What is a sonar transducer?

Answer 1

A sonar transducer is the element in the sonar apparatus that turns the electrical signal into sound, which is mechanical energy, and then does the opposite for returning signals. A generator of some kind creates and amplifies the electrical signal, it is directed to the transducer, which then makes the conversion, and the pulse is sent out. The transducer then "listens" for returning energy, and converts anything that comes back into an electrical signal which is sent to the receiver. Sonar is (briefly) the use of sound (which is mechanical energy) to "look at stuff" in in water or other media. An electrical signal is generated by the equipment, and it is changed into mechanical energy by a special crystal in the same way a speaker changes electrical energy into sound we hear. The transducer is a piezoelectric crystal that works on the principle of the same name. Let's look at a transducer and see how it works, but first let's see what the underlying physics says about it. Piezoelectric crystals are crystals that change shape when we apply a voltage across the crystal. Depending on the placement of the leads that apply the voltage and the orientation of the crystal, it will expand or contract to a DC voltage. If we reverse the polarity of the applied voltage, the crystal will contract or expand (respectively) in just the opposite way. Applying an AC voltage causes the crystal to respond in that same way, and it will vibrate. These vibrations travel through the water or other media we are applying it to. The sonar transducer is a crystal mounted in a "holder" or some kind. It has electrical leads attached. The whole of this is "packaged" appropriately depending on whether it is going to be mounted on the hull of a vessel or held in the hand by an operator. A link is provided to a group of pictures of different types of transducers posted at Photobucket. Surf on over and have a look.