[svandamme]

it's not the boom that is tell tale
it's the lack of sound coming from the plane as it approaches...

if it's sub sonic, you'de hear something
if it's supersonic, you would not

there is sound allright, but that's carrier deck operations , not the sound of the jet that is inbound...that would be a lot louder , would be closer to the sound as it is moving away from the camera...just a tad less