Have you noticed that it’s really quiet after it snows? There is a time between snowfall and when the snowplows and snowblowers startup when there is a peaceful silence. These brief respites from noise and busyness are among my favorite times in winter.
As Raymond Knister notes in his poem, snow slows down the rushed and harried whirlwind of life in the city. We allow ourselves a rest from our typical breakneck pace, and there is less outdoor activity as a result; there are fewer cars on the road, and many people are indoors. The fewer number of sound sources contributes to the sense of quiet.
In addition to the slow down of activity, there is another major reason for the quiet after a snowfall: the sound absorption provided by the snow. Freshly fallen snow is very porous and all those nooks and crannies between snowflakes turn some of the sound that hits them into heat. Not a lot of heat, though; you should not plan on melting the snow in your driveway with a giant loudspeaker.
A couple of scientists in England in the late 1930s were interested in how sound absorptive snow is. They had a reverberant chamber at their disposal, the kind of room that is often used to measure the sound absorption of architectural materials like acoustical ceiling tile and fabric-wrapped wall panels. After a snowstorm, they carried a bunch of snow into their test room and measured its sound absorption. As you might expect, indoor tests on snow can be quite challenging, and these scientists wrote: “the measurements were necessarily conducted somewhat hurriedly, and the results…can only be approximate.” Their measurements of a 4-inch snow layer work out to a Noise Reduction Coefficient (NRC) of 0.89, similar to high performing acoustical panels. They measured a few other ground materials including grass, gravel, and sand and found that snow was more absorptive than all of these.
Fresh snow is a lot more absorptive than asphalt, compacted snow, ice, and even frozen grass. So right after it snows, the ground reflects a lot less sound than before the snowstorm. As a result, sound drops off more with distance, making the sounds that reach you quieter.
The next time it snows, take a minute, grab a cup of coffee, and enjoy this brief silent interlude.