Question

Three sources of sound are distributed along a line, as shown in the figure. v is the speed of sound. Source A is at rest, and it emits sound waves with a frequency of 480 Hz. Source B is traveling at v/5 to the right, and it emits sound waves with a frequency of 960 Hz. Source C is traveling at a speed of v/3 to the left, and it emits sound waves with a frequency of 1550 Hz. A, B, and C also detect the sound waves emitted by the other sources. All the questions below pertain to when the three sources of sound are at the locations shown in the figure below.



a)What frequency does A observe for the waves emitted by B? (A = observer; B = source)

b) What frequency does C observe for the waves emitted by A? (C = observer; A = source)

c)What frequency does B observe for the waves emitted by C? (B = observer; C = source)

Answer 1

a. Fa = ((V-Va)/(V+Vb))*Fb
Fa = ((343-0)/(343+68.6))*960 = 800 Hz

b. Fc=((343+114.33)/(343-0))*480=640 Hz.

c. Fb = ((343+68.6)/(343-114.33))*1550
Fb = 2790 Hz.