Traffic isn’t noise

The way we conceive of traffic sounds reveals what we think of as worth hearing.

Flowers spew out the exhaust pipe of a car
Jay Richardson

by Jay Richardson

23 March 2022

Imagine you’re at an exhibition. There’s an installation on something like the Rochdale Co-op or trapezoids in postmodernist watercolours—it’s that kind of gallery. You step into a darkened room and hear this.

It sounds like traffic. You can hear an engine running and tell from the tyre sounds the pavement is wet. There’s a high-pitched squeak from brakes and the occasional horn honk. A bass rumble sits behind it, but in the foreground you hear gritty, rattly engine sounds. Muffled thumps from a stereo fade in on your left. Sometimes the sound sources move past at speed and sometimes they’re unpredictably still.

It feels strange to hear the sound of traffic as art, but that’s the point: if you listen closely and for long enough, it can be rich and musical. It can also be distressing and unpleasant, but traffic sounds are not harmful to everyone in and of themselves. The difference between hearing traffic sounds as meaningful components of a negotiable public space and treating them as a monolithic nuisance marks a political difference. It speaks to what we think an ideal street should sound like, what public spaces like streets should contain, who should be heard on the street, and—most of all—who should keep quiet.

Exhibition Road is one of London’s best examples of an unconventional street soundscape. It reveals just how much room there is for experimentation and variation. Following a redesign in 2011, pedestrians, cyclists, and motorists now share a single surface, paved in small square blocks of black and white granite. Traffic makes a loud, bubbly, mid-frequency sound, similar to how it sounds on cobblestones, in contrast with the low-pitched hum of tarmac. There’s enough space for three or even four people to walk side by side, so they tend to talk to each other. The shared pavement model slows drivers, so their vehicles are quieter, which in turn makes talking easier for pedestrians. You can mostly cross the street wherever and whenever you want, so there are no intersections, no crossing signal beeps, not much braking, and almost no idling engines.

Exhibition Road was widely praised for the redesign, winning a Royal Institute of British Architects London Award in 2012. It’s full of potential lessons for acoustic designers, whether or not you actually like the sound, because it diverges in feel and experience from almost every other main street in London.

Unfortunately, it’s also impossible to detect that divergence using the noise abatement engineer’s tool of choice: the sound level meter.

Green Lanes and Exhibition Road would give you almost the same volume reading, even though one might feel much less stressful to experience or live on than the other. In fact, you’re trying to work out how much stress someone will experience from traffic sound, decibels are generally a crude measure and their effects are incredibly difficult to isolate.

You need to distinguish between nighttime sound that affects sleep and daytime sound that doesn’t, except that it does for people who work nights, which means you need to know who those people are and which shifts they work, which they might reasonably not want to tell you. Your volume measurement won’t tell you anything about the pitch, rhythm, timbre, duration, or complexity of the sound, which all influence how people respond to it. Then you need to isolate whatever stress you’re observing from traffic’s other stressful effects: air pollution, vibration, and the social factors that correlate with living in high-traffic areas, including poverty. And even if you control for air pollution, you can’t control for people’s psychological associations between traffic sounds and air pollution. Put another way, if diesel engines spewed out chamomile and rose water and cars didn’t regularly kill people, our emotional responses to traffic sounds might be very different.

Most importantly, you need to study a wide variety of people. The claim that traffic noise is lethal to humans doesn’t stand up if you only study people born in Denmark between the ages of 50 and 64, as two influential studies did in 2012 and 2013. We can’t be confident that traffic noise is a harmful risk factor for obesity in “general populations” by studying only residents of the UK, the Netherlands, and Norway. The way that Europeans hear sound is not necessarily how everyone hears it. In short, none of these studies explains why traffic noise is inherently any more stressful than the sound of the sea.

Academics have long asked how people interact with sound, when and why they find it stressful or otherwise, and what kind of sonic environment they actually do want to live in—including the convenors of the SALVE project at the University of Duisburg-Essen, to take one recent example. Acoustics policy serves people better by engaging with them directly, instead of relying on computer models, compensating for their impersonality with enormous datasets, and falling back on the deeply flawed notion of ‘acoustic quality’.

Politics and inequalities in public spaces are audible if you listen to traffic sounds closely. Here’s a recording from London’s Eaton Square, the most expensive street in England and Wales, with an average house price of £16.9 million.

Taking this recording, I saw more electric taxis than I could shake a microphone at. That means a higher proportion of tyre sounds to engine sounds, so the traffic sounds lighter and softer. The vehicles that do run on petrol or diesel tend to be Mercs and Bentleys with smooth-sounding engines and there are very, very few buses—I saw five during a half-hour walk. You won’t hear anyone pumping drum and bass out of their car speakers, but you will hear more than the average amount of birdsong for a spring evening coming from Belgravia’s mature trees. All the houses are set back from the road, and even then, the pavements are wide enough for you to get some distance from the traffic, so you walk apart from the sound source. No one’s engine is backfiring. No one honks, which is baffling for a place full of taxis. I crossed the street too quickly and almost got run over by a Rolls-Royce—and still didn’t get honked at.

And if Eaton Square is quiet, Belgravia’s smaller side streets and gardens are practically silent. This is central London, SW7, at 6:45pm on a Saturday, and you can hear every bird in every tree within 150 feet. Endless garden walls, tall trees, and hedgerows dampen the neaby traffic, so only a white noise background makes it through. Joggers and dog walkers wander alone with headphones on, looking at the ground. The random, muffled cheer at 2’45” comes from a nearby event in a church, but it lasts about five seconds and quickly dies down to be enveloped again by peaceful, eerie silence.

I came to like the sound of traffic more just by listening back to the recordings. I still find it stressful, but not enough to justify calling it noise. And I’m not alone: just read the comments on 10-hour ‘traffic sounds’ videos marketed for sleep and relaxation, often with millions of views.

Why does this matter? Because definitions of noise speak to what we think belongs in our public soundscapes—or fail to do so and end up implying that everyone should be quiet all the time. The sound scholars Milena Droumeva and Randolph Jordan recently argued, in Sound, Media, Ecology, that treating everything loud and complex as ‘stressful’ or ‘harmful’ often comes from “an attempt to transpose arguably romanticized notions about the natural-ness of nature into fraught social relations,” and “a movement to quiet an increasingly loud, diverse, challenging, technologized world.” It matters because at the other end of a sound source is a person. º



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