Noise Control

• By Thomas G. Dolan
• 02/01/09

"What's most generally wrong in gymnasiums is an excess of highly reverberent surfaces which reflect the sound, amplify, and distort it," says Art Barkman, president, Sound Management Group, Hillsborough, NJ. What exacerbates the problem, Barkman continues, is that gymnasiums are rarely used for just one purpose. They are multipurpose spaces used for different sports, assemblies, lectures, music and dramatic performances, and classrooms. "It's difficult, and sometimes impossible, to adequately hear instructions, or even announcements at a basketball game," Barkman says.

Barkman likens the situation "to the old Grand Central railway station. Everybody was talking and there was a lot of loud noise. You might just arrive at a game and have no idea what the announcer is saying. It's not that you haven't heard it. You may have heard it five times, but you didn't understand it. There's a big difference between hearing and understanding. How many times have people thought they heard their names called at an airline terminal and went to the information desk to find that someone else was called?"

When the gymnasium space is divided up into classroom areas, there's often a lack of privacy, with distractions coming from the other areas. "What you have then is the cocktail party effect," Barkman says. "Everybody talks louder to be heard, and that, of course, only makes the situation worse."

Reverberation time (RT), Barkman explains, is a measurement of distortion, the actual time it takes for a sound to decay. An RT of 6, is a decent decibel count for a message to be understood. But in gymnasiums the RT can go from 9 to 11 or more. By contrast, the RT for a recording studio is a percent of a decibel.

Kenneth Roy, Ph.D., a senior research scientist with Armstrong World Industries, explains that an initial analysis of excess noise will show that it comes from one of three sources, equipment, the outside, and the people inside.

The background noise coming from the heating, ventilation, and other mechanical equipment is amenable to mechanical remedies, Roy says. For instance, you can analyze how the air is brought into the space, its velocity, the types of blowers, and so on. In some cases, larger air ducts might be used. Generally, a specialist will be able to pinpoint the cause and come up with a solution.

Noise from the outside might come from various sources, such as the facility having been built near a highway or an airport. These problems can be addressed with relatively straightforward remedies, such as increasing the thickness of the walls or insulation, or putting in double panes of glass in the windows.

But bring people into the gym and things get complicated. "A clap in the middle of the space can bounce off the ceiling and walls and floor and not necessarily on one plane," Roy says. "You get the echo effect, especially when you have a basketball bouncing up and down. But your real noise levels come when the space is filled with kids, sometimes screaming."

The right design, with appropriate balances of reflective and absorbent materials, could eliminate acoustic problems before the facility is constructed. But Robert Marshall, manager of marketing technical services for CertainTeed, maintains that "acoustics is a blind spot for most architects. I don't know if architecture schools are spending any significant amount of time on acoustics. For it's certainly not reflected in the gymnasiums that have been built or are being built."

Marshall reflects on a personal experience he had with this situation. "They built a high school my kid goes to, about a mile away," Marshall recalls. "I spoke to the architect all about the importance of acoustics. But, at the end of the day, when they expended millions of dollars on this project, the first thing they took out was the acoustical aspect. Ignorance on the part of school boards is a part of it. But it's primarily the failure of the architect to impress the board that he will not take a red pen to cutting out the acoustics." Yet Marshall also acknowledges that if any particular architect took a stand on this matter, the contract would be likely to go to an architect who went along with this cost savings measure.

Marshall argues that the investment would be worth it. For, in a good, better, best scenario, he estimates that the implementation of a good acoustic design would be a 100 percent improvement of the conventional approach. A better acoustical design would be about a 50 percent greater improvement, and the best option would represent about a 150 percent greater improvement. In terms of actual costs, Marshall estimates a good acoustical effort (including both design, materials, and labor) would cost one percent more than the conventional way, the better efforts three percent more, and the best option just 5 percent more. Although these percentages are small in themselves, Marshall points out that, when you're dealing with multi-million dollar projects, the actual dollar amounts on a budget sheet can still add up to a significant sum, which makes it an attractive target for someone whose primary focus is removing dollars from the budget. One is less apt to skimp with a shoddy HVAC system that is likely to easily break down. But acoustics can appear to be not that important or necessary a feature.

"Whenever we get an opportunity to speak with designers, we don't hesitate to do so," Marshall says. "We feel there is very little understanding of the nuances of acoustics. So we've taken to emphasizing the safety aspect. If there's an emergency and the students have to be evacuated from the gym, you want the PA system to work effectively, and the students to be able to hear the instructions clearly."

Marshall adds that "For years I've asked the question that if you're a designer and design for K-12, haven't you come across any generic designs or evolved one of your own for good, better, and best in terms of acoustics? That doesn't seem to have happened. No one is trying to build a better mousetrap. Acoustics is just not considered an important aspect of design."

Marshall wonders why there haven't been either local or national commissions that have tried to tackle this problem, not someone he says "who has his horse in the race," but rather an objective body of experts who can tackle this problem and provide some sort of blueprint. "There should be able to be someone who will advise you on the upfront costs," he says. "There have been studies on the effectiveness of various materials and their cost."

Good acoustics really don't cost that much, Marshall continues. And intelligent usage can minimize the cost. For instance, gyms often go up 20 to 25 ft. in the air, but absorbent material on opposing walls don’t really need to go up higher than about eight ft.

Different space usages also necessitate different solutions. For instance, if a stage is present on one end of the gym to be used for performances or assemblies, the opposite wall must be more fully absorbent than it might otherwise be.

"But, we find designers often don't want to make even small accommodations that would improve acoustics," Marshall says. "It's rare to find someone who will make a true commitment to acoustics. The best that happens is someone puts up something basically cosmetic, an acoustical panel here or there. It often comes down to a few dollars, like trying to use a fly swatter to fight a jet."

Barkman, however, sees a more positive aspect to this situation. He agrees that cost pressures affect architects. "Often times the architects we work with won't get a fee for incorporating acoustics into the design. And he's hesitant to ask the general contractor to go along, so there can often be a series of mark-ups he makes, which makes the original estimate be more," says Barkman.

Yet, on the other hand, he explains, "There are two types of gymnasium designs in the first place. One is simply a bad design. The other is basically a good design, without the acoustics, but the design is such that the acoustics can be later added inexpensively."

Barkman maintains that acoustics lie outside of the more common principle of paying more upfront and saving over the long term, or the opposite. "Accoustics is one area which you can often add later without tearing up the structure," he says.

There are now more innovative solutions than there were a few years ago. "In the old days, there were the full suspended ceilings," says Roy. "These were not a good solution. But now you have canopies, not simply covering the ceiling, but curved and highly visual in three dimensions. These get absorption from both sides."

Barkman mentions that panels now come in square edge, radius, or bevel styles. Hook and loop fasteners are used to easily affix absorbent panels to clean, smooth, or non-porous surfaces. There are baffles that feature eyelet hooks that make hanging simple. Suspension materials can range from decorative chain to unobtrusive fishing lines. "Old fashioned school banners work very well," says Barkman. "There are all kinds of inexpensive remedial features."

LEED for Schools "is one good thing that is happening," says Marshall. "We now have people asking questions about acoustics they haven't asked before. We may soon see the start of a trend in which those who do not incorporate acoustics into their design won't get the commission." That would be one message that is both loud and clear.