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Speed of Sound

Speed of Sound. Team BalloonWorks. Table of Contents. Mission Goal Science Objectives Technical Objectives Science Background Principles of Sound Propagation Earth’s Atmosphere Environmental Effects Applications Previous Experiments Expected Outcomes. Mission Goal.

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Speed of Sound

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  1. Speed of Sound Team BalloonWorks

  2. Table of Contents • Mission Goal • Science Objectives • Technical Objectives • Science Background • Principles of Sound Propagation • Earth’s Atmosphere • Environmental Effects • Applications • Previous Experiments • Expected Outcomes

  3. Mission Goal • Measure the speed of sound in Earth’s atmosphere in order to establish a relationship between speed of sound and altitude. • Consider the effects of temperature and humidity on the speed of sound up to an altitude of 100,000 feet.

  4. Science Objectives • Determine the general profile of temperature with altitude. • Determine the effects of humidity on the speed of sound. • Determine the relationship between temperature and speed of sound. • Measure the speed of sound with respect to altitude.

  5. Technical Objectives • Successfully reach an altitude of 100,000 feet • Obtain accurate and precise measurements for speed of sound • Measure temperature, pressure, and humidity • Withstand the atmospheric conditions such as low temperature and pressure • Withstand the impact upon landing

  6. Science Background

  7. Principles of Sound Propagation • Sound: Moving Pressure Wave in a Medium • Disturbance or vibration must be made • Mechanical pressure wave • Different wave transformations depending on the medium • Important Factors for Sound Waves in Gases • Temperature • Gas composition

  8. Earth’s Atmosphere • Troposphere • Surface to ≈ 20km • Temperature decreases • Stratosphere • ≈ 20to 50 km • Temperature increases • Mesosphere • Thermosphere • Exosphere

  9. Environmental Effects • Air is an Ideal Gas • ; γ= 1.4 • Temperature • ; R = 286 J/kgK

  10. Environmental Effects • Humidity will affect the composition of air • Larger RH will decrease ρand γ • A decrease in ρ will increase speed of sound • A decrease in γ will decrease speed of sound • Overall, an increase in RH causes a small increase in speed of sound

  11. Environmental Effects

  12. Applications • Sonic Detection and Ranging (SODAR) • Project Mogul • - Roswell UFO Incident

  13. Applications • Sound Navigation and Ranging (SONAR) • Active-Emits and receives pulses of sound • Passive- Only receives sound pulses from external sources • Ultrasound Doppler Vibrometer • Detects buried land mines • Huygens Probe • Measured speed of sound on Titan

  14. Previous Experiments • Data were used to graph the relation between microphone separation and time difference • Equation and time difference from software can be used to obtain speed of sound • Two microphones measure the time difference between sound waves

  15. Previous Experiments • Experiment by McNeese University • Design Apparatus • Measures the time difference between sound waves with two microphones Adjusted Data Points with Temperature

  16. Expected Outcomes • Decrease in speed of sound until the balloon reaches the stratosphere • Increase in speed of sound in the stratosphere • Humidity is expected to play a minor role in determining the speed of sound when compared to temperature changes

  17. Sources • Radford, Benjamin. "Does secret FBI file expose Roswell UFO? Likely not." . Discovery News and MSNBC, 13 Apr 2011. Web. 20 Nov 2011. <http://www.msnbc.msn.com/id/42575225/ns/technology_and_science-discovery_com/t/does-secret-fbi-file-expose-roswell-ufo-likely-not/>

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