Acoustic location

Acoustic location

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Acoustic location is the science of using sound
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...

 to determine the distance and direction of something. Location can be done actively or passively, and can take place in gases (such as the atmosphere), liquids (such as water), and in solids (such as in the earth).
  • Active acoustic location involves the creation of sound in order to produce an echo, which is then analyzed to determine the location of the object in question.

  • Passive acoustic location involves the detection of sound or vibration created by the object being detected, which is then analyzed to determine the location of the object in question. (See Sound ranging
    Sound ranging
    In land warfare, sound ranging is a method of determining the coordinates of a hostile artillery battery using data derived from the sound of its guns firing...

    )


Both of these techniques, when used in water, are known as sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

; passive sonar and active sonar are both widely used.

Acoustic mirrors and dishes, when using microphones, are a means of passive acoustic localization, but when using speakers are a means of active localization. Typically, more than one device is used, and the location is then triangulated between the several devices.

Acoustic location in air was used from mid-World War I to the early years of World War II for the passive detection of aircraft by picking up the noise of the engines. It was rendered obsolete before and during World War II by the introduction of radar, which was far more effective but interceptable. Acoustics has the advantage that it can see around corners and over hills.

Active / passive locators


Active locators have some sort of signal generation device, in addition to a listening device. The two devices do not have to be located together.

Sonar


SONAR (SOund Navigation And Ranging) — or sonar — is a technique that uses sound propagation under water (or occasionally in air) to navigate, communicate or to detect other vessels. There are two kinds of sonar — active and passive. A single active sonar can localize in range and bearing as well as measuring radial speed. However, a single passive sonar can only localize in bearing directly, though target motion analysis can be used to localize in range, given time. Multiple passive sonars can be used for range localization by triangulation or correlation, directly.

For more information on this item, see the article on Sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

.

Biological echo location


Dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...

s, whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...

s and bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...

s use echolocation
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...

 to detect prey and avoid obstacles.

Time-of-arrival localization


Having speakers/ultrasonic
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...

 transmitters emitting sound at known positions and time, the position of a target equipped with a microphone/ultrasonic receiver can be estimated based on the time of arrival
Time of arrival
Time of arrival , also called time of flight , is the travel time of a radio signal from a single transmitter to a remote single receiver. By the relation between light speed in vacuum and the carrier frequency of a signal the time is a measure for the distance between transmitter and receiver...

 of the sound. The accuracy is usually poor under non-line-of-sight conditions, where there are blockages in between the transmitters and the receivers

.

Seismic surveys


Seismic surveys involve the generation of sound waves to measure underground structures. Source waves are generally generated by percussion mechanisms located near the ground or water surface, typically dropped weights, vibroseis trucks, or explosives. Data are collected with geophones, then stored and processed by computer. Current technology allows the generation of 3D images of underground rock structures using such equipment.

For more information, see Reflection seismology
Reflection seismology
Reflection seismology is a method of exploration geophysics that uses the principles of seismology to estimate the properties of the Earth's subsurface from reflected seismic waves. The method requires a controlled seismic source of energy, such as dynamite/Tovex, a specialized air gun or a...

.

Ecotracer


Ecotracer is an acoustic locator that was used to determining the presence and position of ships in fog. Some could detect targets at distances up to 12 kilometers. Static walls could detect aircraft up to 30 miles away.

Types


There were three main kinds of system:
  • Personal/wearable horns
  • Transportable steerable horns
  • Static dishes
  • Static walls

Impact


American acoustic locators were used in 1941 to detect the Japanese attack on the fortress island of Corregidor
Corregidor
Corregidor Island, locally called Isla ng Corregidor, is a lofty island located at the entrance of Manila Bay in southwestern part of Luzon Island in the Philippines. Due to this location, Corregidor was fortified with several coastal artillery and ammunition magazines to defend the entrance of...

 in the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...

.

See also

  • Acoustic mirror
    Acoustic mirror
    An acoustic mirror is a passive device used to reflect and perhaps to focus sound waves.- Overview :Prior to World War II and the invention of radar, acoustic mirrors were built as early warning devices around the coasts of Great Britain, with the aim of detecting airborne invasions...

  • Animal echolocation
    Animal echolocation
    Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...

    : animals emitting sound
    Sound
    Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...

     waves and listening to the echo in order to locate objects or navigate.
  • Human echolocation
    Human echolocation
    Human echolocation is the ability of humans to detect objects in their environment by sensing echoes from those objects. By actively creating sounds – for example, by tapping their canes, lightly stomping their foot or making clicking noises with their mouths – people trained to orientate with...

    : the use of echolocation by blind
    Blindness
    Blindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...

     people.
  • Acoustic wayfinding
    Acoustic wayfinding
    Acoustic wayfinding is the practice of using the auditory system to orient oneself and navigate physical space. It is commonly used by the visually impaired, allowing them to retain their mobility without relying on visual cues from their environment....

    : the practice of using auditory cues and sound markers to navigate indoor and outdoor spaces.
  • Sonar
    Sonar
    Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

    : (sound navigation and ranging) the use of sound to navigate
    Navigation
    Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...

     or to locate other watercraft, usually by submarine
    Submarine
    A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

    s.
  • Echo sounding
    Echo sounding
    Echo sounding is the technique of using sound pulses directed from the surface or from a submarine vertically down to measure the distance to the bottom by means of sound waves. This information is then typically used for navigation purposes or in order to obtain depths for charting purposes...

    : listening to the echo of sound pulses to measure the distance to the bottom of the sea, a special case of Sonar.
  • Medical ultrasonography
    Medical ultrasonography
    Diagnostic sonography is an ultrasound-based diagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions...

    : the use of ultrasound
    Ultrasound
    Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...

     echoes to look inside the body.
  • Sensory substitution
    Sensory substitution
    Sensory substitution means to transform the characteristics of one sensory modality into stimuli of another sensory modality. It is hoped that sensory substitution systems can help handicapped people by restoring their ability to perceive a certain defective sensory modality by using sensory...

  • Japanese war tuba
    Japanese War Tuba
    The Japanese war tuba is a colloquial name sometimes applied to Imperial Japanese Army acoustic locators due to the visual resemblance to the musical tuba...

    : 1930's Japanese acoustic locator.
  • Sound localisation

External links