A Fourier Into the World of Sound

MEBBEM feat. KohlKohl CoffeyBrandon Kearns

Michaela HowardEmma Zelus

Experiment Basics

Description: Using two configurations of speakers and recorders, we will verify the Doppler Effect and analyze air density, sound intensity, and frequency data in order to find a relationship among altitude, air density, and sound waves.

HypothesisDoppler Effect - If a source emits a constant frequency, and the receiver moves away from the source at a sufficient velocity, the received frequency will be smaller than the emitted frequency.

Air Density and Sound - With increasing altitude, the density of air decreases. With lower air density, the speed of sound increases along with the frequency of sound.

Experiment Method: Doppler Effect

• On the ground, there was a frequency generator and a large speaker. The speaker emitted a constant frequency.

• On our balloon, we had a Dan Gibson parabolic dish with a microphone positioned at the focal point of the dish. Connected to the microphone was a recorder that will record the received sound for later analysis.

• We unravelled the rope attached to the weather balloon so as to achieve the maximum possible constant upwards velocity during our data collection period.

Experiment Method: Air Density and Sound

• The speaker emitted sound at constant frequency and intensity, whilst the recorder merely recorded the sound. When we were ready to commence the launch, we will play the emitted sound and begin recording.

• The S4 Instrument Kit continuously collected data for pressure, temperature, and position over time.

• We halted the progress of the balloon at 50, 150, 500, and 1000 feet for 5-10 minutes each in order to allow the S4 Instrument Kit to acclimate and collect consistent data for a considerable time period.

Experiment Analysis: Doppler Effect

• Measured emitted frequency

• Measured received frequencyo FFT Software

• Measured velocity of receiver

• Verified, with the measured received frequency data, that the frequency did decrease as the balloon moved farther away

• Compared the calculated doppler effect (Doppler Equation) with the measured doppler efffect

Experiment Analysis: Air Density and Sound

• Collected data for altitude, y position over time, temperature, and air density using S4 Data.

• Used FFT Software to analyze change in frequency over time -> compare with altitude

• Used Sound Analysis Software to analyze change in sound intensity with altitude

• Analyzed the relationships between altitude, temperature, air density, sound intensity, and sound frequency

Data Collection

Doppler EffectWe gathered data for the frequency with respect to time as the balloon traveled upward

We experienced issues with collecting sound data due to malfunctions with cables

Air Density and Sound

We gathered data for the change in air pressure with respect to altitude

We gathered data for the change in frequency with respect to time

Analysis and Conclusion

Analysis and Conclusion (cont’d)

Frequency: constantAt 2002 Hz

No change in Frequency withrespect to airpressure