Just Too Loud

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Noise can be controlled to an extent, depending on the source. Some of the biggest sources of ambient noise are highways and roads, but the cause is less honking horns or gunning engines though those play a role than tires hitting pavement. Pliable rubber making contact with asphalt doesn't seem as if it would produce a lot of noise but in fact it does, and in a lot of ways. As any spot on the tire strikes the highway, it hits with the thunk of a little rubber hammer. Also, the patch of tire that's in contact with the ground at any instant the so-called tread block can squeak like a sneaker on a gym floor and pop like a suction cup when it pulls back off the surface. Air pumping through tire grooves makes noise of its own.

The solution, says engineer Bob Bernhard, co-director of Purdue University's Institute for Safe, Quiet and Durable Highways, is to change not the tires but the road surface. "You can make the pavement porous," he says, "which affects the air-pumping mechanism. You can also mix a little rubber in with the asphalt, which changes the road's stiffness." Porous surfaces are already being rolled out in parts of Georgia, Florida and Arizona, as well as in Europe.

Road noise that cannot be eliminated can be muffled. More and more highways are being framed by high walls, additions that do little for the view but an awful lot for the peace and quiet of the people living nearby. The walls reduce noise by either reflecting or absorbing it. This low-tech though pricey fix about $1 million a mile reduces sound levels only as much as 7 db, but given the exponential way noise propagates, that's a lot. "A 10-db reduction may work out to a halving of loudness," says Nicholas Miller, head of Harris Miller Miller & Hanson, a noise-consulting firm in Burlington, Mass.

Airport noise is harder to stifle but not impossible. An airport can determine which of its runways require a plane to fly over the least populated area and use those as its default approaches. Miller's firm recommends that noisy banking on takeoffs and landings occur over water where possible. Other studies suggest that pilots eliminate the stair-step method of descending from flight and instead ease down at a smooth angle to eliminate a lot of noisy throttling.

Local governments have also started to step in. In 2002, New York City launched what it calls Operation Silent Night, a campaign to crack down on noise in 24 high-volume neighborhoods. Police officers with noise meters impose fines from $45 to $25,000--the highest ones going to scofflaw businesses like nightclubs. Noise summonses jumped 20% in the first year, making the city not only quieter but safer too, since some of the noisiest offenders turned out to have outstanding warrants for more serious offenses.

The European Union has been somewhat more aggressive in combatting noise. Calls for explicit limits on noise were rejected by the European Parliament, but compromise legislation does require all member countries to produce color-coded, 3-D noise maps of all major cities, enabling planners to spot the biggest problems at a glance. The maps, which must be completed by 2007, can then be used for computer models to test the noise impact of a new building or street design before construction begins. In a city like Paris, where a single noisy motor scooter in the middle of the night can wake up more than 200,000 people, a little planning can go a long way.

In the U.S., there is still no comparable program. Representative Lowey's bill, now pending in Congress, would provide $20 million a year for noise reduction and reopen the shuttered noise-abatement office. Some appliances are now designed for reduced noise, and a uniform-labeling program could enable consumers to compare decibel levels the same way they compare energy efficiency in a toaster or dishwasher.

Ted Rueter's Noise Free America is pushing a more aggressive approach, filing class actions against makers of boom-car equipment, for example. "The ads that companies run to encourage kids to invest in these things are despicable," he gripes. He hopes that restaurants and other establishments will be required to post noise levels at the door alongside no-smoking, occupancy-limit and alcohol-warning signs.

Such micromanagement of noise may never be entirely possible, but it may be the best of an imperfect array of options. The alternative walling ourselves off behind a thickening barricade of earplugs, triple-glazed windows and white-noise machines may keep down the noise, but it will also deafen us to much of the world, not just the parts we don't want to hear.