OVERCOMING NAIVE MENTAL MODELS IN EXPLAINING THE DOPPLER-SHIFT - AN ILLUSION CREATES CONFUSION

A perceptual auditory illusion is described that may contribute to stu dents' misunderstanding of the physical principles of the Doppler shif t. The illusion advances the formation of naive mental models about th e change in observed frequency that occurs as a sound source passes a stationary observer. Factors that may cause misunderstanding are addre ssed including the following: (i) the semantic distinctions between ph ysical ''frequency'' and perceptual ''pitch,'' (ii) the influence of d ynamic loudness on pitch, and (iii) the ambiguity of the word ''rise'' in describing the wave mechanics of the Doppler shift. Implications f or teaching the principles of the Doppler shift include addressing the origin of naive beliefs and using the illusion as a salient and consp icuous example of a breakdown of the correspondence between physics an d perception. (C) 1997 American Association of Physics Teachers.