Submarines and anti-sub destroyers aren't using their sonar to listen for the sound of the motor. They're listening for cavitation from the screws. Motors are already silent-enough. The problem for stealth is how to make a silent mechanism for moving water.
Submarines and anti-sub destroyers aren't using their sonar to listen for the sound of the motor. They're listening for cavitation from the screws. Motors are already silent-enough. The problem for stealth is how to make a silent mechanism for moving water.