Which of the following is most likely to happen when a sound wave reflects
off a hard surface? (Assume that neither the source of the sound nor the hard
surface is moving.)
A. A change in speed
B. An echo
C. A change in pitch
D. A beat frequency
an echo is caused by the fact that waves can be reflected by solid surfaces, this is due to the dynamic pattern of rarefactions and air seals near the reflecting surface
