GOA Admin

More than 300 extremely quiet, modern submarines are operated by more than 40 nations worldwide, and these numbers are growing. These quiet, difficult-to-detect submarines, as well as in-water mines and torpedoes, are threats to global commerce, national security, and the safety of military personnel. As a result, anti-submarine warfare is a top war-fighting and training priority for the United States (U.S.) Department of the Navy (Navy).

Navy anti-submarine warfare training activities include the use of active and passive sonar systems and small explosives charges (used as sound sources), which prepare and equip service members for countering threats. The development of anti-submarine detection and weapons systems is also a priority for the Navy.

Sonar proficiency is a complex and difficult skill that requires constant training in realistic conditions at sea. Lack of realistic training could jeopardize the lives of service members in real-life combat situations. This training cannot be duplicated with simulators or other artificial means.

What is Sonar?

Sonar, an acronym for SOund NAvigation and Ranging, uses sound energy waves to detect and locate submerged objects, such as submarines and mines. There are two types of sonar:

Passive sonar is a sound-receiving system that “listens” for sound waves generated by man-made or biological sources using underwater microphones that receive, amplify, and process underwater sounds. Passive sonar is less capable than active sonar of detecting quiet submarines operating in areas where background noise levels are elevated, such as coastal waters. Although improvements in passive sonar are continually being researched, passive sonar currently is less effective than active sonar at detecting modern, quiet submarines.

Active sonar is the most effective means available for locating objects underwater. Active sonar sends out a pulse of energy, often called a “ping,” that travels through water, reflects off an object, and returns to a receiver on the ship. Skilled technicians can use the reflected sonar pulse to determine the range, distance, and movement of an object. Common active sonars include echo sounders (such as depth sounders and fish finders), side-scan sonars, and military sonars (ship-mounted and/or sonobuoys).

Active sonar has the ability to locate objects that are too quiet to be detected using passive sonar technology. This makes active sonar invaluable for detecting very quiet submarines. Active sonar is also effective for locating underwater mines. Although active sonar is the most effective way to detect quiet objects, Navy vessels use active sonar sparingly because sonar pulses can reveal a sending vessel’s location, compromising the mission and safety.

Sound levels in the ocean are not constant, varying with location and time. Many sources contribute to the ocean’s overall noise level. Those sources include shipping, mineral extraction, fishing, recreational boating, breaking waves, marine life, storm events, and other man-made and natural sounds.

The ocean is generally noisier in coastal areas, where many natural and man-made sounds exist. Coastal waters present a complex environment of varying depths, coastal boundaries, tides and currents, weather patterns, and significant biological and commercial activities.

Coastal waters contain 80 percent of all ocean life and support many human activities, including commercial shipping ports, fishing fleets, and oil exploration and drilling. These activities bring significant noise to the coastal environment, and combined with complex oceanographic features, create an extremely challenging and varied environment for sonar technicians. This complex coastal environment is typically where most nations’ submarines operate today.

In response to devastating Allied shipping and human losses from U-boat attacks during World War II, the Navy began using sonar to locate submerged objects. Today, sonar is used not only to identify, track, and target submarines, but also to determine water depth and locate underwater mines. With advances in warfare technology, submarines operating on batteries and air-independent propulsion systems are extremely quiet and hard to detect in the noisy ocean environment. These submarines are relatively inexpensive and used by many nations around the world, posing a challenge for the Navy to locate, identify, and track them.

Sonar Today

Present Day

Modern, quiet submarines can approach close enough to deploy long-range weapons before entering the passive sonar detection range of U.S. vessels. Active sonar’s longer detection range is needed for service members to detect a submarine before it is close enough to attack.

Sonar Then

Then – 1970s

Submarines of the previous generation were noisy and could be detected with passive sonar before they came close enough to deploy short-range weapons against a vessel.

The Navy currently trains with explosives primarily within established operating areas, and would continue to do so under the Proposed Action. Training with explosives under real-life conditions is necessary for the readiness of military personnel who may be called to respond to emergencies and national security threats. Operating in a high-stress environment, including the use of and exposure to high-explosive ordnance and explosives for such activities as detonating enemy mines, provides an opportunity for service members to practice the critical tasks and coordination essential to survival and success. Practicing these skills is necessary to ensure accuracy and instill confidence in military personnel.

Training with explosives significantly enhances the safety of U.S. forces by improving combat readiness, equipment reliability, and personal safety. To the extent possible, simulators and other available technologies are used when training. Simulation, however, cannot completely replace realistic training.