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.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.