When New York Mayor Michael Bloomberg began a much-publicized crusade against noise, he made a bold, if counterintuitive, proposition: A big city, he said, doesn't by nature have to be obnoxiously loud.

Five years later, no one would confuse Manhattan with a library reading room. But Bloomberg's thinking did produce a noise code that is now a national model. It even produced a quieter jackhammer, simply by asking: Does this thing really have to be so ridiculously loud?

I certainly would have assumed it does. After all, a jackhammer's job is to blast through concrete and asphalt. But it turns out that much of the noise a jackhammer unleashes comes from the machine itself, not from the chisel pounding away at the pavement. First, there's the roar of compressed air escaping the unit. And inside, there's a fast-moving piston that smacks into a metal striker at a rate of about 1,800 times per minute. Each time they collide, it's like smashing a small gong.

When city officials set out to write the noise code, they suspected much of the problem with jackhammers could be solved by putting some kind of jacket on them. Trouble was, such a product did not actually exist. A utility executive who was helping the city develop the code approached a few manufacturers about inventing a jacket. None wanted to do it. Finally, an equipment supplier on Long Island agreed to give it a try. The result was a muffler made from a neoprene-like material that wraps around the jackhammer shaft and secures with Velcro. It reduces noise from a typical jackhammer by about nine decibels. To the human ear, that represents about a one-half reduction in perceived loudness. "The benefit is less to the operator of the jackhammer," says Robert Aicher, president of Zo-Air, the company that developed the jacket. "But to a passerby, the reduction is substantial."

Since the code went into effect in 2007, utilities have bought several dozen of the jackets for when they dig into streets to fix wires and pipes. The code also requires that construction crews use "the quietest jackhammer suitable to perform" a given job, and stipulates that smaller, quieter jackhammers be used when pulling out the big guns isn't absolutely necessary. "A lot of people throw up their hands and say, "Well, jackhammers are just a noisy thing,'" says Eric Zwerling, director of the Noise Technical Asssistance Center at Rutgers University in New Jersey. "The only time anything gets done is when government tries to push the market along to come up with creative solutions."