Question

A siren emits a sound at 1700 Hz. Assume a speed of sound of 332 m/s. What frequency would a stationary observer hear if the car with the siren is travelling at:A. 25 m/s towards the observerB. 25 m/s away from the observerC. 140 km/h towards the observer

Answer 1

F source = 1700 HZ

v= source

S sound =332 m/s

Doppler equation:

F listener = F source ( speed of sound / speed of sound - v source)

A) v source 25 m/s

F = 1700 hz ( 332 m/s / 332m/s - 25m/s) = 1,838 HZ

B) v = - 25 m/s

F = 1700 hz ( 332 m/s / 332m/s + 25m/s) = 1581 HZ

C) 140 km/h = 39 m/s

F = 1700 hz ( 332 m/s / 332m/s - 39m/s) = 1,926 HZ