A Sound Affect on Human Centered Design

I was once told good (and bad) acoustics is something you experience; something you can feel, even if you don’t know what it is. I am always impressed at how real this experience can be.

Research shows that people work more productively, communicate and learn more effectively, and heal more efficiently in environments with good acoustics.

Recently, Jill Robles, the Ecophon Architectural Sales Manager in New England, and I had the pleasure of working with the Institute for Human Centered Design (IHCD) in Boston, Massachusetts.  The IHCD is an international non-governmental educational organization committed to advancing the role of design in expanding opportunity and enhancing experience for people of all ages and abilities through excellence in design.

A large lobby area outside of a conference room is utilized frequently for meetings.  It is a great space for informal gatherings after presentations but the acoustical condition made it uncomfortable and difficult to hear. Conversations can be a challenge without proper sound dampening because of heavy reverberation and increased sound pressure levels.

Prior to our “acoustical intervention”, members of the IHCD team were skeptical that the acoustical challenge could not be overcome, and that any acoustical solution might resemble that of an “ugly burlap sack”

Our solution? Shaped, free-hanging, acoustical sound-absorbers hung from the existing gypsum ceiling at varying levels to enhance the contemporary and spirited design in an area that has many acoustically reverberant surfaces. We took simple before and after decibel (db) readings, and the sound pressure levels decreased by 13 db when people were talking softly. It may not sound like a lot, but a 2-3 db reduction is like having two car engines running side by side and turning one of them off!

Though acoustics was the primary reason for the treatment, these noise absorbing systems were far from the feared “burlap sack”. Members of the IHCD staff commented on how they served as artwork. The shapes and levels complimented the suspended lighting, and even allowed some flexibility in how light was dispersed.

But the true test was during a presentation weeks later, co-hosted by the International Interior Design Association (IIDA), Ecophon, and CertainTeed. Attended by more than 60 guests from the Architectural, Design, Acoustical Engineering, and Interior Design Communities, the presentation by European speakers discussed how acoustics impact people based on research from around the world.

After the presentation, the guests mingled, chatted and relaxed. The most interesting part is that everyone congregated in the area that received the acoustical treatment, while the other areas in the facility were empty. To me, this demonstrates a good acoustical experience… nobody knows why they feel more comfortable in a space, but they naturally communicate better in it.

Combine Fiberglass and Mineral Fiber Ceiling Panels for Top-Notch Acoustic Control

Choosing the right ceiling panel material for a project makes a huge difference in managing the acoustical response of a room. An acoustical design strategy needs to include an adequate balance of both sound absorbency and sound attenuation.

Derived from ASTM C 423, which is the predominant standard for sound absorption in the U.S., noise reduction coefficient or NRC is a scalar representation of the amount of sound energy absorbed by a particular test sample. It is calculated as an arithmetic average to the nearest 0.05 over a limited frequency range (250 Hz, 500 Hz, 1,000 Hz and 2,000 Hz). In a simplification of the concept, an NRC of 0 indicates total reflection, while an NRC of 1.00 indicates total absorption.

Ceiling attenuation class or CAC is the measurement of the ceiling’s ability to block sound in a closed space from passing up into the plenum and transmitting back down into a neighboring closed space under the same plenum. The single number for CAC is derived from ASTM E1414. Ceilings with a CAC less than 25 are rated as lower performance, while those with a CAC greater than or equal to 35 are considered higher performance.

Fiberglass is more effective at quieting a room than is mineral fiber, as it performs well in both high and low frequencies. Mineral fiber tends to excel in high frequencies but lose absorption in lower frequencies. Yet, the low density of fiberglass ceiling panels, which makes them extremely resistant to moisture and sagging, at the same time limits their ability to contain sound. Consequently, fiberglass ceiling panels typically have a very high NRC, but a CAC that is on the low end.

Mineral fiber ceiling panels are denser and heavier than those made from fiberglass. It is that higher level of density that make them reasonably effective sound attenuators (meaning they impede the transmission of sound from room to room). With good sound attenuation and average sound absorption, mineral fiber ceiling panels tend to have a higher CAC and lower NRC than their fiberglass counterparts.

Building and design professionals can maximize acoustic control by combining a sound-absorbing ceiling panel with one that halts the transmission of sound waves; hence the composite ceiling panel.  With a composite panel, manufacturers such as CertainTeed laminate a layer of sound- absorbing material [fiberglass] to a layer of sound-attenuating material [mineral fiber]. The resulting product is sold and installed as a single ceiling panel. This greatly simplifies operations for the architect and contractor and provides the end user with the best of both worlds in acoustic control for many years to come.

Individually, fiberglass and mineral fiber ceiling panels have their own ways of controlling excess noise. However, when used together they produce top-notch acoustical results in a space. Whenever acoustics is a design requirement, allowing fiberglass and mineral fiber to work together in the form of a composite panel is an excellent choice.

Robert Marshall is Technical Services Manager, Ceilings for CertainTeed Corporation