1. Exploring Pitch.
You hear a loud noise. Which wave property (frequency, wavelength, wave speed, amplitude, wave number, phase, etc.) do you think is related to the pitch?
Section 7.11 The Doppler Effect
Exercises Warm-up Activity
The frequency of a sound wave changes if there is relative motion between the emitter and the listener.
Definition 7.11.1. The Doppler Effect.
The frequency of a sound wave heard by a listener is not always the same as the frequency created by the emitter:
\begin{equation*}
f_{\text{listener}} = f_{\text{emitter}}\frac{\nu_{\text{sound}} + v_{\text{listener}}}{\nu_{\text{sound}} - v_{\text{emitter}}}
\end{equation*}
Each velocity (of the source or the listener) is positive if it is moving in the direction of the other but negative if it is moving opposite the direction of the other, relative to the medium through which the wave is moving. As you saw previously, the speed of sound in air is about 343 m/s.
Exercises Activities
1. Explore Doppler Shifts.
How does the detected frequency change if the listener is moving away from a stationary emitter? How does the detected frequency change if the emitter is moving away from a stationary listener?
References References
[1]
Fire Engine Siren Demonstrates The Doppler Effect by davidrobert2007.
