History of sonar
Types of Sonar
New innovation of sonar
How it works
Sonar,which in itself originally an acronym for sound navigation &
Sonar is a device that is used to detect underwater objects
using sound waves.
In this system a sound pulse is generated and sent
underwater through a transmitter.
Sound waves are reflected by the underwater object which are
received at receiver.
The time taken by sound wave to come back is
And by knowing the speed of sound wave in water the
distance can be easily calculated by formula.
Distance = speed x time
The acoustic frequencies used in sonar systems vary
from very low (infrasonic) to extremely high (ultrasonic).
We know that some animals (dolphins and bats) have use sound as a
medium of communication and objects detection for millions of years.
But use of the sound by
humans in the water is initially
recorded by Leonardo da Vinci
in 1490: a tube inserted into
the water was said to be used
to detect vessels by placing an
ear to the tube.
Sonar was first patented by
Lewis Richardson and German
physicist Alexander Behm in
The first measurement of sound speed in 1826
Active sonar uses sound
transmitter and receiver . And
there are 3 modes of operation :
Monostatic mode : When the transmitter and receiver are at
the same place.
Bistatic mode : When the transmitter and receiver are
separated by some distance.
Multistatic mode : When more transmitters (or more
receivers) are used, again spatially separated.
Passive sonar listens without
Passive sonar has a wide variety of
techniques for identifying the source of
a detected sound.
Passive sonar system have large
sonic database but sonar operator
classify signals by use of computer
and use these databases to identify
classes of ships and action.
It is used to find the actual depth of the sea.
Sonar systems are used to find lost ships and
These are used in ocean surveillance systems.
They are used by navy detect the locations of enemy
They are used for under water security.
It has an adverse effects on marine animals like
dolphins and whales ,that also use sound waves for
It leads whales to painful and often fatal
The sonar systems generate lot of noise.
High intensity sonar sounds can create a small
temporary shift in the hearing threshold of some fish.
NEW INnovation OF SONAR
FORGET TINY MOBILES KEYBOARD YOU
COULD SOON TYPE IN MID-AIR &
A new sonar technology developed by a lead author Rajlakshmi
Nandkumar a student in University of Washington,and some
computer scientists and electrical engineers that allows you to
interact with mobile devices by writing or gesturing on any
nearby surface -- a tabletop, a sheet of paper or even in mid-air.
A new sonar technology called Finger IO will make it easier to interact
with screens on smartwatches and smartphones by simply writing or
gesturing on any nearby surface. It’s is an active sonar system using the
device’s own microphones and speakers to track fine-grained finger
movements (to within 8mm).
Two microphones are needed to track finger motion in two dimensions,
and three for three dimensions. So this system may work (when
available commercially) with some smartphones (it was tested with a
Samsung Galaxy S4).
It also track subtle finger motion around the device,even when the phone
is inside a pocket.
HOW IT WORKS
The device’s own speaker to release an inaudible
sound wave which we can’t heard.These are called
Orthogonal Frequency DivisionMultiplexing.
That signal rebounds off the finger, and those “echoes”
are recorded by the device’s microphones and helped to
estimate the finger’s current place in space.
The minimum difference between the drawings and
the FingerIO tracings was 0.8 centimetres for the
smartphone and 1.2 centimetres for the smartwatch.
The scientists developed a FingerIO prototype app
for smartphone and a smartwatch equipped with two
microphones, which are required to track finger
motion in two dimensions
It’s very easy way of typing and after sometime we
use this technique.
Finger IO makes it easier than ever to interact with
devices that have small screens.
Finger IO does not require any special finger
instrumentation, sensors or hardware.