1. The problem statement, all variables and given/known data Hello, I did an experiment a couple of weeks ago to measure the doppler-effect. I have used a pendulum with a microphone attached to it. At one end i put a speaker wich produces a sound with f =440 hz. T of the pendulum = 1,86 s. Vmax = 1,69 m/s. But if i try to measure T in my diagram it doesnt come near the solution i get with the doppler-equations. I have done this in my diagram: 1800 - 1100 = 700 ms 7T = 700 ms => T = 100 ms = 0,1 s I get f ≈ 10 hz (see doppler-effect2) 2. Relevant equations I used fw=fb(1 + (vw/v)) and fw=fb(1-(vw/v)) and i got fw = 442 hz when the microphone is moving towards the speaker and fw = 437 hz when it moves away from it. 3. The attempt at a solution I have tried to change the time-axes with a other timescale. But i dont think that's the solution. I know v is not constant. I don't see a way to link my experiment with the theory. I hope someone can help me with this.