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NASA Connect segment featuring a panel of two experts from NASA that answer students' questions by phone and email. The questions pertain to aircraft and noise reduction.
All right, welcome to the NASA Connect studio.
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Now joining me in the studio are Rich Silcox, a senior research scientist, and we're also
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now joined by Dennis Huff from NASA Glenn Research Center in Cleveland, Ohio.
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But before we talk to our researchers, let's give you a chance to do some analyzing using
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the data from the experiment you just saw.
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After this segment, our two researchers will be answering your email questions and taking
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questions from the viewing audience.
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Okay now, look carefully at the data and using the information in the following diagram,
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work with your fellow students to answer the questions as read aloud by Rich Silcox.
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As the distance increased from 50 meters, what happened to the mean time?
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Use the formula, percent of experimental error, equals calculated value minus the
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accepted value, divided by the accepted value, times 100, to calculate the percentage of
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error at 50 meters and 300 meters.
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Why do you think they are different?
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The speed of sound is directly proportional to air temperature.
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Is the speed of sound faster in the summer or winter?
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Why?
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All right, we're back, and with me are Rich Silcox and Dennis Huff to answer your questions.
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But let's start things off by asking Dennis, what is it, Dennis, that you actually do there
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at NASA Glenn?
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I'd be glad to answer that.
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Hello, my name is Dennis Huff, I'm the chief of the acoustics branch at NASA's Glenn Research
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Center that's located in Cleveland, Ohio.
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Our contribution to quieting the skies looks at ways to making the engines quieter.
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Our goal is to develop engine noise reduction technology without compromising the engine
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performance or the aircraft's safety.
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Some members of our team develop mathematical models to be able to predict the sound from
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the engine, while others test different parts of the engine inside wind tunnels and anechoic
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chambers.
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Our best noise reduction concepts will eventually be tested on engines to make sure we can really
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make the airplanes quieter.
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You've got a lot of good stuff going there that I could ask a lot of questions about,
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and I just might do that, Dennis, but I've got some e-mail questions that have come in
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for both you guys.
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So let me start with an e-mail question.
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The first question is, does the shape of a plane affect the sound?
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And this is from Jonathan in Virginia Beach.
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Yeah, Shelley, the shape of the airplane does change the sound dramatically.
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For instance, when the airplane is coming in for a landing or taking off, the flaps
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in the landing gear are deployed.
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In that case, the flow is very dirty and it makes a lot more noise than when those components
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are stowed away.
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Yes, and in fact, it's interesting on the engine itself.
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You'll notice that some of the older aircraft have smaller diameter engines, and the smaller
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diameter actually passes a lot more flow at a higher velocity, and this causes the jet
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noise to be very loud.
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We have a general rule of thumb that we say that the velocity of the exit of the velocity
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raised to the eighth power is proportional to the jet noise.
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So the newer aircraft that have larger diameter engines actually end up being quieter.
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All right.
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Let's go back.
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You've probably kind of answered this already, but I'm thinking about me who flies an awful
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lot on these small little, they call them puddle jumpers, or commuter planes compared
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to your bigger 757s.
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How is there a difference on those size of engines and the noise that they are generating?
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Sure.
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Those engines are some of the newer engines.
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We call those higher bypass ratio engines, and so you've got a lot of flow going through
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that.
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It's a lot of thrust in that engine, but it's going at a lower velocity, so it's a much
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quieter engine than the older ones.
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Oh, okay.
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In a lot of cases, the propeller airplanes are quieter, too.
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They're quieter than the large jets are.
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All right.
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I've got a question.
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You keep talking about research to reduce noise around communities.
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What is the community that you all are referring to here?
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Well, generally we're talking about that area around the airport that's affected by the
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operations of the airplanes taking off and landing.
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Once the airplane climbs to altitude and is at cruise altitude, maybe at 35,000 feet,
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you don't really hear it much anymore.
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Okay.
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All right.
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Good.
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Well, I've got someone telling me we've got a caller out there, so let's go ahead and
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take that caller.
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Caller, could I have your first name, please, and your question?
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My name is Timothy, and my question is, how fast is the sound of sound travels through
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water?
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Oh, okay.
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The sound traveling through water.
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And is there a difference between the speed that sound travels in air and water?
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Yes.
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The speed travels through water much more quickly than it does in air.
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I can't recall the exact number.
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I think it's three or four times faster in water than it is in air.
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Okay.
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All right.
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So we know that it is going to travel faster through water than in air.
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Good question there, Timothy.
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I'm going to take a final question I have here by email very quickly.
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Well, no, final advice.
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What advice would you, Dennis, give to viewers about thinking about careers?
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I'd be glad to answer that.
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My father gave me the advice to keep your options open.
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You can get into a lot of different activities and make sure you involve yourself in extracurricular
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activities, but also stay with your math and science and your English.
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All the different courses are very important.
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All right.
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There, you've heard it from us.
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And I see we're quickly running out of time.
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Thank you, Dennis and Rich.
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And now, students from Jonas Clark Middle School in Lexington, Massachusetts, share
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some technology notes that are sure to sharpen your investigation on sound following this
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program.
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One part of the website is called the NASA Sound Machine.
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With it, you'll learn about the shapes and characteristics of sand waves, how an
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airplane produces different kinds of noise, and what certain words would sound like if
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you had severe or partial hearing loss.
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Another part of the NASA Connect website features NASA researchers talking about their jobs.
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It's called Career Corner.
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There's also a fun quiz that will test your knowledge of sound and hearing.
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- Idioma/s:
- Materias:
- Matemáticas
- Niveles educativos:
- ▼ Mostrar / ocultar niveles
- Nivel Intermedio
- Autor/es:
- NASA LaRC Office of Education
- Subido por:
- EducaMadrid
- Licencia:
- Reconocimiento - No comercial - Sin obra derivada
- Visualizaciones:
- 448
- Fecha:
- 28 de mayo de 2007 - 16:53
- Visibilidad:
- Público
- Enlace Relacionado:
- NASAs center for distance learning
- Duración:
- 07′ 29″
- Relación de aspecto:
- 4:3 Hasta 2009 fue el estándar utilizado en la televisión PAL; muchas pantallas de ordenador y televisores usan este estándar, erróneamente llamado cuadrado, cuando en la realidad es rectangular o wide.
- Resolución:
- 480x360 píxeles
- Tamaño:
- 44.96 MBytes
