Abhas hydrophone
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Transcript of Abhas hydrophone
HYDROPHONE
Abhas mahawarEN 0936121001rrimt,lucknow
Overview
• Introduction and History• Working Principle• Piezoelectric Effect• Practical Implementation• Applications• Advantages & Disadvantages• Hydrophone vs. Sonar• Conclusion
Hydrophone?
Hydrophone (Greek
"hydro" = "water" and "phone" = "sound") is a microphone designed to be used underwater for recording or listening to underwater sound.
A "Hydrophone" is a device which will listen to, or pick up, the acoustic energy underwater, converts acoustic energy into electrical energy.
Hydrophones are usually used below their resonance frequency.
Most Hydrophones are based on a piezoelectric transducer that generates electricity when subjected to a pressure changes underwater.
History Hydrophone was used late in World War I. Naval Forces
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.
How does it Work?Hydrophone device that receives
underwater sound waves and converts them to electrical energy.
There are special computer programs that
analyze these signals.
Further these signal can be read on a meter or played through a loudspeaker
PrincipleThe basic working principle is the
piezoelectric effect.
Hydrophones are being embedded with these piezoelectric transducers.
These transducer converts changes in water pressure into an electrical form.
Piezoelectric EffectThe conversion of mechanical
vibrations into electrical energy and vice-versa.
The active element is basically a piece of polarized material.
Affecting FactorThe factors affecting the working is acoustic impedance.
Acoustic impedance ( sound impedance) is a frequency dependent parameter.
Mathematically,
p denotes ‘sound pressure’.v denotes ‘particle velocity’.s denotes ‘surface area’.
Types of Hydrophones
Hydrophones are generally of two types
OMNIDIRECTIONAL HYDROPHONES which records sounds from all directions with equal sensitivity.
DIRECTIONAL HYDROPHONES which have a higher sensitivity to signals from a particular direction.
OMNIDIRECTIONAL HYDROPHONE
Omnidirectional Hydrophones BII-7000 are generally used in underwater vehicles AUV/UUVS & ROVS
Directional Hydrophones
FocusedIn this the hydrophone is held in a particular direction. To increase its sensitivity the receiving end must be spherical.
Arrayed HydrophoneIn this number of hydrophones are connected together to a single display unit. This pattern increases the efficiency.
Practical Implementation
Widely used in submarines and ships.
Helpful for naval defense services.
Detection of different sound wave frequencies.
APPLICATIONs
Acoustics release
Acoustics Fish Tags
Echo Sounder
AdvantageHydrophones does not require a power
source as they convert mechanical energy into electrical energy. Although other devices such as underwater cameras need a power source.
Underwater cameras are not as accurate as hydrophones because underwater cameras must be kept in an air-tight container
Disadvantages
Hydrophones can only listen to sounds and pressure differences.
Hydrophones are limited in their ability to distinguish between multiple objects or natural phenomenon and artificial noise
Set up requires time and space.
Comparison
Hydrophone is generally a unidirectional device while sonar is an omnidirectional device.
Not all hydrophones work as emitter but sonar works as a receiver and transmitter.
ConclusionThe technique is based on
piezoelectric effect.
A unidirectional device that can be further improved.
The technique can only be used in denser fluid because of the acoustic impedance matching.
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