We understand that the built environments where we live, learn, work, play and heal can impact our health, well-being and functional performance. Knowing this, we seek to adapt these environments to support our physical comfort preferences, especially visual, thermal, hygienic and ergonomic factors. At home, we can paint the walls, display art, and select comfortable furniture and lighting. At work, we adopt ergonomic workstations and personalize our workspace. New technologies allow us to tune temperature, and the intensity and color temperature of illumination. The pandemic has prompted enhancements to ventilation and filtration to improve hygienic comfort (indoor air quality). The one factor that is difficult for individuals to control is aural comfort, and the impacts are significant.
Our brain is evolutionarily wired to continuously monitor for sounds that alert us to danger, both when awake and asleep. Even a short period of time in a loud environment increases blood pressure, while long-term exposure to noise can lead to cardiovascular disease. Excessive noise also impacts mood and increases stress, affecting personal and professional relationships and contributing to disease. Environmental noise is one of the primary detractors to restful sleep, impacting the duration, depth, and quality of sleep with significant health and safety impacts. Children are particularly at risk from noise pollution as loud environments at home and in school lead to poor concentration and cognitive performance, and impaired communication and speech development.
Acoustically comfortable environments are best achieved in the design of spaces as control measures are ideally integral with wall, floor, and ceiling assemblies. Retrofits can be very challenging, limiting mitigations to noise-canceling headphones and ear plugs. Thoughtful design to control undesirable noise and reinforce sound quality is critical for human performance, health, and wellness. This is especially true in open-plan offices, classrooms, and apartments, and should be considered in other space types as well. The primary sources of noise contributing to poor indoor acoustic comfort include:
- Background noise—Vibration, fan noise, and air movement from HVAC systems and other equipment can produce high levels of constant or intermittent ambient noise, interfering with concentration and communication. Noisy air-conditioning units that kick on and off, humming fans, and whistling air vents are frequent sources of complaints.
- Sound transmission—Sound from activities in adjacent spaces and impact vibration from the floor above (e.g., footsteps) transfer through walls and ceilings and create disruptive noise pollution. Sound transmission is not limited to horizontal or vertical adjacencies, as it effectively travels over distance through building structures and voids.
- Reverberation—While reverberance can be a positive thing for musical performance, echoes and prologued reverberation can impact speech intelligibility and lead to miscommunication. This is a significant issue in spaces like classrooms where a teacher’s voice must be heard clearly by all students, and in open office environments where the reverberation of multiple conversations can create a cacophony that impedes communication.
Identification of offensive noise sources and integration of acoustic design mitigations should occur early in the design phase. Acoustical consultants can provide guidance on the most effective customized solutions, but general guidelines and performance standards can be found in sustainability and wellness ratings systems. LEED for Schools includes a Minimum Acoustic Performance prerequisite that sets performance thresholds for HVAC background noise, exterior noise intrusion and reverberation time in core learning spaces. LEED also has a broadly applicable Acoustic Performance credit that sets enhanced targets for HVAC background noise and sound transmission between adjacent spaces.
The WELL Building standard dedicates an entire concept area to acoustic comfort. The nine features in the Sound concept range from general strategies like sound mapping to separate quiet and loud zones, to detailed performance standards and verification requirements for background noise, sound transmission, reverberation and other technical facets of acoustic design.
The basic acoustic design principles to meet these standards include:
- Plan space adjacencies with acoustics in mind. Locating noise-generating spaces away from acoustically sensitive spaces is a simple and cost-effective way to minimize future conflicts.
- When conflicting adjacencies cannot be avoided, use buffer spaces, such as storage rooms, between the two acoustically sensitive rooms or between a noise-generating space and an acoustically sensitive space to reduce the costs of upgraded wall assemblies.
- When the previous options are not possible, provide a special sound isolating assembly that addresses the specific sound source. For example, spaces that generate higher sound levels, such as mechanical rooms or music rooms, should have STC ratings of 55 to 60 or higher. While a typical insulated wall with a single layer of gypsum board on each side may provide sufficient privacy for speech at normal conversational levels, to reduce intrusive music with bass sounds, a heavier wall system may be required. We can assemble special wall, window and floor/ceiling systems to reduce noise sources with specific loudness and sound spectra.
- For shared or collaborative spaces, such as open offices or open plan classrooms, carefully design layouts of workstations or group learning areas to direct the sounds of people talking away from each other to reduce disruptions. Acoustical barriers are also effective means for obstructing direct sound paths between a person who is talking and a person who is trying to focus on a task.
- Place sound absorbing finishes in strategic locations to reduce reflected and reverberant sounds so that people can be heard clearly without having to raise their voices. Adhering to the reverberation time guidelines from LEED and WELL can reduce noise levels and so that sounds don’t reflect off interior surfaces and amplify noise.
Current design trends featuring large areas of glass, smooth, hard wall surfaces and exposed ceiling structures (such as mass timber and metal decks) can lead to increased noise levels and sound transmission. Early consideration of acoustical design strategies and technologies complementary to these architectural features can create a ‘sound’ design for aural comfort and decrease undesirable noise pollution. Integration of acoustics into the design of spaces is critical to health, comfort, well-being and productivity.
Alan Scott, FAIA, LEED Fellow, LEED AP BD+C, O+M, WELL AP, CEM, is an architect with over 30 years of experience in sustainable building design. He is a senior consultant with Intertek Building Science Solutions in Portland, Ore. Hyun Gabriel Paek, INCE, ASA, is an acoustical consultant with 26 years of experience and a senior consultant with Intertek Building Science Solutions in Orlando, Fla. To learn more, follow Scott on Twitter @alanscott_faia.