Acoustics – Designing Classrooms for Optimal Learning

Santa Monica Public LibraryWhat impact can you as the designer bring to a classroom setting given that you are not going to be teaching?  One of the things you potentially bring is the ability to impact the environmental acoustical value of the space.

The 21st Century classroom is a more diverse place than ever before. With the mainstreaming of children with learning disabilities, physical challenges and language barrier issues, it is more important than ever to have an acoustically efficient environment. To create a design which does not addresses the lowest common denominator just seems wrong.

This gives students a better chance of staying engaged. It is especially critical where younger students are concerned (K-5). They do not yet have the skills to fill in the words that are lost when listening to the teacher in a less-than-adequate acoustic environment.

I worked in ceiling construction earlier in my career and built hundreds of school classrooms knowing all the while that they were poorly designed spaces accountable only to the installed cost per square foot. I then moved into working with the architectural community in an effort to bring a better focus on the power of and necessity for efficient acoustic design. I have observed through numerous academic studies that the attention to acoustic design in classrooms has a significant impact on learning for all students; but especially early learners. I was also afforded the opportunity to observe this need for acoustic design close-up as the parent of an autistic child attending a public school.

Thanks to LEED taking an active part in acoustics and environmental design, this topic is now required for certification in a LEED for Schools project. It is our responsibility as designers, specifiers and advocates to put a human face on the critical importance of this topic.

I will be teaching a webinar on Classroom Acoustics on Tuesday, March 11, from 12:00 – 1:00 pm. I will cover issues such as: Signal to noise ratio – reverberation time – speech intelligibility testing – how all these metrics and academic testing have shown that a quieter environment is a better learning environment – and more. 

If this is a topic of interest to you, take advantage of this free webinar by registering here: Ceilings: Classroom Acoustics (GBCI Approved)

 

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