Need for Sonar Training and Testing
More than 300 extremely quiet diesel-electric 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 Navy.
Navy anti-submarine warfare training and testing activities include the use of active and passive sonar systems and small explosives charges (used as sound sources), which prepare and equip Sailors for countering threats. The development of anti-submarine detection and weapons systems is also a priority for the United States.
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 Sailors in real-life combat situations. This training cannot be duplicated with simulators or other artificial means.
Sonar Systems Testing
Scientific research, acquisition, maintenance and repair require pierside and at-sea testing to deliver combat-ready systems to naval forces. Some of the systems that require testing are sonar systems. Conducting scientific research on new sonar technology and existing sonar systems, and acquiring new systems and maintaining current systems are necessary to equip and maintain combat-ready forces capable of winning wars. The Southeast Alaska Acoustic Measurement Facility is the Navy's primary acoustic engineering measurement facility in the Pacific Northwest and it provides the capability to perform research, development, test and evaluation activities to determine the sources of acoustic noise, assess vulnerability and develop quieting measures.
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 does not put any sound energy in the water. Passive sonar can indicate the presence, character and movement of submarines if submarines are loud or operating at high speed. 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 against quiet, modern diesel-electric 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 (hull-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 modern, very quiet submarines. Active sonar is also effective for locating underwater mines. Although active sonar is the most effective way to detect quiet objects, such as submarines, Navy vessels use active sonar sparingly because sonar pulses can reveal a sending vessel’s location, compromising the mission and safety.
Training and Testing in a Noisy Environment
Sound levels in the ocean are not constant, vary with location and change over time. Different sources of sound contribute to the ocean’s overall noise level. Those sources include shipping, breaking waves, marine life 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, when combined with complex oceanographic features, create an extremely challenging and varied environment for sonar technicians. Such a complex environment is typically where most nations’ submarines operate today.
Sonar: Then and Now
In response to Allied shipping losses from U-boat attacks during World War I, 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, diesel-powered submarines operating on batteries and air-independent propulsion systems are extremely quiet and hard to detect in the noisy ocean environment. These modern submarines are relatively inexpensive and used by many nations around the world, posing a challenge for the Navy to locate, identify and track them.
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.
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 has a longer detection range that is needed for Sailors to detect a submarine before it is close enough to attack.
Training and Testing with Explosives
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 live ordnance and explosives, provides an opportunity for Sailors 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 and testing with explosives significantly enhances the safety of U.S. forces by improving combat readiness, equipment reliability and personal safety. Testing with explosives is necessary to fully test the effectiveness of devices, such as mines or mine countermeasures. To the extent possible, simulators and other available technologies are used when training and testing. Simulation, however, cannot completely replace training and testing in a real-world environment. Limited training and testing with explosives occur only in established operating areas.