Acoustic location is the art and science of using
soundSound is a travelling wave which 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.- Perception of sound...
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 analysed 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 analysed to determine the location of the object in question.
Both of these techniques, when used in water, are known as
sonarSonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels. There are two kinds of sonar: active and passive. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water...
; passive sonar and active sonar are both widely used.
Acoustic mirrors and dishes, when using microphones, are a means of passive acoustic localisation, but when using speakers are a means of active localisation.
Acoustic location is the art and science of using
soundSound is a travelling wave which 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.- Perception of sound...
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 analysed 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 analysed to determine the location of the object in question.
Both of these techniques, when used in water, are known as
sonarSonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels. There are two kinds of sonar: active and passive. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water...
; passive sonar and active sonar are both widely used.
Acoustic mirrors and dishes, when using microphones, are a means of passive acoustic localisation, but when using speakers are a means of active localisation. 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-WWI to the early years of WWII for the passive detection of aircraft by picking up the noise of the engines. It was rendered obsolete before and during WWII 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 - the former often being used for active localisation and the latter often for passive localisation. An single active sonar can localise in range and bearing as well as measuring radial speed. However, a single passive sonar can only localise in bearing directly, though target motion analysis can be used to localise in range, given time. Multiple passive sonars can be used for range localisation by triangularisation or correlation, directly.
For more information on this item, see the article on
SonarSonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels. There are two kinds of sonar: active and passive. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water...
.
Biological echo location
DolphinsDolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in seventeen 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...
,
whalesWhale is the common name for marine mammals of the order Cetacea. The term whale is sometimes used to refer to all cetaceans, but in more common English usage it generally excludes the members of the Delphinoidea superfamily, such as dolphins and porpoises...
and
batsBats are flying mammals in the order Chiroptera . The forelimbs of bats are webbed and developed as 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...
use
echolocationEcholocation, also called biosonar, is the biological sonar used by several animals such as dolphins, shrews, most bats, and most whales. The term was coined by Donald Griffin, who was the first to conclusively demonstrate its existence in bats...
to detect prey and avoid obstacles.
Time-of-arrival localization
Having speakers/ultrasonic 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 arrivalTime of Arrival , also named Time of flight , which both means 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...
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 seismologyReflection 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...
.
See also
- Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several animals such as dolphins, shrews, most bats, and most whales. The term was coined by Donald Griffin, who was the first to conclusively demonstrate its existence in bats...
: animals emitting soundSound is a travelling wave which 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.- Perception of sound...
waves and listening to the echo in order to locate objects or navigate.
- Human echolocation
Human echolocation is the ability of humans to sense objects in their environment by hearing echoes from those objects. This ability is used by some blind people to navigate within their environment. They actively create sounds, such as by tapping their canes or by making clicking noises with...
: the use of sound by blindBlindness 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 to navigate.
- Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels. There are two kinds of sonar: active and passive. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water...
: (sound navigation and ranging) the use of sound to navigateNavigation is the process of reading, 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. The word navigate is derived from the Latin "navigare", meaning "to sail"...
or to locate other watercraft, usually by submarineA submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has only limited underwater capability...
s.
- 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. Echo sounding can also refer to hydroacoustic "echo sounders" defined as active sound in water used to study fish...
: listening to the echo of sound pulses to measure the distance to the bottom of the sea, a special case of Sonar.
- Medical ultrasonography
Diagnostic sonography is an ultrasound-based diagnostic imaging technique used to visualize subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions. Obstetric sonography is commonly used during pregnancy and is widely...
: the use of ultrasoundUltrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Although this limit varies from person to person, it is approximately 20 kilohertz in healthy, young adults and thus, 20 kHz serves as a useful lower limit in describing ultrasound...
echoes to look inside the body.
- 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
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.