Overcoming naïve mental models in explaining the Doppler shift: An illusion creates confusion

A perceptual auditory illusion is described that may contribute to students' misunderstanding of the physical principles of the Doppler shift. The illusion advances the formation of naïve mental models about the change in observed frequency that occurs as a sound source passes a stationary observer. Factors that may cause misunderstanding are addressed including the following: (i) the semantic distinctions between physical "frequency" and perceptual "pitch," (ii) the influence of dynamic loudness on pitch, and (iii) the ambiguity of the word "rise" in describing the wave mechanics of the Doppler shift. Implications for teaching the principles of the Doppler shift include addressing the origin of naïve beliefs and using the illusion as a salient and conspicuous example of a breakdown of the correspondence between physics and perception.