The Science of Quieter Cities
Cities sound like cars honking and sirens blaring and trains rumbling underfoot. They sound like the couple fighting on the other side of your kitchen wall and the garbage truck backing up out your window. They sound, generally, chaotic and constantly on. And if you live in one long enough, all of this noise starts to blend into a kind of neutral hum, the urban equivalent of crickets chirping.
For unaccustomed ears, though, the sound of the city can be a big, if invisible, barrier to actually moving to one.
“The challenge is to prove to people that living close is living well,” says Thomas Jones, the dean of Cal Poly’s College of Architecture and Environmental Design. “Noise is a huge piece of that. When people talk about cities, they say ‘they’re dirty, they’re ugly, they’re noisy.’ And many people are choosing single-family homes even now because they’ve had terrible living experiences in multi-family housing where they could hear everything everybody upstairs and next to them was doing.”
This leads, Jones laments, to a serious prejudice against city living. And that impression stands at odds with demographic projections that warn more young people want to move into cities, more baby-boomers want to downsize there, more demand for apartments is coming, and more people want to relocate in close proximity to prizes like metro stops.
If all of this is accurate, and even more people will soon be living on top of and right next to each other – while sharing sidewalks, roads and public plazas – could we design better places where we could all live together without hearing quite so much of each other? And just what would that sound like?
These aren’t questions only for apartment-dwellers. Obnoxious city noise comes from all around us, moving between buildings and through windows and across congested roads. If we don’t tame it, Jones worries, people will never willingly rearrange themselves into the denser living patterns environmentalists say we need.
“People think, ‘Oh we need electricity from solar panels, we need x-y-z system, we need to use less water,” Jones says. “But we absolutely have to make living in denser urban environments pleasant to the senses, or we’ll lose the environmental battle.”
Maybe it’s time to start looking at townhouses and bus shelters with the same acoustic care engineers have long given to concert halls and schools. In doing so, it’s possible we could make the city sound not just quieter – but, in a very real way, more pleasant.
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The global engineering firm Arup (they did the structural design for the Sydney Opera House) has built sound labs in Los Angeles, San Francisco, and New York City, where they’re doing some unbelievable things with urban noise. In the past, an acoustic engineer could tell you, “this sound is about as loud as a major highway when you’re standing 20 feet away from it.” Or: “This room is quiet enough for two people sitting across a table to carry on a conversation.”
In the sound lab, though, Arup engineers can demonstrate and manipulate the noise level, source and character of any sound, in any environment. They can record the blare of a passing train – in real life – and play back in the lab what it would sound like from within your apartment, with your windows closed.
“It’s sort of magical,” says Nick Antonio, Arup’s Acoustics Group leader in Los Angeles.
Arup doesn’t simply want to figure out how to make things quieter. There are plenty of sounds that people like: birds singing, children playing, trees rustling at night. The real challenge is to baffle the noises people don’t want to hear while amplifying the ones they do. With this conundrum comes myriad others: How do you keep noise out of an apartment while letting fresh air in? How do you adjust for the aural quirks of the human ear at different decibel levels?
At a given sound level, for instance, people generally get more upset about helicopters than we do fixed-wing aircraft. And we tend to get more upset – at the same decibel level – about fixed-wing aircraft than auto traffic. We like trains, though, and we’d typically prefer the sound of one to the equivalent in passing cars.
“So we can’t just mechanistically look at a number,” Antonio says, “and say, ‘this is acceptable or this is not.’”
Take those miserable traffic-calming speed bumps. One of the great ironies behind them is that they generate as much noise when vehicles bash into them as they reduce in the sound of speeding cars. And if you’re sitting inside your living room near one, you’re more likely to be disturbed by the sudden thwack of a scraping muffler than by the whirl of passing cars that fades into your background city soundtrack (this is one of the problems Arup is working on: designing quieter road surfaces, not quieter speed bumps).
“This is difficult to describe because effectively what we’re looking at is a sense here, and arguably it’s your second most important sense,” Antonio says. “And it’s your whole environment from that point of view. You are continually swimming through this sea of sound for your entire life. And you have no equivalent to an eyelid in sound terms. You have no ear-lid.”
(You have earplugs, you say? Antonio counters that they really produce a slightly different sound, not the absence of it.)
Sight, on the other hand, is a linear thing. Look up from your computer screen, and your eyes can take in as much of the environment as your turning head can handle. But sound comes from 360 degrees around us – and it comes from places we cannot see.
“Once we’re into this mindset, we start thinking about the way that an acoustic horizon is different from a visual horizon,” Antonio says. “An acoustic horizon in your apartment goes past the visual horizon – the walls, the curtains – because your acoustic horizon stretches past that window to the cars beyond. It might reach to a new couple next door and their newborn baby. It could reach to the guy above you and his heavy-footed shoes.”
The acoustic horizon presents us with this inherent tension in cities. You probably wouldn’t move to one if you didn’t want to be connected to other people. There would be little point to cities if we were all sitting in our own hermetically sealed boxes. But how do we keep that connection without being disturbed by it?
“I suspect this is true of most design: Space and the use of spaces is effectively evolutionary,” Antonio says. “Where people have issues associated with something, somebody will do something about it.”
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Inside buildings themselves, older, pre-war apartments are generally quieter, as are those that have been built in the last decade. The problematic stuff was really constructed in between.
“The idea that you regulate acoustics only evolved after we realized we’d built a huge number of buildings which basically didn’t work from acoustical privacy,” Jones says. “There wasn’t an advocacy group out there that said ‘we’re low income, we’re renters, and we don’t want to live with this stuff.’”
Federal regulation, and then city building codes, didn’t start regulating for noise until the 1970s. Today, the Uniform Building Code provides minimum standards for noise levels between units of multi-family dwellings, although they’re lower than people who can afford to pay for solitude would generally put up with. America has some of the poorest standards in the world, Antonio says. Scandinavia has some of the best. But some of the difference is cultural: Those strict northern European standards tend to relax heading south into the more proudly cacophonous Mediterranean. (Our noisy American cities also have nothing on East Asia, which has millions of scooters all riding around without the benefit of mufflers.)
In America, creating quieter places will be a matter of embracing both earlier building techniques and modern technology. Architect Kathy Dorgan lived for years in a townhouse built in 1888 and recalls hearing her next-door neighbors just once, in the midst of some construction.
“If we could do it in 1888,” she says, “we certainly could do it today.”
Some of the solution is just good design (and good materials: brownstone is great at quashing sound). Windows shouldn’t be aligned directly across from each other. Buildings that abut noisy roads would do better to put closets and bathrooms facing them rather than living spaces. Greenery – a pretty old-school material – also helps absorb sound, whether from plants on your porch or trees lining your street. This is also part of the reason why Central Park in New York City sounds like such a respite.
More recent advancements – new framing techniques, triple-glazing on windows, wall vents that circulate fresh air while muffling sound – also ensure that buildings that will go up in the coming years will sound nothing like those from the 1960s.
“You could be living next to a freeway,” says Oakland-based architect Mike Pyatok, “and all you have is a light show.”
Many of these improvements have been driven by market pressure. As the prime land in cities disappears, denser developments have been going up on less and less desirable land. Formerly industrial neighborhoods are converting into high-end residential ones, but those sites are still located next to rail lines and highways. Builders there recognize that wealthy residents won’t pay for noise. The trick will be extending advancements born from this market pressure to lower-income neighborhoods and existing retrofits.
Outside of buildings, some of the noisiest hallmarks of cities have steadily been improving. Pyatok recalls living in a Brooklyn apartment half a block from a stretch of the elevated Myrtle Avenue subway line that no longer exists. Anyone who has lived near an elevated train knows the way its regular arrival rearranges every-day life: “If you’re watching television,” Pyatok laughs, “you learn to read lips.”
“Most of the more horrendous sounds have been done away with,” he says, “when they can be done away with.”
Airports are a big exception. But between those big-ticket noise polluters, and the improved party walls between our interior spaces, some of the most intriguing solutions will touch on the interplay of city sound between the outdoors and the inside, when we have our windows wide open. This is when you want to hear the children in a nearby playground, but not the passing truck.
"If you’re just designing that building, there’s almost nothing you can do,” Antonio says. “When we have the ability to provide input into the planning stage, and the holistic design, when we’re not just literally plunking a building into a plan with no regard to the acoustic environment, then we can actually start looking at reducing noise and providing a much more pleasant sort of space.”
This is when engineers can think about masking traffic with water features, filtering it through living green screens or paving sidewalks alongside roads to produce their own soundscapes.
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The whole idea here is that we don’t have to accept cities as noisy places, that apartments can be private and roads can be calmer and whole neighborhoods can sound, if not like the countryside, then something more humane.
“To just accept the status quo is turning our back on innovation and design,” Antonio says, “and why we’re doing this in the first place.”
Cities have soundmarks, like landmarks. In San Francisco, it’s the sound of a trolley bell. In New Orleans, it may be the muffled trumpet of a nearby jazz bar. If we could tune up these sounds and tune down the unwanted ones, it’s intriguing to think about what the city of the future would sound like.
The main wash of noise in cities today comes primarily from road traffic, HVAC units and aircraft. The Federal Aviation Administration has been working on this last one, and HVAC units are getting more sophisticated, too.
“The really exciting one to me is what’s happening in road traffic.” Antonio says.
There are more and more hybrids on the road every year, and they present an intriguing opportunity for acoustic engineers. Hybrids and electric cars are practically silent. In fact, they’re so silent it’s becoming a safety problem. Eventually, designers will have to impose some kind of sound on these vehicles, a prospect that delights Antonio and other acoustic engineers starting to debate this question.
“What we effectively have at the moment is a blank canvas,” he says.
Once we blot out your neighbor’s high heels and your building’s HVAC, once we put triple-glazing on your windows and quieter paving on your street, the sound of the city is largely the sound of cars. And in the future we could make cars sound like anything we want. How about a fleet of vehicles driving around town, singing just like birds?