Posted on April 17, 2023
Every room has some element of “room noise.” Some of it comes from an HVAC hum, chatter from a hallway or another room, background music, or loud noise pollution like cars and train horns. All of this ambient noise impacts our concentration and reduces cognitive performance and other mental tasks. Sometimes the effect is more profound than we might think.
We all know someone who likes white noise to study, work, or sleep. White noise machines offer a way to “drown out” a lot of the background noise that impacts a room. Sound is additive, meaning any additional sound in a room is layered on top of the existing ambient noise. White noise and background music attempt to add a layer of control by “covering up” this environmental noise pollution. These auditory mental tricks can work for some people but not for those who prefer or need a quiet environment to do any complex task.
Building designers or owners often never consider a building’s background noise. In our efforts to create more humane, sustainable, and comfortable buildings, R.E. Dimond and Associates engineers have looked hard at background noise and its impact on building users.
The science of background noise and our ability to focus
Real-world noise tests by researchers show significant effects on our ability to concentrate, regardless of age or task. Researchers at the University of Alberta piped in ambient noise to adults in one experiment, then monitored brain activity and found:
“We were able to change brain activity during a cognitive task in a noticeable and reproducible way, simply by playing outdoor sounds in the background,” said Scanlon, who conducted the study under the supervision of Kyle Mathewson, assistant professor in the Faculty of Science. “These findings show that our environment affects how we perceive the world around us—and means that much of what we know about the brain is oversimplified since it has primarily been researched in a laboratory setting.”
They also note our brain is working hard nearly constantly to filter out the adverse effects of background noise like traffic and verbal chatter.
Negative impacts on reading comprehension, workplace safety, and task performance
OSHA says background noise increases people’s stress levels, usually by reducing the amount of cortisol in our bodies. This leads to aggravated stress, high blood pressure, coronary disease, ulcers, and headaches. Further, they note, “continued exposure does not lead to habituation; in fact, the effects worsen.”
In most cases, we never adjust to the background noise levels. This has distracting effects on our ability to work safely. The result can be employees operating heavy machinery without hearing cues, failing to comprehend warning labels or signs, and reduced productivity.
Ambient noise and the impact on schools and student performance
The perceived disturbance of students talking in a hallway is just beginning to be understood, but early science is clear: noisy environments negatively influence student performance. A significant reduction in noise pollution from HVAC units, ambient sounds, steam, and electrical hum, can improve a student’s cognitive functions. Further, improvements in acoustics—like being able to hear a teacher from far away—can increase what students hear from teachers by as much as 50%.
So much so, there is a Classroom Acoustics standard and ANSI Standard S12.60:
“The maximum reverberation time in an unoccupied, furnished classroom with a volume under 10,000 cubic feet is 0.6 seconds, and 0.7 seconds for a classroom between 10,000 and 20,000 cubic feet. The maximum level of background noise allowed in the same classrooms is 35 decibels (dBA).”
The Acoustical Society of America (ASA) believes background noise from heating and air conditioning systems is worse than sound levels from traffic or other exterior distractions. They looked at test scores from students in 58 empty second and fourth-grade classrooms, and what they found was kids who spent most of their time in the louder classrooms produced lower test scores on standardized reading comprehension task exams.
In another study, the ASA repeated the volume collection in 67 empty classrooms in Nebraska public schools, but their results varied. Fifth-grade students scored lower in louder rooms, but the third grades saw no relationship. Those taking math exams showed no difference in scores.
In other words, long-term noise exposure diverts mental resources for everyone but harms some more than others.
Previous studies suggest children in noisy environments have diminished speech development, particularly at the elementary school level. Children are also less able than adults to use spatial cues to separate things they should hear—like a teacher—from noise, like a rattle in a heating or cooling unit. This signal-to-noise ratio reduction reduces cognitive performance at a critical time during brain development.
Memory and non-auditory task performance like reading is also reduced and has a negative effect on problem-solving and retention that can last into teenage years and adulthood.
Designing classrooms and a work environment with quieter background sound
The truth about noise levels and performance is likely somewhere around what we all instinctively think it is: a quiet space is better than a loud space for focus for most people most of the time. Acoustics also matter, so students and workers who listen to teachers and teammates hear what they say, understand it, and put that information to good use.
Our engineers tackled a similar challenge at music instrument distributor Sweetwater, where the sound of outdoor HVAC units was interfering with the highly-tuned ears of musicians.
Buildings can be designed to improve these critical cognitive functions. We look to design schools, workplaces, and other facilities like theaters around three characteristics:
- Heating and cooling noise criteria, with care given to reduce vibration, control air speed, and minimize holes, gaps, and air leaks. This also has the side effect of lowering resource loss and improving comfort uniformly across a building. We did a project with Sweetwater Music that reduced HVAC noise so audio professionals—who are listening to everything—don’t notice the HVACs at all.
- Sound transmission, with a focus on building barriers, walls, and windows that reduce known noise, such as traffic, a gymnasium, or a conference room.
- Good room reflections, with the intent to design a room for its purpose. This includes the room acoustics and understanding that a choir room and a classroom or a small lecture hall, theater, and conference room are all unique spaces with different needs and impacts on other spaces. Rooms that use soft surfaces, including furniture and curtains, can quickly reduce reflectivity.
A lot of noise must be dealt with at its source. Curtains and soft chairs go so far if a large air conditioner is poorly fastened to a roof. But engineering spaces to reduce noise delivers reduced background noise levels, less stress, improved concentration, more focus, and a better, distraction-free environment.
