By Kathi Mestayer
Yes, it does. In fact, noise stresses most people (and even many animals).
But what is noise? My favorite definition is in the glossary of “Sound Matters,” a 2012 publication of the General Services Administration’s (GSA) Public Buildings Service:
“Noise: Any undesired sound.”
So, if noise is undesired, it’s not that surprising that it’s stressful, right? In an article in Noise and Health, “Is There Evidence That Environmental Noise Is Immunotoxic?,” the author, Deepak Prasher, doesn’t mince words: “It is clear that noise is a stressor. The physiological response to noise as a stressor is no different from any other nonspecific physical stressor.” So, how does noise stress us out?
Danger! Danger! Warning! Warning!
Noise triggers a stress response in the amygdala, a region of the brainstem. Our amygdala learns, over time, what sounds might signal impending danger. When one is detected, the amygdala triggers a release of cortisol (a stress hormone) and an involuntary startle reaction. In his book, The Universal Sense: How Hearing Shapes the Mind, neuroscientist Seth Horowitz explains, “The auditory startle circuit is a very successful evolutionary adaptation to an unseen event. It lets us get our bearings and get the hell out of there, or at least widen our attention to figure out what the noise was.”
Cortisol affects us in many ways. According to Prasher, “In the acute stress reaction to an immediate threat, the secretion of stress hormones results in increased heart rate and blood pressure, a rapid release of energy in the bloodstream, reduced metabolism with a decrease in salivary and gastrointestinal activity, reduction in sex hormones, and activation of some immune functions.”
Over time, stress (often from transportation and industrial noise) can be particularly toxic. “This model of reactivity in terms of noise-induced stress has been implicated in the development of disorders of the cardiovascular system, sleep, learning, memory, motivation, problem-solving, aggression, and annoyance,” Prasher writes. If you think you’re getting used to that highway noise, think again.
Hearing loss and noise
So, people with hearing loss must be less sensitive to noise, right? Unfortunately, no—less hearing doesn’t mean higher noise tolerance. Research has been done on noise sensitivity and whether it correlates with a person’s audiogram. Here’s a summary of findings from the 2012 issue of Noise & Health:
“In the study of Stansfeld (1992), no significant differences were found in noise sensitivity between those with normal threshold of hearing and those with threshold impairment according to pure tone threshold audiometry. Likewise, Ellermeier et al. (2001) found no significant differences between two groups of low and high noise sensitivity in threshold levels, intensity discrimination, auditory reaction time or exponents for loudness functions. Our finding that the average hearing thresholds did not differ in noise sensitive and non-noise sensitive subjects is in concordance with previous studies.”
Anecdotally, this matches my audiologist’s observation that noise sensitivity is not correlated with our degree of hearing loss. “I always have to do a ‘sudden noise’ test with every person whose hearing aids I program before they leave my office. I can never predict who’s going to jump out of their skin and who’s not,” she says.
In case you’re wondering, I jumped.
Staff writer Kathi Mestayer serves on advisory boards for the Virginia Department for the Deaf and Hard of Hearing and the Greater Richmond, Virginia, chapter of the Hearing Loss Association of America. This is adapted from her reader-sponsored work, “Be Hear Now."