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Noisy Civilization

November 16, 2020

City-dwellers who retreat to the suburbs envision an existence away from ubiquitous sirens and loud traffic noise that assault their tranquility at all times of the day. However, they're disappointed when they discover that the city noise sources have been replaced by similarly annoying lawn mowers, leaf blowers, and snow blowers. Along with these acoustic noise sources come the increased noise-to-signal ratio that limits reception of their former favorite broadcast radio and television stations. We live in a noisy civilization.

You can do an A-B test of civilization noise by retreating to the wilderness on vacation. Fortunately, Tikalon's Northern New Jersey location is less than an hour's travel from some reasonably secluded venues, and a few hour's travel to some real wilderness in New York State. As they say, there can be too much of a good thing, and that includes silence. There's a cautionary tale about an avid reader who had a soundproof reading room constructed in her house so noise wouldn't distract from her reading. After a few minutes in the room, she would invariably fall asleep.

One strange noise source is "The Hum," a persistent low-frequency humming/rumbling noise reported by some people. The most famous of these hums is the "Taos Hum" of Taos, New Mexico. Observers of the Taos Hum reported hearing the noise between 32-80 Hz in frequency, amplitude modulated from 0.5-2 Hz. A New Zealand researcher, Tom Moir, a computer engineer then at Massey University, recorded a New Zealand hum at 56 hertz.[1]

Frequency of occurrence of the word 'Hum' from 1940-2019

Frequency of occurrence of the word, "Hum," from 1940-2019. (Via Google's NGgramViewer.)

Although heavy machinery is a likely source for this noise, few of the reported hums have been traced to any such source. One noise source was definitely identified with a large pump, and a 35 Hz hum in Windsor, Ontario, Canada, ceased when a steel plant there closed in April of this year.[2] Large electrical distribution power transformers have also been cited as a possible source, since transformer core materials will vibrate with the electric current. Another culprit is the vast network of underground pipelines.

Just as the events of September 11, 2001, gave scientists in the United States the opportunity to examine the reduction in diurnal temperature caused by aircraft contrails,[3] the worldwide economic slowdown caused by the COVID-19 pandemic and its resultant worldwide quieting has given another research opportunity. Biologists and mathematicians from the University of Tennessee (Knoxville, Tennessee), California Polytechnic State University (San Luis Obispo, California), Texas A&M University–San Antonio (San Antonio, Texas), and George Mason University (Fairfax, Virginia) have recently published a study that found that one example of birdsong improved in this quiet environment.[4-5]

The specific species studied was the white-crowned sparrow (Zonotrichia leucophrys), which has a standard tune that starts with a few whistles, and ends with a series of complex trills.[5] Previous research showed that sparrows sing at a louder amplitude in a noisy environment, straining to be heard, and this resulted in a lower-quality song.[5] There was an expectation that the birdsong would improve during the pandemic's shelter-at-home mandates and economic slowdown.[4-5]

Zonotrichia leucophrys (photo by Mike Baird)

A white-crowned sparrow (Zonotrichia leucophrys).

(Wikimedia Commons image by Mike Baird, Morro Bay, California)

Because of the pandemic, vehicle traffic in the studied areas of San Francisco and Contra Costa County, California, were reduced to the level of the mid-1950s.[4] The study team expected that this quieting would affect the sparrows' song, but they were surprised by how much.[5] Says lead author of the study, Elizabeth Derryberry, an associate professor at the University of Tennessee, Knoxville, "The songs didn’t change as much as we predicted - they changed even more... It highlights just how big of an effect noise pollution has."[5]

The birds reacted to their newer, quieter, environment by producing higher quality songs at lower amplitudes.[4] All this is important to male birds, who use their songs to find matess and defend their territory.[5] In the quieter environment, the songs of urban birds travelled about twice as far.[4-5] Bird calls in the rural setting of nearby Marin County were essentially unchanged by the pandemic.[4-5] The study demonstrated that an the birds have an inherent resilience to noise pollution, and they can adapt rapidly in response to favorable conditions.[4]

There's no data about the reaction to pandemic quieting by bees, but there has been a study about how the Earth, as a whole, reacted. A global quieting of high-frequency seismic noise was detected by a huge international team from 66 research institutions.[6-7] This study, led by Thomas Lecocq of the Royal Observatory of Belgium (Brussels, Belgium), is published as an open access paper in a recent issue of Science.[6]

Human activity creates high-frequency seismic waves that are detected as a nearly continuous signal, especially on seismometers in urban areas.[6] Not surprisingly, these signals are typically stronger during the day than at night, weaker on weekends than weekdays, and weaker at the Christmas and New Year's holidays where they are celebrated.[6] Mitigation actions to limit the coronavirus (COVID-19) pandemic resulted in a month's long reduction in seismic noise of up to 50%.[6] The quieting of seismicity began in China in late January 2020, followed by Italy, the rest of Europe, and the rest of the world in March to April 2020.[6]

Temporal changes in seismicity from COVID-19 lockdown

Temporal changes in global daily median high frequency seismicity as reported by the 185 stations that observed lockdown effects. Percentage changes are expressed relative to a prelockdown baseline. The weekday-weekend difference, the COVID-19 pandemic quieting, and the usual year-end holiday slowdown can be seen. (Created using Inkscape from data in Fig. 4a of Ref. 6.[6] Click for larger image.)


  1. Mysterious humming driving Aucklanders 'bonkers', New Zealand Herald, October 27, 2006.
  2. Stephen Hutcheon, "Mystery humming sound captured," The Sydney Morning Herald, November 17, 2006.
  3. David J. Travis, Andrew M. Carleton, and Ryan G. Lauritsen, "Contrails reduce daily temperature range," Nature, vol. 418, no. 6898 (August 8, 2002), p. 601, https://doi.org/10.1038/418601a.
  4. Elizabeth P. Derryberry, Jennifer N. Phillips, Graham E. Derryberry, Michael J. Blum, and David Luther, "Singing in a silent spring: Birds respond to a half-century soundscape reversion during the COVID-19 shutdown," Science (September 24, 2020, Article eabd5777, DOI: 10.1126/science.abd5777. This is an open access article with a PDF file here.
  5. Carrie Arnold, "When the pandemic quieted San Francisco, these birds could hear each other sing," National Geographic, September 24, 2020.
  6. Thomas Lecocq, et al., "Global quieting of high-frequency seismic noise due to COVID-19 pandemic lockdown measures," Science, vol. 369, no. 6509 (September 11, 2020), pp. 1338-1343, DOI: 10.1126/science.abd2438. This is an open access article with a PDF file here.
  7. Marine A. Denolle and Tarje Nissen-Meyer, "Perspective - Seismology, Quiet Anthropocene, quiet Earth," Science, vol. 369, no. 6509 (September 11, 2020), pp. 1299-1300, DOI: 10.1126/science.abd8358.

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