If you are in a submarine, and if there is a vessel or craft using active sonar, you will hear it, pretty much guaranteed; if you are hearing active sonar while you are in a submarine, chances are that you are the reason that the water in your vicinity is being ensonified. read more
Active sonar systems do use frequencies that are within our ability to hear them so it could be possible to hear an active sonar ping if your ears were in the water. Depending on how close you were to the source, the experience could be very unpleasant. read more
I was a Sonar Operator/Supervisor on two attack submarines, USS Baton Rouge and USS San Francisco and it's exceedingly easy to hear the use of active sonar. It's also possible to hear ultrasonic transmissions through the use of band-shifting instruments such as the old RYCOM. read more
If you are in a sub and you hear another's active sonar, you are in trouble. Of course hunting subs rarely use active sonar, it can be tracked back to the source. read more