Question

In the 1986 film Top Gun. The aircraft used in the film were given a fictional name, but the jet used in filming was the Northrop F-5E Tiger. In this scene, the director wanted a supersonic flyby, but the stunt pilot kept the speed at 300 knots (154 ?⁄?) for safety reasons.

1. At this speed, the F-5E’s engine produces a sound with a frequency of 560 ??. What frequency would someone in the tower hear during this flyby?

2. At a distance of 30 ? from the jet, you would hear a 140 ?? sound level. What would the maximum sound level be (in ??) at the tower during the flyby, assuming the jet gets as close as 50 ? to the tower?

Answer 1

The speed of the plane (source) Vs = 154 m/s

The speed of sound is V = 343 m/s

The source frequency is fs = 560 Hz

usign doppler effect , the frequency that the ground obeserver will hear when the plane is approaching is  is w

putting the value we get f = 811.4 Hz

The sound pressure level is P1 = 140dB at r1 = 30 m

the sound pressure level at r2 = 50m be P2

the sound pressure level is connected wit the distance with the relation by

putting the values in the equation we get

P2 = 84 dB

so the pressure level is 84 dB