How does the Doppler effect change wave speed?

It doesn't change wave speed at all.
It only changes the wavelength perceived by the observer if he is moving toward or away from the source.
Notice that if one observer is moving toward a source, and another one is moving away from the same source, then one observer would see an abnormally long wavelength, and the other one would see an abnormally short wavelength, both from the same source.
The Doppler Effect ... like beauty ... is in the eye of the observer.

Answered by AL2006 | 2024-06-10

The Doppler Effect changes the perceived frequency and wavelength of waves based on the relative motion between the source and observer, but does not alter the actual speed of the wave in a given medium. For example, an observer moving toward a sound source will hear a higher frequency, while moving away will result in a lower frequency. The speed of the wave remains constant regardless of these changes.
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Answered by AL2006 | 2024-12-17