By: Casey Repasy, Brenton Pedersen, Kevin

McGraw, Kelsey Zdebski, and Athena Grele

The Impact of Sonar

FIRST OF ALL. .WHAT IS SONAR?

Sonar, which was in itself originally an acronym for SOund Navigation

And Ranging, is by definition “A method of detecting, locating, and

determining the speed of objects through the use of reflected sound

waves. A sound signal is produced, and the time it takes for the signal to

reach an object and for its echo to return is used to calculate the object's

distance…A system using transmitted and reflected underwater sound

waves to detect and locate submerged objects or measure the distance to

the floor of a body of water.”

It can also be referred to as echolocation, and is essentially used to

navigate, communicate with, and detect other vessels

BEFORE SONAR…

Before sonar the only technology people used was to actually

listen to the water with different devices

For example, Leonardo Da Vinci was said to have placed a

tube in the water, and held his ear up to it to attempt to detect

vessels in 1490• This technology (sonar) was widely impractical and seen as

more of a novelty then a real science.• The technology was not around because there was no use for it

yet.• The technology grew interest in WWI because they needed a

way to detect enemy submarines.

THE DEVELOPMENT OF SONAR

Underwater acoustics was built upon the principles of sound

observed prior to the 20th Century. It was the development of

transducers in the preceding century that allowed the technique of

using sound to navigate and determine the range of objects

underwater to develop into the system commonly referred to as

“sonar” (Sound, Navigation, and Ranging).

Until the harnessing of electricity there was no way to amplify

sound, since the waves attenuate and cannot be reasonably reinforced

while in motion.• However, if the sound can be translated into electrical signals via the

transmitters and receivers in a transducer array, the same frequency can be related with a higher amplitude, effectively increasing the volume of the sound.

DEVELOPMENT AND EXPLANATION CONTINUED

Little was known about the behavior of sound in water prior to transduction technology

other than that it would travel at higher speeds in a liquid medium than a gaseous one.

The first attempt to measure this speed was in 1808 by J. B. Biot, who literally timed how

long it took sound to travel through a 1000m iron water pipe in Paris. • In 1924, data detailing the dependence of sound speed on temperature, depth, and salinity

was published by Heck and Service. This data served to confirm Snell’s Law as put forth by Descartes in 1637, though Snell’s Law had only previously been applied to light.

In short, when temperature, depth, and/or salinity increases, so too does the speed of

sound, but because of Snell’s Law, the sound ray’s acceleration will slow and eventually

bend away from the effects that are causing its speed to increase. In places where the

sound can reach its maximum and minimum speeds such as the Deep Sound Channel, a

layer of the ocean labeled so because sound that breaks the surface duct in two-mile

deep waters runs the risk of becoming “trapped,” sound rays travel in an approximate

sine wave.

THE FIRST TYPES OF SONAR

In 1822 Daniel Colloden used an

underwater bell to find the

calculations of the speed of sound

underwater in Switzerland; this was a

step towards sonar

In 1906 Lewis Nixon was the first to

invent Sonar.• He invented it to detect

icebergs• The picture to the right

depicts it’s early and simple use

THE FIRST TYPES OF SONAR

The first type of sonar to detect submarines

was invented in 1915 by Paul Langevin, a

French Physicist • This was a passive device and

didn’t send out signals (he worked on the use of ultrasonic waves in submarine detection)

• However, by 1918 both US and Britain had active systems that sent out and received signals

RESULTING IMPACT OF SONAR TODAY

In the Military:• Most importantly, sonar is used for navigation: using

the sound waves that bounce back to navigate underwater.

• It is also used for Target Tracking: exactly what it sounds like; using the reflected sound waves to seek and find a target.

• Today the military would not be what it is if it were not for sonar; their sonar systems are very powerful, and the military would not have all of its knowledge of stealth and surveying that it has without them

CONTINUED IMPACT

For underwater navigation, Oceanography:• Topography: sonar is used in topography to reconstruct certain shipwreck

sites, underwater reefs, and certain depths of the ocean that humans and submarines cannot withstand.

• Animals: until sonar was discovered it was unknown how animals that dwelled in the ocean communicated with one another.

• Discoveries: many important discoveries of species as well as abnormalities in the ocean floor – trenches, forming volcanoes, and islands, etc.

In conclusion, sonar is a very important, successful discovery that has

become extremely important and necessary for military use and under

water navigation, such as oceanography and topography. Without it, our

military would be put at a great disadvantage, and we would be able to do

much less underwater

SOURCES

Rossing, Thomas D. ‘Springer Handbook of Acoustics’,

Springer Science+Business Media, New York. 2007. 11-20.

http://mainland.cctt.org/istf2006/sonar.asp

http://www.marinebuzz.com/2008/02/19/who-invented-so

nar-a-controversy

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http://www.biologycorner.com/worksheets/articles/(

article)sonar.html