Why Every City Sounds Different: A Field Guide to Urban Acoustics

Tomas Reuter claps once, very hard, in the middle of a courtyard off Choriner Strasse in Berlin at ten past six in the morning, and then stands completely still with a stopwatch he is not looking at. A window opens on the third floor. Nobody says anything. The window closes.

"Two and a bit," he says. "I will measure it properly, but it is two and a bit."

Reuter is an acoustician with Ostend Acoustics in Rotterdam, and most of his paid work involves stopping buildings from annoying their neighbours. The unpaid work, which he has been doing for eleven years in whatever city a job sends him to, is a map of how streets behave as rooms. He has 3,800 measurements in it. Berlin is not the most reverberant city he has recorded, but it is the one that surprises people most, because it is the one they think they know.

The clap test

The formal measurement is reverberation time: how long it takes a sound to fall by sixty decibels after the source stops. Indoors it is the difference between a bathroom and a bedroom. Outdoors, where there is no ceiling, the number should in theory be tiny, and often is not, because a European street with buildings of equal height on both sides is functionally a long room with the lid off.

Reuter's method is unglamorous. A balloon or a hand clap, a small omnidirectional microphone on a stand at 1.5 metres, three positions per street, at an hour when the traffic is thin enough to leave a decay visible above the noise floor. He does not use a starter pistol any more. "You get one measurement and then a conversation with the police," he says.

The variables that matter turn out to be boringly physical. Street width against building height. Whether the facade is flat render, rough brick, glass, or broken up with balconies and shutters. Ground surface. Trees. And, decisively, how much noise the city makes at rest, because a two-second tail that sits below the ambient level might as well not exist.

A city is not a room, but it behaves like one, and nobody designed the room. Every acoustic property a street has is an accident of what people could afford to build with.

Why Berlin rings and Lagos does not

Reuter's Berlin courtyard measured 2.4 seconds at 500 hertz: flat stucco on all four sides, stone underfoot, a height-to-width ratio close to one to one, and almost no soft material anywhere. Sound has nowhere to go but back and forth.

A street of comparable width in Lagos, measured by Reuter on a job in 2023, came in at 0.9 seconds, and he considers even that generous. Open frontage, unrendered blockwork, corrugated roofing that absorbs and rattles rather than reflecting cleanly, ground that is rarely hard the whole way across, and vegetation in the gaps.

Adaeze Nwosu, a field recordist who has logged around 1,400 hours in Lagos and contributes to our Field Recording Atlas, thinks the physics is only half of it. "The tail exists. It has nowhere to be heard," she says. "My quietest measurement on Ikorodu Road, three in the morning, is 62 decibels. In Berlin at three in the morning Tomas is recording rooms at 32. He is measuring architecture. I am measuring architecture plus everybody in it."

Then there is rail. A tram running jointed track at 40 kilometres an hour lays down a pulse roughly every 1.6 seconds, and it is loudest in exactly the low-mid band a bass guitar occupies. Reuter has measured streets in Budapest, Prague and Leipzig where the tram is effectively a metronome that every rehearsal room on the street has been playing along with for a century.

Five cities, five signatures

A crude summary of a complicated subject, with all the caveats a two-line description deserves.

• Berlin. Flat render, stone courtyards, near one-to-one street canyons: a long grey decay that flatters anything slow and turns anything fast to porridge.
• Lagos. Open frontage, soft ground, a noise floor that never really drops: no tail survives, so the music is built out of transients and top end.
• Seoul. Glass, polished stone and tiled interiors stacked vertically: hard early reflections and a high end that seems to arrive twice, as anyone who has stood in that bathhouse on a patch night can confirm.
• Manchester. Brick, low ceilings, wet air: a short warm decay that hides mistakes below 200 hertz and exposes every one above it.
• Tbilisi. Basalt, wooden balconies and streets on a slope: reflections that come back from above you rather than beside you.

Sao Paulo belongs on the list and would need its own entry, because the warehouse districts and the tower canyons behave like two different cities that happen to share a postcode.

The city gets into the record

None of this stays outside. It gets into the music, mostly through rehearsal rooms, which are the cheapest available spaces and therefore inherit the acoustics of whatever the city could not sell.

Elif Duran, who scores documentaries about abandoned buildings and spends more time listening to empty rooms than most people spend listening to music, describes it as an argument you can either have or lose. "Every space I score already has a piece of music in it," she told us. "If I write something with a lot of information in the low mids and put it in a hall with a three-second tail, I have not written a piece, I have written a fog. Mostly the job is finding out what the room already wants to do."

You can hear the same logic in reverse in records built entirely from a location's own acoustic behaviour, of which the best recent example is the dying-mall album, where a corridor's flutter echo is doing more compositional work than anything a musician plays. Reuter, who has been sent it by three separate people, says the escalator hum on the second track is almost certainly a resonance of the atrium rather than the machine.

He offers one piece of advice for anybody who wants to start hearing this. Walk a street you know at five in the morning and clap. Then walk it at five in the afternoon and clap again. The building has not changed. Everything else has, and the difference is the reason your favourite band from that city sounds the way it does.