While some scientists focused on making buildings quieter, other researchers were seeking ways to reduce the amount of noise in the outside environment. One group of scientists, at the Brookhaven National Laboratory in Brookhaven, New York, was developing a new version of what is perhaps the premier emblem of excessive urban noise: the jackhammer. They called their new, quieter pavement-buster the Rapid Cutter of Concrete, or “Raptor.”
A conventional jackhammer, which bombards peoples' eardrums with sound levels of about 120 decibels, uses compressed air to drive a steel cutting head relentlessly against a hard surface, such as concrete, until it crumbles. The Raptor uses bursts of compressed air to propel steel nails into pavement at very high speed to break it apart. Although the sound of each shot is about as loud as a conventional jackhammer, the Raptor does not operate continuously, firing a nail about every 6 to 10 seconds. In 2001, the Brookhaven engineers had plans to make the tool even kinder to people's ears by outfitting it with a silencing device similar to those often used on firearms. They expected that this modification would reduce the Raptor's noise level to only about 85 decibels.
(Source: How stuff works?)