SONAR is the name applied to all underwater sound gear. Like radar, it is a coined name, taken from the words SOund Navigation And Ranging.

When a submarine submerges, radar becomes useless and no lookouts remain on deck. The periscope and the sonar gear are now the eyes and ears of the submarine. But in the vicinity of enemy ships, it may by dangerous to use the periscope very often. Then the submarine must depend chiefly on listening. The sonar operators become the main channel of information about the maneuvers of the enemy.

Ships make sounds

Any ship moving through the water makes a certain amount of sound. Most important to the sonar operator is the sound of enemy propellers as they churn through the water.

Illustration of propeller noise.
Next in importance to the sonar operator are the noises from various pieces of machinery within the ship. These sounds go through the hull and out into the water.   Illustration of machinery noise.
With the ship stopped dead in the water, propellers and machinery may both be silent. But even then some sound may come from the slapping of the waves against the ship's hull.   Illustration of propeller noise.
The purpose of sonar gear is to detect these various sounds

Sonar listening gear has 5 essential parts
1. Hydrophones. On a modern submarine there are three hydrophones: one topside and two just below the level of the keel.   Illustration of hydrophone locations.
2. Cables. A cable runs from each hydrophone through the submarine's hull.   Illustration of cable in sound head.
3. Receiver-Amplifiers. The other end of each cable is connected to a receiver-amplifier, which looks something like a radio.   Illustration of sonar amplifier.
4. Headphones. A pair of head phones can be plugged into the phone jack of each receiver-amplifier.   Illustration of headphones.
5. Training Mechanisms. Hand-operated and electrically controlled mechanisms turn the hydrophones in any desired direction.   Illustration of training mechanism.

The principles of sonar listening are simple
Illustration of ship sounds, hydrophone, cable, amplifier, training gear and headphones.  The sounds made by a ship are picked up when the hydrophone is trained in the ship's direction and are changed into electric currents which pass through a cable to the amplifier where they are strengthened so that the sounds can be hear in the headphones.

There are two main types

Sonic gear picks up sound you could hear with your own ears if you stuck your head out into the water.

The Hydrophone in sonic gear resembles a long bar and is mounted topside, either port or starboard, forward of the conning tower.   Photo of JP hydrophone.
The Amplifier at the other end of the connecting cable from the hydrophone is located in the forward torpedo room.   Photo of JP amplifier.
The Training Mechanism alongside the amplifier consists of a handwheel which turns the shaft on which the hydrophone is mounted. There is also a pointer and dial marked off in degrees.

JP is the Navy term for sonic listening gear. The J means that it can be used for listening only. The second letter P merely indicates the model.

  Photo of JP training mechanism.

of sonar listening gear

Supersonic gear picks up sounds too high for the human ear to hear and changes them into sounds which can be heard.


Drawing of WCA hydrophones.   The Two Hydrophones (Projectors) are mounted at the bottom of shafts, which extend through the hull under the forward torpedo room. Lowering these shafts puts the two projectors below the keel.
Photo of WCA amplifier.   The Receiver-Amplifiers, one for each projector, are located in the conning tower. They look alike and they both operate in the same way.
Photo of WCA remote control unit.   The Remote-Control Units, one for training each projector, are also in the conning tower, on top of the receiver-amplifiers. Actually the projector shafts are turned in the forward torpedo room, by training mechanisms run by electric motors.

JK/QC is the Navy term for one type of supersonic gear. The JK half of the combination projector is for listening only; the QC half can also be used for sending out sounds into the water.

QB designates the other type. As indicated by the letter Q, the QB projector can send as well as receive sounds.


Comparison of sonic and supersonic listening

Since enemy ships make sonic and supersonic sounds, both types of gear are necessary for efficient listening. Each has its own particular advantages one is incomplete without the other.

Sonic gear is useful for picking up targets at great distances because sonic sounds travel farther. Also, on the JP gear sounds appear more natural and are more easily recognized. Therefore, you can identify not only the machinery noises of enemy ships, but also any telltale noises your own submarine is making.

Supersonic gear is useful for picking up the important supersonic noises that sonic cannot get. Supersonic gear is especially superior for catching the bursts of supersonic sound used by enemy escort vessels in searching for our submarines. (In addition, QB and QC gear can be used to send out sounds into the water to determine the range of an enemy ship.)

The WCA Installation

The WCA Installation on a submarine includes all the sonar gear that handles supersonic sounds. Much of this equipment is grouped in the conning tower, where it is known as the "WCA Stack." To locate all the various units, let us subdivide WCA into its two main parts:

QB Gear has its receiver-amplifier and remote-control unit in the conning tower. The projector is mounted on the starboard shaft and extends just below the keel under the forward torpedo room. The electric training mechanism for turning the projector is in the forward torpedo room.

JK/QC Gear also has its receiver-amplifier and remote-control unit in the conning tower, and its training mechanism in the forward torpedo room. The double-faced projector extends just below the keel on the port side, opposite the QB projector. A range indicator, used with either QB or QC, is also part of the WCA stack in the conning tower.

NOTE: The WCA Installation also includes NM gear (in the control room), which is used for determining the depth of the water beneath the keel.


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