2. Overview
• Introduction and History
• Working Principle
• Piezoelectric Effect
• Practical Implementation
• Applications
• Advantages & Disadvantages
• Hydrophone vs. Sonar
• Conclusion
3. Hydrophone?
Hydrophone (Greek
"hydro" = "water" and "phone"
= "sound") is a microphone
designed to be used
underwater for recording or
listening to underwater sound.
4. A "Hydrophone" is a device which will listen to, or
pick up, the acoustic energy underwater, converts
acoustic energy into electrical energy.
Most Hydrophones are based on a
piezoelectric transducer that generates
electricity when subjected to a pressure
changes underwater.
Hydrophones are usually used below
their resonance frequency.
5. 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.
6. 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
7.
8. Principle
The 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.
9. Piezoelectric Effect
The conversion of mechanical vibrations
into electrical energy and vice-versa.
The active element is basically a piece of
polarized material.
10. Affecting Factor
The 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’.
11. 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.
12. OMNIDIRECTIONAL
HYDROPHONE
Omnidirectional Hydrophones BII-7000 are
generally used in underwater vehicles
AUV/UUVS & ROVS
13. Directional Hydrophones
Focused
In this the hydrophone is held in a particular
direction. To increase its sensitivity the
receiving end must be spherical.
14. Arrayed Hydrophone
In this number of hydrophones are connected
together to a single display unit. This pattern
increases the efficiency.
15. Practical
Implementation
Widely used in submarines and ships.
Helpful for naval defense services.
Detection of different sound wave
frequencies.
17. Advantage
Hydrophones 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
18. 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.
19. 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.
20. Conclusion
The 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.
