Reading assignment: 17.3,17.4
If the "sound level" of a noise changes by 20 dB, by how much did the
20 dB = a factor of 100 change in the intensity. I = 10^(dB/10)
Section 17.4 discusses both the Doppler effect and shock waves. How/why are they
related? Hint: compare Fig. 17.10 to Fig. 17.11
Figs 17.10 and 17.11 both involve sound waves being emitted from a changing location. The Doppler effect happens when the source is moving slower than the sound wave; the change in origin for the new waves causes the wave crests to be closer together (higher in pitch) for Observer A. A shock wave (sonic boom) happens when the source is moving faster than the sound wave; the change in location of the new waves causes a whole set of wave crests to reach the observer at the same time.
Return to Course Page