The answer to this question is C. Â The reason why this is an incorrect statement is that the Doppler effect takes into account two moving objects. Â In this scenario, both the source and the listener are stationary to the frequency of the sound waves will not change due to the Doppler effect. Â For the other answers, the frequency of sound waves is not affected by nature of the medium. Â The distance between a sound source and listener does not alter the frequency of the sound wave. Â The frequency of the sounds waves remains the same to the listener.