(Acoustic homing) is the process in which a system uses the sound or acoustic signals of a target or destination to guide a moving object. There are two types of acoustic homing: passive acoustic homing and active acoustic homing. Objects using passive acoustic homing rely on detecting acoustic emissions produced by the target. Conversely, objects using active acoustic homing make use of sonar to emit a signal and detect its reflection off the target. The signal detected is then processed by the system to determine the proper response for the object. Acoustic homing is useful for applications where other forms of navigation and tracking can be ineffective. It is commonly used in environments where radio or GPS signals can not be detected, such as underwater.
The idea of using sound for navigation and homing dates back centuries and has been developed over time, so the concept of acoustic homing can not be attributed to a single individual.
Certain animals have always used sound-based navigation to survive. Bats and dolphins both use echolocation to locate prey. These animals emit sound signals and listen to the echoes for navigation and hunting purposes.
One of the earliest recorded human instances of using sound for underwater navigation was the use of a sounding lead. [1] Sailors would lower a weighted line with a lead weight attached to the end of it. By listening to the sound it made when it hit the seafloor, they were able to estimate the water's depth and the nature of the seabed.
In the 18th century, foghorns [2] were developed to aid navigation for ships in low visibility conditions caused by fog. Foghorns produced loud and low frequency sounds that traveled over long distances. The sounds helped boats identify lighthouses and other locations as well as avoid hazards.
In the early 19th century, scientists and inventors such as Charles Babbage [3] and Samuel Morse [4] experimented with underwater signaling systems. These experiments involved using bells and other sound signals to communicate with objects submerged under the water. Through these efforts, the foundation for modern underwater acoustics and sonar technology was laid out.
In the early 20th century, a Canadian inventor Reginald Fessenden [5] developed what many believe to be the first practical underwater acoustic communication system. He used sound waves to transmit messages underwater.
In World War II, acoustic homing was used by both the United States Navy and the Germans to develop acoustic torpedoes [6] to counter enemy submarines. Early versions used hydrophones to detect and navigate the torpedo to the noise of the submarine.
In the mid 20th century, sonobuoys [7] were developed for antisubmarine warfare. Sonobuoys were small floating devices dropped by aircraft which detected underwater sounds and transmitted information back to the sender.
An object can be equipped with two or more acoustic transducers, which function as speakers and microphones. If a transducer receives a sound louder than that received by the other transducer, the object turns in the transducer's direction. If the object is to maneuver in three-dimensional space, more than two transducers are needed. Typically, more than three transducers are used, and arrays of over 100 are not unknown. A large number of transducers allows for more accurate steering.
Below is a simplified method of the process of acoustic homing:
Definition: Active acoustic homing is a guidance method where the system emits its own acoustic signals and receives return echoes to locate and track a specified target. The system actively transmits sound waves and receives echoes from the target which it then processed.
Sensing method: Active acoustic homing systems use transducers or hydrophones which function as both sound transmitters and receivers. The transducers/hydrophones emit sound waves, and the sensors in the transducers/hydrophones detect the echoes from the target.
Strengths: Active acoustic homing is effective at identifying and tracking targets when the target responds to active acoustic signals. It provides precision in tracking and locating targets.
Limitations: Active acoustic signals can be detected by the target, potentially giving away the position of the homing system. It is also susceptible to countermeasures such as noisemakers and decoys.
Uses: Active acoustic homing is commonly used in anti-submarine warfare, where it is used to locate and engage submarines by pinging them with sound signals.
Definition: Passive acoustic homing is a guidance method that does not actively emit acoustic signals but rather relies on detecting acoustic emissions of the target. It listens for acoustic sounds that are naturally generated by the target.
Sensing method: Passive acoustic homing systems use hydrophones or microphones to detect and analyze sounds emitted from the target. It may be designed to listen for certain types of sounds to the exclusion of others.
Strengths: Passive acoustic homing does not emit signals of its own and is therefore less detectable by the target. It is effective in tracking acoustic targets that produce sound, even in noisy environments.
Limitations: Passive acoustic homing may have difficulties detecting silent targets or targets using stealth technology to reduce acoustic emissions. It also may have reduced accuracy in challenging conditions.
Uses: Passive acoustic homing is commonly used in underwater surveillance and marine research.
Acoustic homing can be used in:
Sonar Systems: Acoustic homing is used in many underwater sonar systems such as on submarines, ships, and fish finders. These systems use sound waves to detect underwater objects, as well as measuring the object's distance and determining the object's relative position.
Guided Missiles: Some guided missiles, such as acoustic torpedoes, use acoustic homing to detect and home in on the sound generated by a specified target, such as an aircraft engine or ship's propellers. [10]
Search and Rescue: Acoustic homing is sometimes used in search and rescue operations [11] to locate distress signals. Some examples of these
distress signals include emergency beacons and devices carried by people stranded at sea or in remote areas.
Vehicle Navigation: [12] Many autonomous underwater vehicles(AUVs) and underwater drones use acoustic homing to navigate as well as locate underwater features or waypoints. Autonomous surface vehicles(ASVs) can also use acoustic homing to navigate.
Wildlife Tracking: Scientists use acoustic homing to monitor and study wildlife in natural habitats. This is done by attaching acoustic transmitters to animals and then using receivers to monitor it's movements and behavior.
Mines Detection: [13] Acoustic homing can be used to detect and avoid buried antitank mines during warfare.
Mines: Some underwater mines also make use of acoustic homing, where the mines would be triggered and detonate after detecting passing ships or submarines.
Sonar is a technique that uses sound propagation to navigate, measure distances (ranging), communicate with or detect objects on or under the surface of the water, such as other vessels.
A hydrophone is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates an electric potential when subjected to a pressure change, such as a sound wave.
A sonobuoy is a relatively small buoy – typically 13 cm (5 in) diameter and 91 cm (3 ft) long – expendable sonar system that is dropped/ejected from aircraft or ships conducting anti-submarine warfare or underwater acoustic research.
An anti-submarine weapon (ASW) is any one of a number of devices that are intended to act against a submarine and its crew, to destroy (sink) the vessel or reduce its capability as a weapon of war. In its simplest sense, an anti-submarine weapon is usually a projectile, missile or bomb that is optimized to destroy submarines.
An acoustic torpedo is a torpedo that aims itself by listening for characteristic sounds of its target or by searching for it using sonar. Acoustic torpedoes are usually designed for medium-range use, and often fired from a submarine.
The Mark 24 mine is an air-dropped anti-submarine (ASW) acoustic torpedo developed by the United States during World War II; it was called a mine to conceal its capabilities. The torpedo entered service with the Allies in March 1943; the United States Navy (USN) used it until 1948. Approximately 4,000 were produced. Of the 340 deployed during the war, 204 were fired, sinking 37 and damaging 18 Axis submarines.
A towed array sonar is a system of hydrophones towed behind a submarine or a surface ship on a cable. Trailing the hydrophones behind the vessel, on a cable that can be kilometers long, keeps the array's sensors away from the ship's own noise sources, greatly improving its signal-to-noise ratio, and hence the effectiveness of detecting and tracking faint contacts, such as quiet, low noise-emitting submarine threats, or seismic signals.
Anti-submarine warfare is a branch of underwater warfare that uses surface warships, aircraft, submarines, or other platforms, to find, track, and deter, damage, or destroy enemy submarines. Such operations are typically carried out to protect friendly shipping and coastal facilities from submarine attacks and to overcome blockades.
Acoustic location is a method of determining the position of an object or sound source by using sound waves. Location can take place in gases, liquids, and in solids.
The term acoustic signature is used to describe a combination of acoustic emissions of sound emitters, such as those of ships and submarines. In addition, aircraft, machinery, and living animals can be described as having their own characteristic acoustic signatures or sound attributes, which can be used to study their condition, behavior, and physical location.
Ultrasonic transducers and ultrasonic sensors are devices that generate or sense ultrasound energy. They can be divided into three broad categories: transmitters, receivers and transceivers. Transmitters convert electrical signals into ultrasound, receivers convert ultrasound into electrical signals, and transceivers can both transmit and receive ultrasound.
Geophysical MASINT is a branch of Measurement and Signature Intelligence (MASINT) that involves phenomena transmitted through the earth and manmade structures including emitted or reflected sounds, pressure waves, vibrations, and magnetic field or ionosphere disturbances.
Bistatic sonar is a sonar configuration in which transmitter and receiver are separated by a distance large enough to be comparable to the distance to the target. Most sonar systems are monostatic, in that the transmitter and receiver are located in the same place. A configuration with multiple receivers is called multistatic.
GPS sonobuoy or GPS intelligent buoy (GIB) are a type of inverted long-baseline (LBL) acoustic positioning devices where the transducers are installed on GPS-equipped sonobuoys that are either drifting or moored. GIBs may be used in conjunction with an active underwater device, or with a passive acoustic sound source. Typically the sound source or impact event is tracked or localized using a time of arrival (TOA) technique. Typically several GIBs are deployed over a given area of operation; with the total number determined by the size of the test area and the accuracy of the results desired. Different methods of GPS positioning may be used for positioning the array of GIBs, with accuracies of cm to meter level in realtime possible.
A Fessenden oscillator is an electro-acoustic transducer invented by Reginald Fessenden, with development starting in 1912 at the Submarine Signal Company of Boston. It was the first successful acoustical echo ranging device. Similar in operating principle to a dynamic voice coil loudspeaker, it was an early kind of transducer, capable of creating underwater sounds and of picking up their echoes.
Underwater searches are procedures to find a known or suspected target object or objects in a specified search area under water. They may be carried out underwater by divers, manned submersibles, remotely operated underwater vehicles, or autonomous underwater vehicles, or from the surface by other agents, including surface vessels, aircraft and cadaver dogs.
The AN/AQS-13 series was a helicopter dipping sonar system for the United States Navy. These systems were deployed as the primary inner zone anti-submarine warfare (ASW) sensor on aircraft carrier based helicopters for over five decades. Companion versions with the AQS-18 designation were exported to various nations around the globe.
Radio acoustic ranging, occasionally written as "radio-acoustic ranging" and sometimes abbreviated RAR, was a method for determining a ship's precise location at sea by detonating an explosive charge underwater near the ship, detecting the arrival of the underwater sound waves at remote locations, and radioing the time of arrival of the sound waves at the remote stations to the ship, allowing the ship's crew to use true range multilateration to determine the ship's position. Developed by the United States Coast and Geodetic Survey in 1923 and 1924 for use in accurately fixing the position of survey ships during hydrographic survey operations, it was the first navigation technique in human history other than dead reckoning that did not require visual observation of a landmark, marker, light, or celestial body, and the first non-visual means to provide precise positions. First employed operationally in 1924, radio acoustic ranging remained in use until 1944, when new radio navigation techniques developed during World War II rendered it obsolete.
Submarine signals had a specific, even proprietary, meaning in the early 20th century. It applied to a navigation aid system developed, patented and produced by the Submarine Signal Company of Boston. The company produced submarine acoustic signals, first bells and receivers then transducers, as aids to navigation. The signals were fixed, associated with lights and other fixed aids, or installed aboard ships enabling warning of fixed hazards or signaling between ships. ATLAS-Werke, at the time Norddeutsche Maschinen und Armaturenfabrik, of Germany also manufactured the equipment under license largely for the European market.
Low Frequency Analyzer and Recorder and Low Frequency Analysis and Recording (LOFAR) are the equipment and process respectively for presenting a visual spectrum representation of low frequency sounds in a time–frequency analysis. The process was originally applied to fixed surveillance passive antisubmarine sonar systems and later to sonobuoy and other systems. Originally the analysis was electromechanical and the display was produced on electrostatic recording paper, a Lofargram, with stronger frequencies presented as lines against background noise. The analysis migrated to digital and both analysis and display were digital after a major system consolidation into centralized processing centers during the 1990s.