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THE CONTENTS OF SONAR

AN OUTLINE OF THE SCIENCE AND EFFECTS OF SONAR

TYLER MCCOMAS, DALLIN BENSON, JUSTINE WHIMPEY,

LICHELLE COOKE, and AJ JOHNSON

SALT LAKE COMMUNITY COLLEGE PHYSICS 1010

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TABLE OF CONTENTS

INTRODUCTION OF SONAR..........................................................................................................................2

CHAPTER 1-ACTIVE AND PASSIVE SONAR....................................................................................................4

CHAPTER 2-HISTORY OF SONAR..................................................................................................................5

CHAPTER 3-SONAR AND WARFARE.............................................................................................................7

CHAPTER 4-CIVILIAN USE OF SONAR...........................................................................................................9

CHAPTER 5-SCIENTIFIC USES OF SONAR....................................................................................................10

CHAPTER 6-ENVIRONMENTAL IMPACT OF SONAR....................................................................................12

CHAPTER 7-FUTURE OF SONAR.................................................................................................................14

REFERENCES..............................................................................................................................................16

TABLE OF FIGURES.....................................................................................................................................17

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INTRODUCTION OF SONAR

The following manuscript outlines the science, social, and natural uses and effects of Sonar

through history to present day. Sonar is a system that uses transmitted and reflected underwater sound

waves to detect and locate submerged objects or measure the distances underwater (see figure 1). It

has been used for submarine and mine detection, depth detection, commercial fishing, diving safety and

communication at sea. The sonar device will send out a subsurface sound wave and then listens for

returning echoes, the sound data is relayed to the human operators by a loudspeaker or by being

displayed on a monitor. The word sonar is an American term first used in World War II, it is an acronym

for SOund, NAvigation and Ranging. Nature has its own version of Sonar known as Echolocation, which is

used by animals such as dolphins, porpoises, bats, and whales. The use of sonar through military and

social means has created a positive impact for science and medicine, but also has a negative impact in

nature as well. The use of sonar in oceans can damage the animals in them, and even drive them away

from their residing areas.

Depending on the information desired, Sonar equipment can process responses from either

“passive” or “active” sound waves. Therefore Sonar is divided into active Sonar or Passive Sonar. Both

are used in submarines for military operations. Today’s electronic sonar processing can differentiate

between echoes about 12 millionths of a second apart. Bats have it down to 2 to 3 millionths of a

second. However bats can tell the difference between objects and shapes that are separated by only

about the width of a human hair. Unfortunately technology currently doesn’t allow us to see even 2 fish

swimming side by side apart.

As sonar has developed so have new instruments containing its fundamental uses. From the

scientific field to medical as well, sonar continues to influence innovation for future technology. Many

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research programs continue to discover the new ways in which sonar can and may eventually play a role

in our everyday lives.

Figure 1 SONAR OCEAN FLOOR MAPPING

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CHAPTER 1-ACTIVE AND PASSIVE SONAR

Active and Passive Sonar are the 2 general types of sonar that scientists use. Active sonar is a

system consisting of one or more transducers to send and receive sound. Transducers emit an acoustic

signal or pulse of sound into water. If an object is in the path of the sound pulse, the sound will bounce

off the object and echo to the sonar transducer. Depending on the transducer it has the ability to

receive signals and measure the strength of the signal. The transducer can also determine the range and

orientation of an object (Range = [ sound speed ] x [travel time ] / 2 )Active sonar processing involves

detection, classification, and localization. You first need to determine if an echo is present, the direction

of where the echo is coming from, and determine the position and velocity of the target that formed the

echo. This is a fundamental operation of active sonar.

Passive sonar is primarily used to detect noise from marine objects, such as submarines, ships,

and animals like whales. It is sonar that uses only under water listening equipment, with no transmission

of location revealing pulses (see figure 2). Unlike active sonar, passive sonar does not admit its own

signal which in some cases can be an advantage. It only detects sound waves coming towards it. Passive

sonar cannot measure the range of an object unless it is used in conjunction with other passive listening

devices. Both active and passive sonar are similar but serve different purposes.

Figure 2 PASSIVE SONAR

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CHAPTER 2-HISTORY OF SONAR

Daniel Colloden was the first person to grasp the concept of sonar. In 1822, he used an

underwater bell to calculate the speed of sound underwater in Switzerland. This underwater bell

worked as an ancillary for lighthouses to provide warnings of problems. From his research, many other

researchers and inventors were able to use his finding to create the sonar devices we have today.

After the Titanic sank in 1912, the idea of finding a way to detect icebergs was a prominent

focus for inventors and scientists. Through Daniel Colloden’s discovery of detecting sound under water,

Lewis Richardson, a meteorologist, used his discovery and turned it into action. He created the first echo

locator, which uses sound’s echo underwater for aerial navigation.

During WWI, the need to detect submarines underwater was crucial. The British made it a

primary focus to research sonar for finding the enemies ships. Paul Langévin worked with Russian

scientist Chilowski in inventing the first Sonar device for detecting Submarines in 1915, using quartz

piezoelectric crystals to produce the device. They called it “echo location to detect submarines”. In

1922-1923, sonar devices were being produced and manufactured for Naval vessels.

By WWII, information about sonar devices, in that time called ASDIC, was shared with the

United States. The US made many improvements to the former versions of ASDIC, and research on

underwater sound was expanded exponentially. They invented Sonobuoys, mine detecting sonar, and

dipping/dunking sonar. At the same time, many other countries were inventing counter-devices around

the world, using the same sonar technology. This involved Germany, where countermeasures were

made. Countermeasures were launched by a submarine being attacked to where the noise level is

dramatically raised, creating confusion for the attacker.

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During the 1930’s, The US developed a new underwater sound detection technology, which

coined the term we know now as Sonar (Sound Navigation and Ranging). The discovery of thermoclines

was made with this new technology. This is where a layer in a lake or large body of water, sharply

separates areas of different temperature, resulting in the temperature gradient across the layer is

abrupt.

Modern technology innovating has included side-scan sonar, rapid-scanning sonar, depth

detector, WPESS (within-pulse electronic sector scanning sonar). Modern technology for military uses

include systems used in acoustic mines, mine detection, and torpedoes (see figure 3). Atlas Elektronik is

a German company that has recently created new technology for mine detection. This is the first

unmanned operating system for mine detection, which is controlled by remote-control or autonomous.

Figure 3 SONAR FINDING UNDERWATER MINES

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CHAPTER 3-SONAR AND WARFARE

Since WWI, we have been advancing in Sonar technology. From the very first sonar detecting

device in 1912, we have been advancing greatly to have the sonar technology that we have today. This is

mainly beneficial in warfare, more particularly in Naval warfare. We are now able to find out the

position of submarines, how fast they are moving, detect torpedoes, and communicate with other

vessels.

In modern Naval warfare, active operation is mostly used. Active sonar detects the exact position of an

object. In active sonar, a signal is emitted and the sound wave travels from the emitting object. When

the sound wave hits an object, the wave reflects in many directions. The echo will allow the technician

to calculate from the sonar system he’s using, many different factors of the object in the water. For

example: the depth, water temperature, the frequency and the location of the reflecting object.

However, this can be dangerous at sea because the technician from a submarine will be able to detect

the emission of the sonar system detecting them. When hearing the signal of the enemys’ sonar, they

can use the energy of the sound wave to find the position of the ship, and the type of sonar using the

frequency detection. To reduce risk of being detected, the sonar is activated very quickly, at different

time intervals, to reduce detection from the enemy’s ship.

The invention of passive sonar has several advantages as well. It makes little to no noise, as opposed to

the very loud active sonar. It has greater range and allows the operating system to identify the target,

whereas active sonar, which has a shorter range and cannot identify the object. This is why passive

sonar is used as backup to active sonar.

The advance of sonar detecting the exact identification of the object has not yet been invented.

However we are becoming more advanced every year. We can still use sonar in very effective ways.

Another way we use passive sonar is used in a process called Target Motion Analysis or TMA. This

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detects the target’s range, course, and speed the object is going. It is used by marking the rate of the

frequency that is coming in at different times and comparing the motion of the enemy ship with the rate

of the ship doing the detecting. Although passive sonar is extremely useful, it is also the most costly.

Airplanes and helicopters also use sonar. Passive and active sonar are used in flying devices. In aircrafts,

active sonar is used to form sonobuoys, which are dropped in the area of possible enemy’s sonar (see

figure 4). Passive sonar is used by planes and helicopters to surprise enemy submarines. If a submarine

captain feels safe, he will bring the ship upward, close to the surface and be easier to detect because he

is not hiding under thermal layers, or deep and fast, making more sound. This is then helpful for

airplanes to detect the submarine and open fire.

Figure 4-SONOBOUY

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CHAPTER 4-CIVILIAN USE OF SONAR

Despite the fact that submarine warfare is governed by sonar, it isn’t only used by the military.

There is actually quite a few applications of it in civilian life, most of which involve bodies of water.

Just like in military use in submarines, sonar has found its home in the hands of fishermen. This

is one of the biggest civilian uses. One could imagine how difficult it would be to find fish in the vast

ocean. Throughout history there have been various methods used to do so. But for a growing world,

these methods don’t bring in as much as are in demand. Thus for a business that is based solely on the

capturing and selling of fish, this would make for a rough life. Because of sonar technology, fishing has

been able to be more productive.

In fishing, just like in other applications of sonar, it uses sound waves to “echo locate” the fish

(see figure 5). Since sound travels differently through water than it does through a fish (as they have

different densities), bodies of fish can be located. Since sound travels fast in water, it makes the

application of sonar very practical and has allowed for things such as competitive fishing to develop.

Figure 5 FISHERMAN USING SONAR

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CHAPTER 5-SCIENTIFIC USES OF SONAR

There are many uses of sonar in science and medicine. Several applications include biomass

estimation, wave measurements, water velocity measurements, bottom type assessment, bottom

topography measurement, sub-bottom profiling, synthetic aperture sonar, parametric sonar, fishy sonar,

echocardiology, ect.

Biomass estimation detects fish and other marine and aquatic life, and estimates their individual

sizes or total biomass using active sonar techniques. As the sound pulse travels through water it comes

across objects that are of different density or acoustic characteristics than the surrounding medium.

Bottom type assessment sonars have been developed that can be used to find the

characteristics of the sea bottom such as mud, sand, and gravel. Relatively simple sonars such as echo

sounders can be promoted to seafloor classification systems via add-on modules, converting echo

parameters into sediment type. Different algorithms exist and are based on the changes in the energy or

shape of the reflected sounder pings. Advanced substrate classification analysis can be achieved using

calibrated echo sounders and parametric or fuzzy-logic analysis of the acoustic data. Bottom topography

measurement is a side scan sonar that can be used to derive maps of the topography if an area by

moving the sonar across it just above the bottom. Synthetic aperture sonar is another application of

sonar that consists of various synthetic aperture sonars that have been built in the laboratory and used

in mine-hunting and search systems.

Echocardiology uses echocardiograms that use ultrasound transducers operating at very high

frequencies to obtain range resolutions of a few wavelengths (see figure 6). Echocardiograms show the

size, thickness and movement of the chambers, valves, and blood vessels in a beating heart.

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Figure 6 ECHOCADIOGRAM

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CHAPTER 6-ENVIRONMENTAL IMPACT OF SONAR

Although Sonar is very efficient in detecting underwater movement, mapping out locations,

warfare, and for underwater communication, it can also provide a negative effect on the environment.

Like many other aspects in technology, the negative impacts of the environment and organisms it comes

in contact with, are seen as less important in comparison with the boom it creates for society.

Marine animals such as whales and dolphins use echolocation systems for navigation and

survival. Echolocation systems in marine life are very much similar to technological forms of sonar. The

animal emits sound and interprets the vibrations in the water, using this to detect prey and mapping out

their location in water. Dolphins and whales use this for communicating with each other. They sense

prey by using clicks and emitting sound that then, bounces off prey, so they can locate their prey from a

wide range away where sight alone would not be effective. Whales and dolphins can interpret the

vibration coming back to them by time lapse that occurred in the echo from when they emitted the

sound to when it vibrates back, determining the distance of the object.

Whales, Dolphins, and bats use sonar the same way. They see through sound. They use this to

detect prey, avoid predators and large objects in the water, and communicate with each other. All the

aspects of their survival depend on their ability to use echolocation.

In the case of sonar, marine life is greatly affected. When humans use sonar devices around

marine animals and bats, the behavior of the animal rapidly change. Manmade waves of sound are so

powerful that they can be as loud as a rocket blast. During a live rocket blast, spectators typically have to

be 6-7 miles away, and even then, the noise is so loud, you can’t shout over it. Now imagine being ½ a

mile away from the noise blast without ear protection. The same thing happens with marine life, and

this is killing them by taking their biggest insuring factor of life away (see figure 7).

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Sonar emitted by human technology can emit sound waves that travel 300 miles away from the

source. These sonic waves can retain 140 decibels. This is 100 times more intense than the level that

changes behaviors in whales and dolphins. The noise emitted drowns out the sounds the animals rely on

for survival.

The animals are so effected by this sound, that they will avoid sonar by traveling outside their

natural breeding zone and thus decreasing their numbers. Whales and dolphins have a natural path that

they travel in their lifetime and if they are forced outside the direction of travel or their habitat, they can

get lost and stray themselves from their pod, resulting in death. Many times the sound waves cause

them to get lost, which at times gets them stranded too close to shore and die. The government’s

investigating established that mid-frequency sonar causes stranding of these animals. These stranded

whales have been shown to have bleeding around their ears and brain from the effects of these gigantic

sound waves.

The navy estimates that due to increasing sonar training, it will have significant harm on marine

mammals more than 10 million times during the next five years off the US coast alone.

The way we can coexist with marine animals the most effectively and without endangering the

wildlife, is by only using active sonar outside areas where these animals feed, migrate, and calf.

Figure 7 SONAR DAMAGE TO ANIMALS

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CHAPTER 7-FUTURE OF SONAR

There are many research projects that are looking to upgrade technology for the future using

sonar and its principles. Research using metamaterials that can bend sound waves around an object

gives the future option of a new invisibility cloak for sound which could help doctors find tiny tumors or

hide submarines from enemy sonar ( see figure 8-9).

Researchers at the Florida Institute for Human and Machine Cognition envision their work giving

Army Rangers 360-degree unobstructed vision at night and allowing Navy SEALs to sense sonar in their

heads while maintaining normal vision underwater. This idea would be accomplished by using a narrow

strip of red plastic connects the Brain Port to the tongue where 144 microelectrodes transmit

information through nerve fibers to the brain.

Another near future technology is using sonar to help the blind. At the Hebrew University in

Israel, a team has a new device that one day would be able to help the blind detect objects within 10

meters to help them navigate. The handheld device sends a focused beam in the direction chosen by the

user while other sensors detect the distance and the height of all surrounding objects. The information

is transmitted back to the user through vibrations, allowing users to create a picture of his surroundings

in their head. These vibrations are then turned into vibrations of light so a user can see.

Many other projects are currently being discussed by other engineers and Universities for

research that seems to just be expanding and waiting for exploration. In short, sonar has revolutionized

technology for the military and civilian use, and will continue to do so as these ideas and experiments

mature.

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Figure 8 METAMATERIAL BENDING WAVES

Figure 9 METAMATERIAL BENDING LIGHT

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REFERENCES

Chapter 1- wikipedia

Chapter 2- http://www.edinformatics.com/inventions_inventors/sonar.htm

http://inventors.about.com/od/sstartinventions/a/sonar_history.htm

http://www.solarnavigator.net/sonar.htm

Chapter 3-http://www.solarnavigator.net/sonar.htm/ http://www.marinelink.com/article/sonar

Chapter 4- maqsonar.com/ sonarfishing.com/

Chapter 5 – Wikipedia/ Mark Denny, Blip, Ping, and Buzz… Making sense of Radar and Sonar/

John Hopkins University

Chapter 6 - http://www.nrdc.org/wildlife/marine/protectingwhales.asp

http://www.nrdc.org/wildlife/marine/sound/contents.asp

http://www.nrdc.org/wildlife/marine/sonar.asp

http://www.associatedcontent.com/article/1049119/marine_animals_and_sonar_pg3.html?cat=58

Chapter 7-http://nextbigfuture.com/2009/06/sound-technology-roundup-sonar-cloaking.html

http://www.socnet.com/showthread.php?t=59218

http://fullytechnoid.com/?p=145

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TABLE OF FIGURES

Figure 1 SONAR OCEAN FLOOR MAPPING- http://www.history.navy.mil/pics/elem2.gif...........................3

Figure 2 PASSIVE SONAR- http://img.nauticexpo.com/images_ne/photo-g/boat-forward-looking-sonar-

229449.jpg......................................................................................................................................... 4

Figure 3 SONAR FINDING UNDERWATER MINES-

http://www.atmarine.fi/ckfinder/userfiles/images/SA9500.JPG................................................................6

Figure 4-SONOBOUY- http://www.phoenixsandt.com/images/navairmeas.jpg.........................................8

Figure 5FISHERMAN USING SONAR- http://www.tritonmike.com/xplosion6.JPG......................................9

Figure 6 ECHOCADIOGRAM- http://www.hypertensionblog.org/wp-content/uploads/2007/08/ecg.jpg.11

Figure 7 SONAR DAMAGE TO ANIMALS-

http://conservationreport.files.wordpress.com/2008/10/beaked-whale.jpg...........................................13

Figure 8 METAMATERIAL BENDING WAVES-

http://www.techpin.com/wp-content/uploads/2008/12/metamaterial_design-s.jpg.............................15

Figure 9 METAMATERIAL BENDING LIGHT-

http://metallurgyfordummies.com/wp-content/uploads/2011/07/metamaterials.jpg

http://metallurgyfordummies.com/wp-content/uploads/2011/07/metamaterials.jpg............................15