By Niklas Moeller, and Viken Koukounian, PhD, P.E.
While sight is generally prioritized over other sensory modalities during building design, the completed structure’s aural qualities do not simply provide a neutral backdrop for activities—a fact apparent to those who managed to carve out “quieter” home offices during the pandemic, only to be called back to noisy, overstimulating commercial spaces.
To tap into the built environment’s full potential to improve well-being, one needs to better understand not only how noise negatively affects occupants’ physical and mental health, but the ways in which “the sonic aspect of buildings can be intentionally articulated to achieve a richer, more satisfying built environment: one that responds to the ear as well as the eye.”1
Auditory health effects
Hearing is a historically undervalued and underserved sense, at least within Western societies. It was not until the mid-20th century—as public awareness of the need for stricter occupational health and safety guidelines grew—that the requirement to preserve it garnered widespread support. Numerous studies subsequently demonstrated strong correlations between sudden or sufficiently prolonged exposure to higher noise levels and temporary or permanent hearing loss, which is generally understood to mean damage to the hairs or nerve cells within the ears, affecting their ability to transmit information to the brain. Other potential consequences may involve tinnitus, characterized by ringing or other “phantom noises” in the ears, and hyperacusis, which refers to the increased sensitivity to ordinary sounds.
Today, most people are well-acquainted with the auditory health effects of high noise levels, as well as the associated “safe limits” established for workplaces. Basically, the risk of hearing loss is immediate when the noise level approaches or exceeds 120 decibels (dB) (e.g. from an explosion), while impairment due to lower levels (e.g. from machinery) usually requires longer exposure; for example, a 15 minute exposure to 100 dB or a two-hour-long exposure to 90 dB.2 Across Canada, the criterion level, indicating the steady noise level permitted during an eight-hour work shift ranges from 85 to 90 A-weighted decibels (dBA), depending on the applicable federal and provincial regulations.3 As noise increases above this level, the allowed exposure time decreases.
Non-auditory health effects
Fewer people are aware of the potential non-auditory health risks posed by lower-level noises, those below the established thresholds associated with hearing impairment. Over the past decades, researchers started exploring the impacts of various sources (e.g. road, rail, and airplane traffic), and the results are mixed. As a general, non-specific stressor, noise has been found to have non-auditory health effects—such as changes in hormones, sweat response, metabolism, heart rate, and blood pressure, as well as outcomes related to its disruptive effect on sleep and immune response—but not consistently. Further, it is difficult to conclusively link to, for instance, the development of heart disease, which can also be linked to other health-related factors.
This is not to say there are no such adverse impacts; in fact, some experts maintain the question is no longer whether noise causes cardiovascular disease, but to what extent.
Noise sensitivity
Research consistently demonstrates noise level alone is not a sufficiently strong indicator of potential health consequences. Additional characteristics such as frequency, predictability, complexity, duration, and meaning of the noise in question, as well as those of the listener’s acoustic environment (including ambient or background spectra and levels), need to be taken into consideration, as well as factors related to the listener themselves—perhaps first and foremost, their sensitivity to noise.
