Year 11 Physics - App of 'Beats': Aircraft Engine shutdown

'Beats': When 2 sound waves of slightly different frequencies interfere. When these waves overlap, they create a new wave pattern via alternating constructive and destructive interference creating an alternating sound between 'soft' and 'loud' (called 'beats').
In the case of this Airbus A330, it has 2 engines and when the Captain turns off the engines one at a time, each engine shutdown produces sound waves at slightly different frequencies.
Take 'Engine 1' producing a sound at f = 500 Hz and 'Engine 2' at 495 Hz.
​When these two engines are running and their sounds combine, the interference pattern they create will produce beats.
Then the beat frequency = | 500 Hz - 495 Hz | = 5 Hz.
This means that the combined sound will have a fluctuation in volume (a beat) 5 times per second.
As someone in or near the aircraft, you'd hear a sound that seems to get louder and then softer 5 times every second. This is because the two engines are slightly out of sync, causing their sound waves to alternately amplify and cancel each other out.