Experimental Determination of the Sound Speed by the Doppler Effect of a Rotating Sound Source

In this work, we propose an experimental method to measure the speed of sound through the Doppler effect generated by a rotating sound source. The method is compared with the conventional resonant tube method, based on the measurement of acoustic resonance frequencies in a tube with one end closed. Although the didactic use of a rotating sound source to demonstrate the Doppler effect is not new, we did not find in the literature a detailed procedure for data acquisition and quantitative treatment using the full description of the time varying frequency in the laboratory reference frame. This experimental procedure was formulated by students and professors from the Aeronautics Institute of Technology and applied in the physics laboratory of the FIS-26 (Mechanics II) course. We consider that the experimental procedure presented here in detail could be useful for a wider audience working with physics teaching at university and secondary level.

Keywords:
Mechanical waves; Doppler effect; waves; speed of sound