When standing on deck while underway, you can definitely hear the sonar ping. It doesn't sound like the ping in the movies. It actually sounds like a bird chirp, maybe a parakeet, though you can't really localize the sound source, since it comes from a distributed source, that is, the surface of the water surrounding the ship. read more
In active SONARS, sound is emitted either omnidirectionally, or along a particular bearing (there are active beamformers as well as passive ones) and when the soundwave strikes an object, a portion of the sound is reflected back to the SONAR array which can show the range and bearing of the object reflecting the sound. read more
Active sonar is also used to measure distance through water between two sonar transducers or a combination of a hydrophone (underwater acoustic microphone) and projector (underwater acoutic speaker). A transducer is a device that can transmit and receive acoustic signals ("pings"). read more