Traffic isn’t noise

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

Jay Richardson

by Jay Richardson
Wednesday 23rd 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 that the pavement is wet. There’s a high-pitched squeak from brakes, 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, sometimes they’re still: the recording is dynamic and unpredictable.

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 public space—a space to be negotiated, in full view (earshot?) of everyone’s lives—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, and—most of all—who should keep quiet.

An exhaust pipe spouting red sprigs and flowers

Exhibition Road is one of London’s best examples of an unconventional street soundscape, one that 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 is 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 easily cross the street at will, 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 the Institute of Civil Engineers’ Community 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.

The two streets in these recordings would give you almost the same volume reading, even though one might feel much less stressful to experience or live on than the other. If you’re trying to work out how much stress someone will experience from sound, decibels alone are 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. Even if you manage to figure out the daytime-nighttime problem, your volume measurement won’t tell you anything about the pitch, rhythm, timbre, duration, or complexity of the sound. Then you need to adjust for air pollution, vibration, and the social factors that correlate with living in high-traffic areas, including poverty. And then, even if you control for air pollution, you can’t control for the stress response that people who associate traffic sounds with polluted air might feel when they hear traffic. 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. As should be abundantly clear from the art of music, the way that Europeans hear sound is not always how everyone everywhere else hears it. In short, none of these studies explains why traffic noise is any more stressful than the sound of the sea.

A modern-looking car exhaust spouting red, orange, and pink flower petals

There are plenty of humanities disciplines that can tell us 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—questions that the SALVE project at the University of Duisburg-Essen has been asking since 2018. 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 falsely objective notion of ‘acoustic quality’.

The politics and inequalities in public spaces are audible if you listen to traffic sounds closely. Here’s a recording from London’s Belgravia district of 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. Those 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 & 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 comparatively apart from the sound source. No one’s engine is backfiring. No one honks, which is pretty remarkable 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 with about 150 feet. The sound of nearby traffic is dampened by endless garden walls, tall trees and hedgerows, so only a background of white noise makes it through. And yet, unlike on Exhibition Road, the lack of traffic doesn’t mean that people are talking to each other. The joggers and dog walkers are solitary and go about 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 silence. It is peaceful, but I found it almost eerily so.

A lorry and car on a dual carriageway, both spouting flowers from their exhausts

While taking these recordings, I came to like the sound of traffic more. I still find it stressful, but not enough to justify calling it “noise”. I’m not alone: just read the comments sections on 10-hour traffic sound YouTube videos marketed for sleep and relaxation, often with millions of views.

Why does this matter? Because it implies a vision of what the soundscape should be like—or fails to do so and just ends up implying that everyone should be quiet all the time. Sound scholars have argued over this for decades: as Milena Droumeva and Randolph Jordan recently wrote in Sound, Media, Ecology, treating everything loud and complex as ‘stressful’ or ‘harmful’ sound risks “an attempt to transpose arguably romanticized notions about the natural-ness of nature into fraught social relations … 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.