But in these cases the term 'voice' is inappropriate; the more
correct expression would be 'sound'. For the scallop, when it goes
along supporting itself on the water, which is technically called
'flying', makes a whizzing sound; and so does the sea-swallow or
flying-fish: for this fish flies in the air, clean out of the water,
being furnished with fins broad and long. Just then as in the flight
of birds the sound made by their wings is obviously not voice, so is
it in the case of all these other creatures.