It was foggy this morning, after heavy rain last night. The fog made everything seem extra quiet, but was it really extra quiet, or did it just seem that way? Steven Ackerman and Jonathan Martin, two professors in the Department of Atmospheric and Oceanic Sciences at the University of Wisconsin-Madison, explain on their popular science blog The Weather Guys how fog affects sound:
Fog is made of tiny droplets of water. Sound waves interact with small droplets in such a way that sound undergoes attenuation and dispersion. … Attenuation by sound waves in fog is a function of the frequency, or pitch, of the waves. This is why fog horns have a very low pitch, because their sound will travel farther than a screeching sound. (1)
I heard no fog horns this morning, just birds and the water dripping from the trees, and it was so peaceful. I am sensitive to sound, and find silence very restorative. Not all sounds bother me equally; it is especially uninterrupted machine noise—leaf blowers, weed whackers, generators, air conditioners, compressors, highway traffic, you get the picture—that I find hard to bear. I know that some people are so used to being surrounded by city noise that they find silence uncomfortable, but my desire for silence has only grown over the years. (For a good documentary on noise pollution and the value of silence, see The Pursuit of Silence.)
I feel fortunate that I am able to experience silence on Salt Spring Island. Not all the time, of course, as we are accessible by road and thus cars, there is the occasional floatplane or helicopter overhead, the fridge hums, and so forth, but there are moments when, listening as intently as I can, I hear only the blood rushing in my ears. (Or, on a sunny day, sitting outside, I can hear the wasps chewing the deck!)
Unfortunately, many people have few opportunities to get away from noise, and noise pollution is unequally distributed. In the United States, environmental health researchers Joan Casey, Peter James, and Rachel Morello-Frosch found that
in both rural and urban areas, affluent communities were quieter. Neighborhoods with median annual incomes below US$25,000 were nearly 2 decibels louder than neighborhoods with incomes above $100,000 per year. And nationwide, communities with 75 percent black residents had median nighttime noise levels of 46.3 decibels – 4 decibels louder than communities with no black residents. A 10-decibel increase represents a doubling in loudness of a sound, so these are big differences. (2)
I doubt it’s much different in Canada, with cheaper apartments in areas closer to industry and highways, and more expensive houses in quieter neighbourhoods. Casey, James, and Morello-Frosch also write that,
scientists theorize that since evolution programmed the human body to respond to noises as threats, noise exposures activate our natural flight-or-fight response. Noise exposure triggers the release of stress hormones, which can raise our heart rates and blood pressure even during sleep.
They don’t tell us much more about this theory, but I found an interesting example by Spanish researchers. The explanation certainly resonates with me personally, as I cannot experience the same level of deep relaxation in a noisy environment as I do in a quiet space. The Spanish researchers explain in scientific terms, through the functioning of the (activating) sympathetic and (relaxing) parasympathetic nervous systems, why I feel “on edge” if I cannot get away from noise, and why long-term exposure to noise is exhausting (3).
On my walks this summer, I will appreciate the absence of machine noise, allowing me to hear the rustling of falling arbutus leaves, the whirring of hummingbird wings, and the cracking of seed pods splitting open. When September comes and I have to spend more time in the city, I will once again resort to my earplugs and noise-cancelling headphones.
(1) The Weather Guys, “Does Sound Travel Better in Fog?” (January 6, 2013), https://wxguys.ssec.wisc.edu/2013/01/06/does-sound-travel-better-in-fog/
(2) Joan A. Casey, Peter James, and Rachel Morello-Frosch, “Urban Noise Pollution Is Worst in Poor and Minority Neighborhoods and Segregated Cities,” The Conversation (October 5, 2017), https://theconversation.com/urban-noise-pollution-is-worst-in-poor-and-minority-neighborhoods-and-segregated-cities-81888
(3) Alberto Recio, Cristina Linares, José Ramón Banegas, and Julio Díaz, “Road Traffic Noise Effects on Cardiovascular, Respiratory, and Metabolic Health: An Integrative Model of Biological Mechanisms,” Environmental Research 146 (2016): 359-370.