TACKLING1 CITY NOISE
Anyone who has spent a night in a big city knows how hard it can be to fall asleep there. Car horns, motorbikes, sirens2 and building work go on almost around the clock. Health experts now see this noise as a real danger, not just an annoyance. Years of living with loud traffic can lead to poor sleep and high levels of stress, and can also raise the risk of heart disease. Experts also warn that the situation is going to get worse, since urban populations are growing and there are more cars on the roads every year.(lines 1–6)
The traditional answer to traffic noise is the noise barrier3, a tall wall built beside a highway. Such walls protect the houses right behind them, but there is no space for them in most city streets. Besides, much of the noise comes from just a few vehicles. "A single motorbike with a loud exhaust4 can be as noisy as fifty cars," explains acoustic engineer Daniel Reyes. Buildings make matters worse. Most are made of glass, concrete and stone, and these hard materials cannot absorb5 sound. "The sound is reflected6 from one building to the next instead," Reyes says, "so a street of tall buildings can be much louder than an open road."(lines 7–13)
Since walls cannot solve the problem, many cities now try to make the vehicles themselves quieter. Old diesel buses and garbage trucks are being replaced by electric models, whose engines make almost no sound at low speeds. As a result, whole neighborhoods have become calmer. Another step is a lower speed limit at night, because slower cars produce less noise. "Of course, a lower limit means a longer trip home, and drivers are not happy about that," Reyes admits. "Still, most of them are city residents themselves. They realize that quieter nights will help them, too – they will sleep better and be healthier."(lines 14–20)
Technology is helping cities find the noisiest vehicles. Paris, for example, has tested "noise radars" – cameras with microphones that pick out an unusually loud vehicle and photograph its number plate, so that the owner can be fined7. Elsewhere, the police reach the same goal without cameras: officers stop vehicles that sound too loud and measure the noise at the roadside. "Drivers who break noise rules often drive dangerously as well," says Reyes, "so catching these offenders8 makes the roads safer. And quieter streets bring neighborhoods back to life. People open their windows, walk more and chat with their neighbors."(lines 21–27)