Interactive LearningWare 16.2 provides some pertinent background for this problem. A convertible moves toward you and then passes you; all the while, its loudspeakers are producing a sound. The speed of the car is a constant 5.73 m/s, and the speed of sound is 343 m/s. What is the ratio of the frequency you hear while the car is approaching to the frequency you hear while the car is moving away?

The ratio of the frequency that is heard while the car is approaching [tex]f_{ap}[/tex] to the frequency that is heard while the car is moving away [tex]f_{ma}[/tex] can be calculated using the Doppler effect equation:

[tex] \frac{f_{ap}}{f_{ma}} = \frac {f_{0} \frac{v_{s} - v_{r}}{v_{s} - v_{e}}}{f_{0} \frac{v_{s} - v_{r}}{v_{s} + v_{e}}} [/tex]

where [tex]f_{o}[/tex]: is the emitted frequency, [tex]v_{s}[/tex]: is the speed of sound, [tex]v_{r}[/tex]: is the speed of the receptor and [tex]v_{c}[/tex]: is the emissor speed

[tex] \frac{f_{ap}}{f_{ma}} = \frac{v_{s} + v_{e}}{v_{s} - v_{e}} = \frac{343 + 5.73}{343 - 5.73} = 1.03 [/tex]

Therefore the ratio is 1.03.

I hope it helps you!