1. Abhas mahawar
EN 0936121001
rrimt,lucknow

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

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.

16. APPLICATIONs
 Acoustics release
 Acoustics Fish Tags
 Echo Sounder

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.