Keep It Down Up There!

Tired of ear-piercing aircraft noise? New technologies promise to quiet jet engines

If you live near an airport, you're probably familiar with the Boeing alarm clock--a low-flying jet that roars overhead just as you're about to doze off to sleep. Situate yourself just 300 feet from the tarmac, and the cacophony of a 757 during takeoff can easily hit 120 decibels. That's on par with a rock concert and loud enough to cause pain. In fact, according to the World Health Organization, any sound above 30 decibels can ruin a night's sleep. To make matters worse, world airline traffic is expected to more than double by 2022.

Fortunately, aircraft noise pollution shouldn't do the same, thanks to a host of new technologies designed to silence jet aircraft. Boeing engineers, in partnership with scientists at NASA, Goodrich and General Electric, recently completed flight tests of eight noise-reduction strategies with the ambitious aim of cutting aircraft racket in half by 2007. Here, a rundown of the most promising technologies.

The Engine: General Electric GE90-115B
Quiet Tech: Boeing tested two new technologies on the already quiet GE90-115B: a sound-absorbing liner and serrated edges around the air inlet that smooth airflow.

Power: The GE90-115B is the largest, most powerful jet engine. A bigger fan enables the blades to rotate more slowly, reducing noise and increasing efficiency.

Takeoff Date: While the modified GE90-115B won't make commercial flights, its quiet technology will appear on the Boeing 787 in 2008.

Hush Factor: The new tech reduces the buzzsaw noise heard in the front of the plane, which is the result of shockwaves created when fan blades rotate at full speed.

The Engine: Rolls Royce Trent 900

Quiet Tech: This engine features curved, aerodynamic engine blades that reduce noise by smoothing out airflow.

Power: Quiet doesn't mean less powerful--Rolls Royce's biggest engine, the Trent 900 emits up to 80,000 pounds of thrust.

Takeoff Date: The engine debuted on an Airbus A340 test plane in May 2004. It's now flying as part of the Airbus A380 test program.

Hush Factor: Thanks to the new technology, the engine is four decibels quieter than Rolls Royce's current engines.

The Engine: The GE Genx

Quiet Tech: The GEnx's longer fan blades enable more air to pass around the turbine than through it, generating more thrust but much less noise.

Power: Engine thrust equals 55,000 to 72,000 pounds, depending on the model. The GEnx features the highest air-bypass ratio of any jet aircraft.ngine.

Takeoff Date: Engine testing begins in 2006, with adoption on the Boeing 787 by 2008 and on the newly announced 747-8 later.

Hush Factor: The most impressive quiet jet engine to date, it will be 13 decibels

quieter than the previous version.