Examining Far and Near-Field Doppler Shifts

Overview

Objectives/Goals The objective of this project was to be able to determine how observed frequency shifts in a practical, classical Doppler effect setting at different distances between the emitter and moving observer (me, on my bicycle) and why. Methods/Materials I essentially attached my phone to the handlebars of my bicycle with the spectral analysis app opened, and rode my bike in a straight line in a parking lot. On that straight painted line I set up tape markers at different distances and later on I set up little clothes pin nubs on those markers to make a clicking sound as I rode over them. I set up my keyboard away from that line at different distances and would ride past as my father held a key on the board. I repeated multiple trials for different distances and saved the data on my phone before I transferred it to my computer. Results In the end, my results supported my hypothesis that larger, faster-appearing shifts would happen with the smaller observation distances and the opposite for the larger observation distances within each test distance. I had slightly off kilter results between some of the different test distances because of the fact that I'm a human and I was riding a bicycle, so I couldn't keep my speed exactly the same the entire time. I wrote a simple equation heavily based upon the classical Doppler Effect equation that I first used approximate the results from my individual runs. Once I saw that it worked accurately for these, I then used it to generalize what happens for different test differences and constant hypothetical speeds and it proved my hypothesis true. Conclusions/Discussion Today there are already tons of implementations of the Doppler Effect. Whether it's taking readings and measurements from blood, using redshift and blueshift to measure the spin of a galaxy, or navigation undersea, the Doppler Effect is extremely important. The experiment I have conducted this year demonstrates some of the basic principles of this phenomenon, and I discovered how sound frequency from our perspective shifts when you or the object making the sound is moving at different distances. This could be potentially important as I plan on using this new knowledge to find a way for police cars to track down illegal firework usage on July 4th.

Competition history

• CSEF 2016 Physics & Astronomy · Entry S1719

Resources

• CSEF project summary ↗

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