Gary Madaras, PhD
New, modern learning spaces are built to promote collaboration and inclusion by fostering a sense of togetherness and providing equal access to knowledge and resources. Specifying interior building products to achieve optimized acoustics is essential to support educational facilities’ design goals, and the teachers, staff, and students who depend on them.
Decades of research has proven loud noise can result in hearing loss, increased heart and respiratory rates, disruptions, and higher perceived stress levels. Noise does not need to be excessive to affect one’s well-being and learning capabilities. The acoustics inside classrooms determine whether students and their teachers can understand one another. This not only has an immediate impact on comprehension and retention, but also influences test scores, students’ morale, teachers’ job satisfaction, absenteeism, and short- and long-term health problems.
The benefits of a positive acoustic experience extend beyond traditional classrooms. Their relevance can be heard in gyms, aquatic centres, auditoriums, cafeterias, offices, theatres, band rehearsal rooms, recording and broadcast studios, fabrication shops, media centres, and more.
A Canadian national standard has been defined to address acoustics in schools, colleges, universities, libraries, and other centres of learning. The 2015 National Building Code of Canada (NBC) incorporated acoustic requirements for residential dwellings, but not for educational, commercial, or institutional buildings.
At the provincial level, only Alberta has acoustic performance requirements in its 2020 Technical Design Requirements (TDR) for Alberta Infrastructure Facilities. The importance placed on incorporating high-performance sound absorption into its learning facilities is summarized by the following statements:
Integrate surfaces with high acoustical absorption properties into the architectural design. This can reduce acoustical reverberation, decrease noise, and create comfortable environments with good speech communication.
Provide ceiling tiles with high sound absorption, acoustical roof deck, and sound-absorbing block wall. These surfaces are typically easy to refresh, are abuse-resistant, and cost-effective.
Open plan spaces (e.g. classrooms, offices) require ceilings with very high sound absorption; minimum standards may be too low for some situations.
Provide high quality flanking walls and ceiling baffles. This mitigates against future acoustic degradation if acoustic panels are replaced with conventional construction.
Alberta’s TDR also provides more detailed acoustic performance requirements. In classrooms, the maximum permissible reverberation time (RT) is 0.60 seconds. The minimum noise reduction co-efficient (NRC) overhead is 0.55, which is very low, and would not achieve the maximum permissible RT. The lower NRC allows for designs where most of the sound absorption is instead being provided by the walls and floor. If the ceiling was the only sound-absorptive surface in the classroom, its NRC would need to be 0.75 or higher, depending on the ceiling height to achieve the required RT.
Beyond classrooms, Alberta’s TDR requires common areas to have ceilings with a minimum NRC of 0.70, providing good sound absorption in these active gathering spots. Music practice rooms are required to have even better sound-absorbing ceilings with a minimum NRC of 0.80.
Without acoustical guidance at the national or provincial levels (except for Alberta), some learning institutions have opted to develop their own acoustics standards. Since British Columbia does not offer a province-wide, uniform guideline addressing acoustic performance in educational facilities, the University of British Columbia (UBC) has developed its own language, which is a part of its Learning Space Design Guidelines.
The guidelines refers specification, design, and construction professionals to the Acoustical Design Standard for UBC Classrooms. These acoustical standards emphasize:
University classrooms are acoustically critical spaces in which verbal communication is crucial for teaching and learning. Non-optimal acoustical conditions in classrooms result in impaired verbal communication between teachers and students, impaired teaching and learning, and teacher voice problems. Students and instructors experience broken concentration, frustration, and fatigue. Students have difficulty hearing other students ask questions. The problems are particularly acute for hearing-impaired people, and those using a second language.
It continues, noting that “controlling and optimizing the acoustical conditions in a classroom, or other rooms for speech, involves three fundamental considerations: promoting high speech levels, controlling background noise, and optimizing reverberation.”
UBC assumes its existing “classrooms have ceiling absorption—often form all or part of a suspended acoustical ceiling—in order to control the classroom reverberation, in-class student-activity noise, and impact noise from spaces above the classroom.” RT requirements vary between 0.45 seconds for critical classrooms and 0.85 seconds for larger noncritical classrooms. More specific guidance on ceiling NRC ratings is not provided.
For most of Canada, acoustic requirements for the design and construction of learning facilities are non-existent. In May 2019, the Speech-language and Audiology Canada organization published a position paper on classroom acoustics that said, “Canada and its provinces and territories must adopt changes to their respective building codes to include standards for classroom acoustics. These standards are essential to optimize learning, teaching, overall health, and quality of life.” The paper also referenced previous research indicating “children often work in classrooms with noise levels equal to or higher than the level of the educator’s voice, which leaves students listening to a ‘sea of noise.’”
Due to the absence of acoustics standards for learning spaces in Canada’s codes, designers, specifiers, and contractors are turning to a number of other options.
Start with functionality, volume, and shape
When embarking on the acoustical design of a learning facility, first consider these basic questions at the earliest stages of each room’s design.
What is the purpose of the space and what activities will take place in it? Rooms and spaces can be categorized into those for speech, focus, activity, or music.
Who will be using the space and how important are speech intelligibility, privacy, and freedom from disruptive noise? Will the users’ sensitivity level be high, moderate, or low?
How much noise will be generated from inside the room and its adjacent spaces, such as from a lively meeting or noisy equipment? Will the noise level be high, moderate, or low?
The core acoustic function of any room or space affects its natural shape and size. The finishes and their placement within the room also affect whether it is suited acoustically to its function. Glass, metal, stone, wood, and concrete are typically sound-reflective and can be used beneficially in a lecture hall to passively amplify the speaker’s voice. If they are used too liberally though, they result in excessive reverberance and can make speech difficult to understand. The most important factor, and the focus of this article, is the specification of the sound-absorbing finishes or treatments in relation to the function and size of the room.
Rooms for speech
Rooms for speech vary in size and function from a 10-seat meeting room and 100-seat lecture hall to a 1000-seat theatre. The primary acoustics goal in each is high speech intelligibility. Making speech intelligible inside rooms requires a loud sound source and low noise levels; in other words, a high signal-to-noise ratio. A well-designed speech room can hold listeners’ attention even as the speaker moves, turns away, or is blocked from direct line of sight and sound.
As a speech room increases in size, it becomes more difficult to maintain speech intelligibility and more critical to optimize the acoustics of the room. It is necessary to view the room as a passive amplification system. Larger speech rooms have lower signal-to-noise ratios because the average listener distance is greater and the speech signal has to travel farther. Therefore, speech rooms should be as small as practical for the intended capacity. The goal for the shape of the room is to minimize the average speaker-to-listener distance. The ceiling should be as low as possible to limit the volume of the room and decrease the amount of acoustic treatments needed to control reverberance. This is why a number of good speech rooms are fan-shaped with very low ceilings.