McNeese LAACES Group Sound Experiment

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McNeese LA-ACES Group Sound Experiment

• Columbia Scientific Balloon Facility
• Palestine,Tx May 2007

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Team Members

• Tate Townsend- Team leader and mechanical design
• Travis King- Software and Data analysis
• Ajeeta Katiwata-Science
• Satish Shreta-Science
• Katie Graves- Materials Aqcuistion

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Scientific Goal

• Record environmental noise as it correlates to
  different flights events as the transition to
  different layers of the atmosphere and dynamical
  events as the release of the payload from the
  balloon, the bursting of the balloon, landing,
  etc.
• Measure the changes in the velocity of sound as a
  function of altitude and compare those changes
  with theory based on standard atmosphere model
  and ideal gas relationship between velocity and
  temperature.

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The Sound of Titan inspiration for MLAGSE

• The Huygens probe piggy-backed on Cassini, a
  spacecraft exploring the Saturns system.
  Eventually, Huygens descended through the thick
  atmosphere of Titan, Saturns largest moon.
• Audio data was collected by the Huygens
  Atmospheric Structure Instrument (HASI), which
  includes an acoustic sensor, during Huygens'
  descent, 14 January 2005.
• http//www.esa.int/SPECIALS/CassiniHuygens/SEM8
  5Q71Y3E_0.html

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Alien Sounds

• This is the first sound recorded on another world
  (as far as we know).
• Titan atmosphere is very thick (thicker than on
  Earth at the sea level).
• Can you hear sound on Mars (or Earths
  stratosphere?) We are going to find out.

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Velocity of Sound in the Atmosphere

• The velocity of sound is a term used to
  describe the velocity of sound waves passing
  through an elastic medium. The speed varies with
  the medium employed (for example, sound waves
  move faster through water than through air), as
  well as with the properties of the medium,
  especially temperature. The term is commonly used
  to refer specifically to the velocity of sound in
  air. At sea level, at a temperature of 21 C
  (70 F) and under normal atmospheric conditions,
  the speed of sound is 344 m/s

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Velocity of Sound in the Atmosphere

• The velocity of sound varies depending on
  atmospheric conditions the most important factor
  is the temperature Air pressure has almost no
  effect on sound speed. Air pressure has no effect
  at all in an ideal gas approximation, because
  pressure and density both contribute to sound
  velocity equally, and in an ideal gas the two
  effects cancel out, leaving only the effect of
  temperature. Sound usually travels more slowly
  with greater altitude, due to reduced temperature
  (but speeds up in the stratosphere due to heating
  within the ozone layer). Humidity has a small,
  but measurable effect on sound speed. Sound
  travels slightly (0.1-0.6) faster in humid air.
  The approximate speed of sound in 0 humidity
  (dry) air, in meters per second, at temperatures
  near 0 C, can be calculated from

Where T is the temperature in degrees Celsius.
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Velocity of Sound in the Atmosphere
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Velocity of Sound in the Atmosphere Velocity and
Temperature vs Altitude
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Velocity of Sound in the AtmosphereVelocity and
Percentage Diff (with respect to the ground) vs
Altitude
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MLAGSE experiment to measure sounds velocity

• According to the standard wave relationship
  between velocity, wavelength and frequency

if we produce a wave with fixed frequency a
change in velocity will result in a change in
wavelength. Measuring the wavelength will allow
us to calculate the change in the velocity of
sound. We can measure the wavelength of the wave
with a simple experimental setup.
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There is an arrival time LAG between the two
microphone, that we can use to measure the
wavelength of the sound wave.
Sound with a simple sinusoidal signal With a
fixed frequency of 500 Hz
Microphone 1 Left channel
Microphone 2 Right channel
9 cm
Speaker
MP3 Digital Recorder Stereo HQ (44100 Hz
Sampling Frequency)
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Mathematical model of the sound amplitude
recorded by the microphones.
If we set the origin at the first microphone the
sound wave amplitude can be described as
Frequency of the speakers sound wave
where
At the same instant of time the amplitude at the
second microphone will be
Where
Distance between the microphones
wave number
With some simple math tricks we can extract the
value k from the data (and therefore measure the
wavelength).
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Math used to extract the velocity from our
data(if you are interested)
Start with adding the two signals and using the
trig identity
Constant
We obtain
So the sum of the two signals is a simple sine
function with frequency f. For any given sine
function
It is well know that
Then in our case we have that
then
and
and finally
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Results from our experiment (room temperature, 21
Celsius, sea level)
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500 Hz
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Mission Operations

• The recorder and the MP3 player will be started
  and data will begin to recorded.
• All components will be placed properly inside the
  box and sealed.
• The DVR will actually begin collecting data about
  15 minutes before the launch. We will use stop
  watches to record the correct launch time to
  synchronize our data with the altitude
  information.

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Payload Design

• The main part of the payload is the two Digital
  Voice Recorders.
• MP3 player produces our control sound wave, a
  sine wave.
• Two microphones will record sound.
• A speaker will emit the sine wave.
• Two 5 watt resistive heating elements.

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System Design

• A DVR will be connected in stereo to two separate
  microphones. A MP3 player will produce the sine
  wave through a speaker mounted on the side of the
  box.

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Thermal Design

• Two 5 watt resistive heating elements will
  attempt to keep the inner structure warm.
• Also, tests performed on the box found that it is
  quite resistive to temperature change when
  covered in aluminum foil and a reflective tape.
• Some worry about ability of heating elements to
  keep box warm for long periods
• of time (we did some but not throughout
  testing).

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Data Acquisition and Analysis

• Data will be recorded to the Digital Voice
  Recorder.
• Sampling Frequency will be 42,100 Hz.
• The DVR will be able to record over 35 hours of
  high quality sound (42 khz).
• The data is easily extracted via USB onto our
  computers.
• Data will be analyzed using MatLab.

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Budget

• Expense Budget
• Recoder 111
• MP3 Free
• Microphones 30
• Foam Board and
• other materials for box 20
• Speaker 20
• Chance to work together
• And learn teamwork Priceless
• ________________________________
• Total 181

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Budget Cont.

• Weight Budget
• Box and inner structures 220g
• DVR 60g
• MP3 35g
• Speaker 100g
• Microphones 5g
• AAA Battery 30g
• Heating Element 20g
• Wires 10g
• TOTAL 480g

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Special Thanks . . .

• Dr. Santostasi
• Mr. Archer
• LA-ACES Organizers
• NASA Employees