Check all that are true about the Doppler Effect. please alert your teacher that this picture is missing Group of answer choices A sound wave moving away from you has a lower pitch and frequency. As a wave comes towards you, it has a lower frequency because the waves spread out. The Doppler Effect is the change in loudness of a sound wave when the source is moving. The Doppler Effect is the apparent change in frequency of a wave when the source and observer are moving with respect to each other. All waves can be Doppler Shifted.