Noise is about more than loudness

 kw: book reviews, nonfiction, science, sound, noise, soundscapes

For about ten years I have worked part time at the Delaware Museum of Natural History (renamed in 2022 the Delaware Museum of Nature and Science). My "office" is on the top floor, above an exhibit hall. During the times the museum is open to the public, I constantly hear the sounds of children talking and shouting in the hall below. I happen to like it. Happy sounds are good sounds. On occasion I venture downstairs to wander among the exhibits. There, the sound is much louder, particularly where there is an exciting exhibit in that exhibit hall. The sound is equally happy, but at that volume, it soon gets tiring and I go back upstairs.

I haven't measured the sound level at the museum—I only recently downloaded an SPL (Sound Pressure Level)  app—but I estimate that the loudness at my desk is about 65-70 dba, about as loud as an older washing machine. Down in the hall, it must be 80 dba or more, with peaks in the 90's…there is nothing quite like a surprised child's shriek!

Near a busy highway, the loudness is also in the 70 dba range, but it is definitely not a happy sound, unless you happen to be a tire salesman and the sounds of tires wearing out leads you to anticipate future tire sales. Few of us treasure the noisy clangor of a busy city street. We go where we must, but when we have a choice, we prefer sounds that are more pleasant, and, importantly, less loud.

The coupled measures of loudness and pleasantness are teased apart for us in Clamor: How Noise Took Over the World and How We Can Take it Back by Chris Berdik.

A definition for those needing it: "dba" means "A-weighted decibels". It is a measure of the intensity of sound, with zero set at the threshold of human hearing. "A-weighting" adjusts the sensitivity at different frequencies to match our ears' sensitivity. The scale is logarithmic, so that an increase of 10 dba means a tenfold increase in sound intensity. Most people consider a 10 dba increase to be "twice as loud," because our senses also follow a logarithmic response.

The app I used to measure sounds after I began reading the book is "SPL Meter" by Keuwlsoft. When installed, it arrives uncalibrated, and I could tell it was reading quite high. I don't have a sonic reference, so to reach an approximate calibration I used several well-reported sounds to set the calibration. Now its readings are about 15 dba lower than before and they accord well with reported measurements. I went around during the past week gathering measurements. I'll discuss a few of these below. The reading shown in this image measures the loudness of a particularly low-flying jet aircraft as measured in my front yard.

The book chronicles the very gradual development of public policy regarding noise. The sonic environment has been ignored almost universally, perhaps with the exception of some of those who plan parks and open spaces such as Central Park in New York City. Central Park is big enough to keep the city's traffic sounds at bay, and many sheltered areas are quiet and restful. Even more so, the gentle forest sounds are soothing, quite in contrast to the typically jangly background noise of a city.

The author's aim is not to add another tome to those extolling quietness and denigrating loudness; rather, his interest is the quality of the sounds that envelop us. Many of us greatly enjoy attending concerts, where the louder sounds threaten to damage our ears; this is more so at a rock concert than at an orchestral concert. But, I have attended an outdoor concert of 1812 Overture by Tchaikovsky that used real cannons. There, it was worthwhile to put one's fingers in one's ears whenever the conductor pointed at the cannons! As fun as that was, I don't listen to loud orchestral music all day long. One of my relatives was a rock drummer for a while and has significant hearing loss. I am a folk singer; we don't go for volume, but for lyrics that touch the soul.

Let's consider: what could make the sounds of a city less stressful? Nearly half of Clamor is about that, about the researchers and companies that design soundscapes. The idea of a soundscape is not to just subtract unpleasant sounds, but also to mix in more pleasant sounds.

Here is my own soundscape practice: As I hinted above, jets fly over our house from time to time. Our neighborhood is in line with one of the runways at Philadelphia Airport, and when the wind is right, the landing pattern has jets sweeping in from all directions to a spot about a mile west of our house, then making a descending beeline for the runway. Most of them are still about a mile high when they cross over, and I've recently measured their sound intensity to be 75 dba. Most of the jets are either a Boeing 737 or an Airbus A320. When a larger plane passes over, not only is it intrinsically louder, but it is usually lower, producing the louder sound recorded above. 80 dba is as loud as my lawn mower, heard from 2 meters away (where my ears are during use). Inside the house, where the background sound level is 24 dba (just a bit louder than a whisper), a jet flying over registers 48 dba, except the big ones exceed 52 dba. Sometimes I take an early afternoon nap. Since 40 dba is generally considered loud enough to disturb sleep, I do this: I turn on the clock radio and reduce the volume until I can't understand the words, but the gentle susurrus of human voices is a kind of white noise that helps me "not hear" the jets when they fly over. My nap is better as a result. The Internet is full of suggestions for private soundscapes: little fountains, audio files of forest sound, playlists of gentle string music, etc., etc.

What is a good soundscape for an office? What do you want to be hearing as you work? What, if anything, should be the background sound for a business meeting, particularly for hard negotiations? All these are being studied. Some progress is being made. Several chapters deal with various aspects of such work.

It's very important to understand that people are hugely various. In the realm of felt experience, "diversity" is much more than ethnicity. Not everyone enjoys the sounds of happy children; some people find it excessively annoying. Most people I know enjoy rock music. There are a very few rock musicians and composers whose work I appreciate; I hate most of it. I like classical music, almost exclusively pre-1900; "12-tone" and "atonal" compositions are just meaningless noise to me. I like country and folk music, but mostly for the lyrics. I like the sounds of a babbling brook in a quiet forest, as seen in this picture, taken in a small woods near our house. Many people would find it either annoying or boring. The sound intensity in this woods is as low as 50 dba, which is "quiet" as defined by urban planners.

I did the following measurements this past week:

• 48 dba outside my front door in the daytime. Most of the sound I could hear was road noise from a highway 1/3 mile (~550 m) away.
• 65 dba from the same spot, when my neighbor across the street accidentally set off his car alarm. Fortuitous timing! The sound is designed to be annoying, to get attention. Most of us have learned to tune it out, making car alarms largely useless.
• 65 dba (ranging from 62-74) seated with friends in a restaurant that doesn't play background music. The higher reading was during conversation at our table.
• 50 dba in the forest as noted above, but...
• 60 dba when crows were calling nearby.
• 82 dba, my lawnmower at 1 meter.
• 79 dba, my lawnmower at 2 meters. Note: a difference of -3 dba indicates the intensity was one-half. Power is proportional to the square of intensity, so this follows the inverse square law: -3 dba is one-fourth of the sound power.
• 64 dba is conversation in an otherwise quiet room. Note that we spoke louder in the restaurant setting.

Clamor comes along at the cusp of a revolution in architecture, city planning, and numerous disciplines that have historically ignored sound. The book is not prescriptive; it is reporting on progress as it happens. I hope in just a few years to find that the sonic environment is more and more taken into account everywhere. I am fortunate to live in a quiet suburb. May those living with more noise soon find that the sounds around them are changing to reduce stress rather than enhance it.