# Homework Help: Need help with physics experiment (Speed of sound)

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1. Sep 4, 2015

### yulija

< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown >

Last week we had to conduct an experiment with the aim of determining the speed of sound. I decided to play with doppler effect.
I was more or less sure what I had to do but then the teacher came and changed a whole set up.
The outcome: I am currently very confused because I have to write a report on this experiment.

Anyway, what I did was observing doppler effect in circular motion (with stationary source and moving observer). Basically speaking, I was swinging a microphone in a circle next to the sound emitting source that collected data into my computer. I also tried two different frequencies - 1000 and 4000Hz.

So now I have four graphs of sound pressure against time: two of them show data when everything was stationary. And other two show the data with doppler effect.

I can also convert them into amplitude versus frequency graphs.

So.. what do I do next?? Is there a way of determining speed of sound out of that?

Last edited by a moderator: Sep 4, 2015
2. Sep 4, 2015

### DEvens

Welcome to the forum.

Can you determine from your graphs how fast the microphone was moving? Did you, for example, measure the radius of the path the microphone moved through? If you did not then probably you will not be able to complete this. You will probably be able only to determine the speed of sound in multiples of the unmeasured speed of motion of the microphone.

Have you got a formula for the Doppler effect as a function of speed of motion of the microphone, speed of sound, and frequency? If you don't, can you derive it? Or Google it.