Engine Noise – Air

music
ambience: airplane (jet) engine, Airplane in Flight

The roar of a jet engine overhead has become an all too familiar sound. Researchers looking for ways to reduce the noise have made a surprising discovery. I’m Jim Metzner, and this is the Pulse of the Planet.

[Jet Engine]

That’s the sound generated by an average commercial jet aircraft engine. Dennis Huff is chief of the acoustics branch at Glenn Research Center.

“What we work on mainly is aircraft noise and what we’re trying to do is work on the components on an aircraft that are generating the noise. The noise levels are usually hard to describe, but if you’re sitting near an airport you could experience levels at around 90-95 decibels. That would be, you know, right around the airport. And that’s enough to interrupt a conversation. It’s a quality of life issue around the airports.”

In trying to pinpoint where and how airplanes generate noise, Dennis Huff and his team have found that much of the sound doesn’t come from the engine itself, but from the air turbulence left in its wake.

“The challenge on the jet noise, is that it’s what we call a distributed noise source. The noise is actually being generated external to the engine in many cases and you have to look at, if you could see the turbulence downstream of the engine and you can think of those as different speakers downstream of the engine. And what we try to do is to change the turbulence characteristics downstream of the engine, which would change the way the jet noise is being produced. And that’s the challenge, that makes it a very interesting problem, because we are trying to do things upstream to change the flow field downstream.”

We’ll hear more about noise-reducing technologies in future programs. Pulse of the Planet is made possible by the National Science Foundation, with additional support from NASA. I’m Jim Metzner.

music

Engine Noise - Air

The roar of the the jet engine overhead has an unexpected source. Hint, it's not the engine!
Air Date:08/21/2006
Scientist:
Transcript:

music
ambience: airplane (jet) engine, Airplane in Flight

The roar of a jet engine overhead has become an all too familiar sound. Researchers looking for ways to reduce the noise have made a surprising discovery. I'm Jim Metzner, and this is the Pulse of the Planet.

[Jet Engine]

That's the sound generated by an average commercial jet aircraft engine. Dennis Huff is chief of the acoustics branch at Glenn Research Center.

"What we work on mainly is aircraft noise and what we're trying to do is work on the components on an aircraft that are generating the noise. The noise levels are usually hard to describe, but if you're sitting near an airport you could experience levels at around 90-95 decibels. That would be, you know, right around the airport. And that's enough to interrupt a conversation. It's a quality of life issue around the airports."

In trying to pinpoint where and how airplanes generate noise, Dennis Huff and his team have found that much of the sound doesn't come from the engine itself, but from the air turbulence left in its wake.

"The challenge on the jet noise, is that it's what we call a distributed noise source. The noise is actually being generated external to the engine in many cases and you have to look at, if you could see the turbulence downstream of the engine and you can think of those as different speakers downstream of the engine. And what we try to do is to change the turbulence characteristics downstream of the engine, which would change the way the jet noise is being produced. And that's the challenge, that makes it a very interesting problem, because we are trying to do things upstream to change the flow field downstream."

We'll hear more about noise-reducing technologies in future programs. Pulse of the Planet is made possible by the National Science Foundation, with additional support from NASA. I'm Jim Metzner.

music