Header Bar Graphic
Shuttle Image and IconAerospace HeaderBoy Image
Spacer TabHomepage ButtonWhat is NASA Quest ButtonSpacerCalendar of Events ButtonWhat is an Event ButtonHow do I Participate ButtonSpacerBios and Journals ButtonSpacerPics, Flicks and Facts ButtonArchived Events ButtonQ and A ButtonNews ButtonSpacerEducators and Parents ButtonSpacer
Highlight Graphic
Sitemap ButtonSearch ButtonContact Button

UPDATE #36 - October 9, 1998

PART 1: NASA K-12 Online Aeronautics project
PART 2: Upcoming Chats
PART 3: Project News
PART 4: Six Decibels per Doubling
PART 5: Subscribing & Unsubscribing: How to do it


   Wednesday, October 14, 1998
       1:00 pm - 2:30 pm Pacific (4:00 pm - 5:30 pm Eastern)
       During this event we will introduce you to four exciting online
        projects. If you are unable to join us for the
        entire event we have provided approximate times that will allow
	you to attend the portion of the program that
        is the most relevant to you:
              1:00 pm - 1:05 pm Pacific (4:00 pm - 4:05 pm Eastern)

              1:05 pm - 1:25 pm Pacific (4:05 pm - 4:25 pm Eastern)
              Grades K-2
              Off to a Flying Start

              1:25 pm - 1:45 pm Pacific (4:25 pm - 4:45 pm Eastern)
              Grades 5-8
              Aerospace Team Online

              1:45 pm - 2:05 pm Pacific (4:45 pm - 5:05 pm Eastern)
              Grades 9 - 12
              FoilSim: Basic Aerodynamics Software

              2:05 pm - 2:25 pm Pacific (5:05 pm - 5:25 pm Eastern)
              Grades K-14
              Cooperative Agreement Aeronautics Projects

              2:25 pm - 2:30 pm Pacific (5:25 pm - 5:30 pm Eastern)
              Wrap-up and web chat

       Technologies Available During the Live Events:
       (Caution: These links may not be active until the time of the
              For more information go to


Wednesday, October 14, 1998, 1:00 p.m. Pacific Time: Fanny Zuniga,
aerospace engineer

Fanny spends most of her time conducting experiments and studying data to
help build better airplanes and space vehicles. She is currently working
with a group on the High-Speed Research project. Their goal is to build a
new airplane capable of carrying up to 300 passengers and flying at about
twice the speed of today's commercial transports. Fanny will answer
questions in english and spanish.
Read Fanny's autobiography at
Register for this chat at http://quest.arc.nasa.gov/aero/chats/#chatting

Friday, October 16, 1998, 10 AM Pacific Time: Stephen Jaeger,
aeroacoustics engineer

Aeroacoustics is the study of aircraft noise. Stephen's responsibilities
in this area include developing tools for measuring aircraft noise, and
conducting acoustics research on wind tunnel models of supersonic jets,
airliners and aircraft engines.
Read Stephen's autobiography at
Register for this chat at http://quest.arc.nasa.gov/aero/chats/#chatting


Collaborative Events To Begin!

Several new aeronautics projects will have students working
collaboratively online. One activity is targeted for elementary and middle
school classes. Two others will be for high school or junior high school
kids. These higher end activities might not be done as an entire class;
other users may include science clubs, GATE kids or science fair folk.

The ELEMENTARY / MIDDLE SCHOOL - Right Flying on-line collaborative
activity is now online.

The HIGH SCHOOL / JUNIOR HIGH SCHOOL - Free Flight Analysis: an
"in-flight" movie"
and HIGH SCHOOL / JUNIOR HIGH SCHOOL - Wind tunnel building activities
will be online next week. For more information go to

All of us at Quest hope you will consider joining us for this online
festival of learning.

Wright Flyer Coloring Contest

Which category will you choose for your entry "Most Realistic" or "Most
Patriotic"? Check out all the categories and join the fun.

Hey those of you who are good a graphics programs, let's see what you come
up with!!

To find the details go to

[Editor's Note: Stephen Jaeger is an aeroacoustic engineer. He's the guy who's helping engineers design quiet airplanes. Read his bio at: http://quest.arc.nasa.gov/aero/team/jaeger.html This journal with pictures can be found at http://quest.arc.nasa.gov/aero/team/fjournals/jaeger/6db.html


by Stephen Jaeger

September 10, 1998

It was a crazy summer. I was very busy at work, I took a class at Stanford
and I got married...all in one summer!

Two months ago we finished up our wind-off calibration of the new 40- by
80-Foot Wind Tunnel test section. (Wind-off means we didn't turn the wind
tunnel on. We will do the wind-on calibration later this month.) For the
wind-off calibration, we were interested in how much of an echo we were
going to get from the walls of the wind tunnel.

During the first month we fired off pistols and cannons and other noise
sources to measure the reflections as I discussed before. The remaining
part of the test was an assessment of the decay properties of the test

Imagine you are out in the middle of a field somewhere. In front of you is
a loudspeaker with your favorite music playing. As you move away from the
speaker the music will get quieter and quieter until you can't hear it at
all. In fact, you may notice that the loudness of the music will decay
rapidly as you first start to move away. However, when you
are further away, you will have to walk a much greater distance to notice
anymore change. Try it sometime.

This phenomenon is well known in science and applies to other "point
sources" such as light and radio waves. Sometimes acousticians call it the
"6 dB per doubling law." It says that the sound pressure will decrease by
6 decibels each time you double your distance from the speaker. So if the
speaker is screaming at 100 dB at 10 feet away, it will still be at 94
decibels from 20 feet away. (A decibel (dB) is a measure of sound
pressure. A whisper is about 50 dB, someone talking is about 70 dB, a jet
plane might be 100 dB, and a rock band might get to 120 dB near the

The above is not true in a room, however. Because of all the reflections
from the walls the noise can still be loud even from far away. This is why
a basketball game is so much louder inside an auditorium than it is on an
outside court. For our wind tunnel, we want the noise environment to be
the way it would on the outside. One way to test this is to
place a noise source at one end of the tunnel and position a microphone at
different distances from the source and determine if the sound does indeed
follow the "6 dB per doubling law." Of course it won't because we're in a
big room, but we can get close to it if we designed the room correctly.

We used three noise sources to test the decay:

 1) An 18-inch woofer in a speaker cabinet. The woofer provides low
frequency noise.

 2) The dodecahedron. The dodecahedron is a 12-sided ball
 with twelve 8-inch speakers mounted in each face. The
 dodecahedron is supposed to radiate mid-range frequency
 sound evenly in all directions.

 3) The "Screaming Ted." The Screaming Ted Nugent, or Screaming Ted
(named after a loud heavy metal guitarist from another era), produces
 ultrasonic white noise. It sounds like a high pitched hiss. Most of the
sound generated by the Screaming Ted can't even be heard by humans, but
 dogs can probably hear most of it!

With each of these noise sources we measured the decay of the noise with
distance at different frequencies. We are still analyzing the data but it
seems that we have a pretty good anechoic wind tunnel. This is a good
thing because it cost you $25 million.


If this is your first message from the updates-aero list, welcome!

To catch up on back issues, please visit the following Internet URL:

To subscribe to the updates-aero mailing list (where this message
came from), send a message to:
In the message body, write only these words:
   subscribe updates-aero


To remove your name from the updates-aero mailing list, send a
message to:
In the message body, write only these words:
   unsubscribe updates-aero

Footer Bar Graphic
SpacerSpace IconAerospace IconAstrobiology IconWomen of NASA IconSpacer
Footer Info