A hydrophone (Greek "hydro" = "water" and "phone" = "sound") is a
microphonedesigned to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducerthat generates electricity when subjected to a pressure change. Such piezoelectric materials, or transducers can convert a sound signal into an electrical signal since soundis a pressure wave in fluids. Some transducers can also serve as a projector ( emitter), but not all have this capability, and may be destroyed if used in such a manner.
A hydrophone can "listen" to sound in air, but will be less sensitive due to its design as having a good
acoustic impedancematch to water, the denser fluid. Likewise, a microphone can be buried in the ground, or immersed in water if is put in a waterproof container, but will give similarly poor performance due to the similarly bad acoustic impedance match.
The hydrophone was used late in
World War I. Convoyescorts used them to detect U-boats, greatly lessening the effectiveness of the submarine. Ernest Rutherford, in England, led pioneer research in hydrophones using piezoelectric devices. His only patent was for a hydrophone device.
From late in World War One until the introduction of active
sonar, hydrophones were the sole method for submarines to detect targets while submerged, and remain useful today.
A small single cylindrical ceramic
transducercan achieve near perfect omnidirectional reception. Directional hydrophones increase sensitivity from one direction using two basic techniques:
This device uses a single
transducerelement with a dish or conical-shaped sound reflector to focus the signals, in a similar manner to a reflecting telescope. This type of hydrophone can be produced from a low-cost omnidirectional type, but must be used while stationary, as the reflector impedes its movement through water.
Multiple hydrophones can be arranged in an
arrayso that it will add the signals from the desired direction while subtracting signals from other directions. The array may be steered using a beamformer. Most commonly, hydrophones are arranged in a "line array"Fact|date=October 2007 but may be in two or three dimensional arrangements.
Communication with submarines
* Pike, John (1999).
SOSUSRetrieved Jan. 28, 2005.
* Watlington, Frank (1979). "How to build & use low-cost hydrophones." (ISBN 0830610790)
* Unknown. [http://www.ob-ultrasound.net/hydrophone.html hydrophone] Retrieved Jan. 28, 2005.
* Unknown. (2005) [http://www.glossary.oilfield.slb.com/Display.cfm?Term=hydrophone Schlumberger Oilfield Glossary: Term 'hydrophone'] Retrieved Jan. 28, 2005.
* [http://dosits.org/science/measurng/1.htm DOSITS ] Hydrophone introduction at Discovery of Sound in the Sea
* [http://orcasound.net?07enohpordyhikiw10 orcasound.net ] Live hydrophone streams from killer whale habitat
* [http://pamguard.org Passive Acoustic Monitoring ] Using hydrophones to monitor underwater sounds
* [http://sonar-fs.lboro.ac.uk/uag/products/products_hydrophone.html Build your own hydrophone ] (free instructions)
* [http://freesound.iua.upf.edu/forum/viewtopic.php?p=13253 Build your own hydrophone #2] Online tutorial at the freesound project.
* [http://freesound.iua.upf.edu/packsViewSingle.php?id=2885 Hydrophone recordings] at the freesound project.
* [http://acoustics.co.uk/ Precision Acoustics] useful resource on hydrophones
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Look at other dictionaries:
hydrophone — [ idrɔfɔn ] n. m. • mil. XXe; de hydro et phone ♦ Techn. Transducteur électroacoustique utilisé pour l émission et la réception d ondes acoustiques dans l eau, que l on emploie en sismologie, dans la détection pétrolière, etc. ● hydrophone nom… … Encyclopédie Universelle
hydrophone — [hī′drə fōn΄] n. [ HYDRO + PHONE] an instrument for detecting, and registering the distance and direction of, sound transmitted through water … English World dictionary
Hydrophone — Un hydrophone est un transducteur électroacoustique destiné à transformer, dans les liquides, des oscillations acoustiques en oscillations électriques. Ce type de transducteur est notamment utilisé dans les sonar. Exemple de modèle d hydrophone… … Wikipédia en Français
hydrophone — noun Date: 1860 an instrument for listening to sound transmitted through water … New Collegiate Dictionary
hydrophone — an underwater microphone … Dictionary of ichthyology
hydrophone — /huy dreuh fohn /, n. 1. a device for locating sources of sound under water, as for detecting submarines by the noise of their engines. 2. an instrument employing the principles of the microphone, used to detect the flow of water through a pipe.… … Universalium
hydrophone — noun a transducer that converts underwater sound waves into electrical signals, rather like a microphone … Wiktionary
hydrophone — n. instrument that determines direction and distance of sound underwater … English contemporary dictionary
hydrophone — noun a microphone which detects sound waves under water … English new terms dictionary
hydrophone — hy·dro·phone … English syllables