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Musing on Mowing, part 1:
The Roar of Summer Lawns

In my garden, I try to create an environment of beauty and harmony, to nourish peace and joy in everyone who looks at it. But every nice day, irritating vibrations invade — from neighborhood lawn mowers.

The danger of toxic noise is not widely recognized. As a result, hearing loss, which is cumulative, is common in the elderly in our culture, as well as increasing at younger ages. Regulations on noise pollution are probably not strict enough, according to experts. In addition they are seldom enforced, and have gaping loopholes, for example the exception Massachusetts gives to "domestic equipment such as lawn mowers and power saws between the hours of 7:00 A.M. and 9:00 P.M."

The accepted method of evaluating danger is its loudness, measured in decibels, compared to exposure time. But new research indicates many additional factors need to be considered, for example the "impulsiveness" of the sound: when it's composed of short impulses of relatively high energy content, which stand out against the moments between impulses. The sound of a lawn mower is one of the worst offenders in this category, as is a jackhammer.

Even relatively low decibel levels of noise cause potentially harmful changes in heart rate, respiration rate, muscular activity, hormone secretion, digestive activity, condition of small blood vessels, fetal development, and mental health. "Calling noise a nuisance is like calling smog an inconvenience," says former US Surgeon General William H. Stewart; "Noise must be considered a hazard to the health of people everywhere."

What are humans doing by making our neighborhoods so noisy? Human-made noise disrupts birds' communication, feeding, resting, and nesting — driving them away, or increasing mortality. Many other species of animals and insects have shown problems with our noise.

Plants respond to sound, too. In the early 50s, Dr. T.C. Singh, head of the department of botany at Annamalai University, found that frequencies between 100 and 600 cycles per second produced strong beneficial effects in a large number of plants, including common asters, petunias, cosmos, onions, radishes, and sweet potatoes.

In 1973, concert organist and mezzo soprano Dorothy Retallack reported studies she conducted at Temple Buell College in Denver. When she played steel drums to create percussive sounds, the plants leaned away. I'll bet if you tested how plants grow when subjected to the sound of a power mower, they'd do much worse.

© Copyright 2003 Catherine Holmes Clark


Published in the six Nashoba Publishing papers on Friday, 11 July 2003

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For more information
  • What'd you say?, by Linda Kulman: "Congress established the Environmental Protection Agency's Office of Noise Abatement and Control in 1972 to develop noise-emissions standards for everything from railroad equipment to lawn mowers. It lost its funding amid the antiregulatory fervor of the Reagan era. Once the federal government pulled out, cash-strapped municipal and state governments tended to sidestep it, too."
  • Stop the Noise: An Investigation of Sound Levels in Elementary School, "The louder the sound, the shorter the time it takes to damage a person's hearing. Average conversations are about 60 dB, alarm clocks and heavy traffic are about 80 dB, and discos or rock concerts are about 115 decibels. You can listen to 90 decibels for 8 hours a day before you begin to lose hearing, but if you listen to 115 decibels, it only takes 15 minutes before your hearing is damaged."
  • Massachusetts Noise Laws
  • The Path to Quiet: Don't Just Say, "No" to Noise - Say "Yes" to Quiet, by Nancy B. Nadler, M.E.D., M.A.— from Hearing Rehabilitation Quarterly [documents Stewart quote]
  • Often the only factor attended to is the level of noise. Here are some pages identifying dB of common sounds:
    • Everyday Noise List — various sounds, their decibel levels, and the recommended limit for exposure to each
    • Noise Pollution — a different list, from the Ecological Living - Resource Center for Ecological and Sustainable Living: has more ordinary sounds, and no "recommended limits"
    • Health & Noise (Siemens Audiology Group) — simple dB scale is illustrated; page also includes a general overview of health consequences of noise.
  • Damage-Risk Criteria, from the Handbook for Acoustic Ecology, edited by Barry Truax, (second edition, 1999; originally published by the World Soundscape Project, Simon Fraser University, and ARC Publications, 1978). Information on impact ("impulsive") sound, an additional factor of importance.
  • Low-Level Noise is an Insidious Stressor: "Not just loud or sudden noises provoke a stress response." Yet another factor. On the site of The Franklin Institute Online.
  • The classic source for descriptions of experiments on perception in plants is The Secret Life of Plants, by Peter Tompkins and Christopher Bird. (HarperCollins, 1989). These pages give a little information from there:
  • Piccolo Peril, by Stephen Strauss, Science reporter, from the Toronto Globe and Mail, May 18, 1996. "While modern mythology has demonized rock 'n' roll as the great deafener, research suggests that symphony orchestra players risk more hearing problems than their heavily amplified musical brethren."