The rise in pitch of an approaching siren is an apparent increase in its:
A)speed
B)amplitude
C)frequency
D)wavelength
E)number of overtones

Question

Quizplus · Accepted Answer

The rise in pitch of an approaching siren is due to the increase in frequency of the sound waves it produces. As the source approaches, the sound waves are compressed, increasing the number of waves that pass by per unit of time (i.e. increasing the frequency). This translates into a higher pitch that is heard.

The Rise in Pitch of an Approaching Siren Is an Apparent