’s fitness centers." Athletic Business is a free magazine for professionals in the athletic, fitness and recreation industry. Click here to subscribe.