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Contemporary solutions in ceilings and acoustics
Kenneth P. Roy senior principal research scientist with Armstrong Ceiling Systems, on contemporary solutions in ceilings and acoustics.
Hi, I'm James Pease and this is Take5, Building Operating Management's podcasts on topics of interest to building and facility executives.
It’s a common problem, and a major irritant. You enter a beautifully rehabbed restaurant, for instance, with hardwood floors, a high tin ceiling and reflective walls in a rectangular space. Halfway through your salad, you realize that your party is practically shouting to be heard above the general roar of the room, making the room, of course, that much noisier. Clearly, acoustical design wasn’t very high on the list of priorities in creating and decorating the space.
This same issue rears it’s head in the business place, the classroom and healthcare facilities where poor acoustics may create problems more serious than a spoiled dining experience. It’s increasingly acknowledged that acoustics are an important element of IEQ
With us today is Kenneth P. Roy, senior principal research scientist for acoustic technologies worldwide with Armstrong Ceiling Systems.
Thanks so much for being here with us, Ken
[Pease] There has been a move toward more open or exposed building structures. How does this affect acoustical performance in a space?
(Roy) The drive to have more of an open visual or exposed structure space generally involves opening up the vertical height. Whether the architect or owner chooses to expose the HVAC system or whether air is brought in through the underfloor frees them from the belief that a ceiling is necessary in a space. That's an aesthetic preference, but we need to recognize that an acoustical ceiling performs the added function of controlling noise & reverberation within the space. If there is not a continuous ceiling, we have to remember to include alternate solutions for the noise and reverberation control. Typical solutions being developed at this time include freestanding cloud elements, independently suspended canopies, baffle and curtain systems – any way to add sound absorption in the space in a distributed mode, while still allowing for that exposed, open look. In the traditional suspended acoustical ceiling, the measure of the absorption is based on the NRC coefficient, which is measured on a square foot basis - any of the discontinuous solutions such as clouds and canopies are represented by the sabin, which are units of absorption for the entire system. Again, in this way, you're able to maintain a great visual effect while still providing sound absorption, which will enhance the acoustical performance of the space.
[Pease] If the aesthetic doesn’t allow for a ceiling treatment solution, for instance in the case of highly decorative tin or plaster, does that also conform to your alternatives for dealing with non-continuous ceilings? Will opposing reflective surfaces with acoustically absorbent materials help?
(Roy) Sure. You can still have an open view of the ceiling if you’re not covering more than half of it with clouds or canopies, but you might not achieve enough absorption with that. If the walls are 15 feet high or higher – 12 feet is borderline – you need to consider sound absorption on the walls because a lot of the sound bounces horizontally and never gets to the ceiling itself or the floor, which might be carpeted. You only have to treat two adjacent walls in a rectangular room because the sound is either going to go right to left or front to back; one of the parallel walls will absorb the sound.
[Pease] Sustainable practices are impacting every area of facility design. Do you foresee LEED requirements incorporating acoustics?
(Roy) Yes, it has already begun. Acoustic standards are starting to be addressed by a few of the rating systems (LEED for Schools, Green Guidelines for Healthcare, Australia's Green Star ), the question becomes "Just how well are we doing with the acoustic outcomes such as speech intelligibility and speech privacy, or noise distraction and annoyance?"
An indication of this can be found in an ongoing research program at UC Berkeley's Center for the Built Environment (CBE). Post-Occupancy Evaluations have been administered in over 200 buildings and to over 35000 respondents inquiring about the indoor environmental quality. Approximately 10% of those buildings have either been LEED certified or "self-nominated" green buildings. On average, LEED buildings have been found to be ’higher performing’ in terms of factors such as IAQ which are directly addressed by LEED, but slightly 'lower performing' on acoustics, possibly since LEED does not directly address this issue. Actually, in all buildings surveyed, the level of acoustic satisfaction is the lowest performance factor of all the surveyed interior environmental factors. Acoustics has also been recognized in a recent Platinum certification of a LEED for Existing Building. Superior acoustics was demonstrated in an open plan area leading to the award of an innovation in design credit. The benefit will be increased health and productivity of the building occupants of any space that incorporates the correct architectural design. An appropriate long-term solution to having good acoustical outcomes would be to instill an understanding of the ’need for good acoustic design practices’ within the Green process.
[Pease] Why? Does the larger surface area resisting greater air pressure translate directly into increased velocity?
[Hardy-Pierce] A parapet wall protects the roofing system, and when the wind tops the roof, a parapet wall reduces the uplift pressure on the membrane by moving the fastest wind above the membrane.
Finally, large openings, such as large truck bays, in the building can really cause problems for the roofing system because a wind, blowing into the opening has to “go” somewhere”… when this happens, it can greatly increase the pressure on the roof because not only is the wind topping the roof edge and applying pressure, but the “wind” from inside is pushing up from the underside of the deck at the same time.
[Pease] In thinking about schools and noisy classrooms, do you see the use of amplification in the classroom an alternative to offsetting the noise? Should teachers be wearing mics?
(Roy) Not really - and here’s why. You first need to develop good architectural acoustics within the space. This ensures that the sound field in the classroom is adequate for good speech intelligibility between teachers and students and anyone in the space. Although sound reinforcement systems have been used in schools to offset architectural improvements, you would find that the sound reinforcement only makes the sound louder - it doesn’t improve the quality. If the problem is architectural in nature, due to the lack of sound absorption and therefore high reverberation times, the basic issue at hand has not been addressed. A more successful solution would be to fix the sound problem by adding adequate sound absorption with a high NRC suspended ceiling.
[Pease] The flip side of reducing noise is – and I know this is one of your areas of interest and research – maintaining privacy when the noise is minimized in public or semi-public spaces. What are the issues with this in regard to healthcare facilities, for instance?
(Roy) Good speech privacy means not having private conversations overheard. That’s what we focus on in healthcare. In the office environment, we’re usually talking about minimizing distractions. But in healthcare, we’re trying to maintain the confidentiality of the doctors’ conversations with their patients or keeping administrators from being heard in, for instance, a reception area. Having good speech privacy often demands having an electronic masking system. You want to be as robust as possible in the architectural design of the space especially in the newer clinics that are in malls, for instance. Where there is a great deal of reconfiguring of the space, walls often only go as high as the ceiling tile, so you need to make sure you have a high performance ceiling tile in place and that you have an adequate wall structure to limit the intrusion of sound into or out of the space. But whether you can actually hear and understand that intruding sound depends on how loud it is in relation to the background noise and you can’t leave it up to chance what the background noise is going to be based on the HVAC system. You have to introduce electronic masking sound. You handle the things close by through the architecture of the space; you handle things far away by the background noise in the space. If you take all three components – absorbing the sound, blocking the sound between spaces, and covering up whatever’s left over – you have what we call the A-B-Cs of acoustic design. If you can balance all those three parts, you’ll achieve adequate speech privacy.
[Pease] Thank you so much for spending this time with us Ken.
Our guest today has been been Kenneth P. Roy, senior principal research scientist with Armstrong Ceiling Systems.
I’m James Pease and this has been Take5.
Kenneth P. Roy, Armstrong World Industries
Have a question about acoustics? Contact Ken at firstname.lastname@example.org
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