Using Sound for many purposesUsing Sound for many purposes Sound waves have many purposes for both Sound waves have many purposes for both humanshumans and and

animalsanimals Understanding intensity, pitch and the Doppler EffectUnderstanding intensity, pitch and the Doppler Effect has has

enabled scientists to develop complex forms of technology, enabled scientists to develop complex forms of technology, such as ultrasounds, fish-finders, and music-editing such as ultrasounds, fish-finders, and music-editing machines machines

In this section, you will be learning about the following In this section, you will be learning about the following processes:processes:– Acoustics :Acoustics : which is used for designing concert halls and which is used for designing concert halls and

sound-proof rooms sound-proof rooms – Echolocation:Echolocation: which is how bats and dolphins which is how bats and dolphins

communicate, or locate prey and predatorscommunicate, or locate prey and predators– Sonar:Sonar: which is used to map the ocean floor or locate which is used to map the ocean floor or locate

schools of fishschools of fish– Sonograms:Sonograms: which are pictures created of the insides of which are pictures created of the insides of

bodiesbodies What do most of these processes have What do most of these processes have in commonin common??

– Most of these processes involve the Most of these processes involve the use of echoesuse of echoes and and the the use ofuse of ultrasonic wavesultrasonic waves (waves above the human (waves above the human hearing frequency; above 20,000 Hz)hearing frequency; above 20,000 Hz)

EcholocationEcholocation- is the use of reflected sound waves - is the use of reflected sound waves to determine distances or to locate objectsto determine distances or to locate objects

Dolphins and bats rely on Dolphins and bats rely on ultrasonic wavesultrasonic waves (those above (those above 20,000 Hz20,000 Hz) to ) to locate preylocate prey or or communicatecommunicate with other members of their with other members of their speciesspecies

Here’s how it works for dolphins:Here’s how it works for dolphins:– 1. the dolphin sends out the ultrasonic 1. the dolphin sends out the ultrasonic

waveswaves– 2. ultrasonic waves reflect off the prey 2. ultrasonic waves reflect off the prey – 3. the dolphin uses the reflected 3. the dolphin uses the reflected

waves to detect obstacles or preywaves to detect obstacles or prey If the sound reflects back quickly, then prey is If the sound reflects back quickly, then prey is

nearbynearby They also rely on the They also rely on the Doppler EffectDoppler Effect::

– If the pitch is If the pitch is higherhigher, the prey are , the prey are coming coming towardtoward the dolphin the dolphin

– If the pitch is If the pitch is lowerlower, then the prey are , then the prey are moving awaymoving away from the dolphin from the dolphin

Echolocation by Dolphins:A dolphin sends out an ultrasonic wave and detects the reflected wave.

1. The dolphin sends out ultrasonic waves

2. Ultrasonic waves reflect off the fish.

3. The dolphin uses the reflected waves to detect obstacles or prey.

SonarSonar SonarSonar works a lot like works a lot like

echolocation, except that this echolocation, except that this method is used by method is used by machinesmachines

SonarSonar is a system that uses is a system that uses reflected sound waves to detect reflected sound waves to detect and locate objects underwaterand locate objects underwater

The word The word S.O.N.A.RS.O.N.A.R. . comes comes from the initial letters of from the initial letters of sosound und nnavigation avigation aand nd rranginganging

NavigationNavigation means finding your means finding your way around the way around the ocean (or air)ocean (or air) and and rangingranging means finding the means finding the distance between objectsdistance between objects

Today, sonar is used to Today, sonar is used to determine the determine the depthdepth of water, of water, to to mapmap the ocean floor, and to the ocean floor, and to locate locate sunken ships, schools of sunken ships, schools of fish, and other objectsfish, and other objects in the in the oceanocean

How Sonar Works:How Sonar Works: A sonar device sends a A sonar device sends a

burst of burst of ultrasonic ultrasonic waveswaves that travel that travel through waterthrough water

When the sound waves When the sound waves strike an object or the strike an object or the ocean floor, they ocean floor, they reflectreflect, and a , and a hydrophonehydrophone detects detects theses reflected wavestheses reflected waves

The The farther awayfarther away a a sound travels before sound travels before bouncing off an object, bouncing off an object, the the longerlonger it takes to it takes to return to the sonar return to the sonar devicedevice

Ultrasounds/ SonogramsUltrasounds/ Sonograms Doctors use ultrasound imaging to look inside the Doctors use ultrasound imaging to look inside the

human bodyhuman body Ultrasound devicesUltrasound devices send send ultrasonic wavesultrasonic waves into into

the body and detectthe body and detect reflected reflected sound waves sound waves Different partsDifferent parts of the body, such as bones, of the body, such as bones,

muscles, the liver or the heart, muscles, the liver or the heart, reflectreflect soundssounds differently because of their differently because of their densitiesdensities

The device that uses the reflected ultrasonic The device that uses the reflected ultrasonic waves to create a waves to create a picture picture is called a is called a sonogramsonogram

A doctor holds a small probe over a pregnant A doctor holds a small probe over a pregnant woman’s abdomen and the probe sends out a woman’s abdomen and the probe sends out a 4 4 million Hz wavemillion Hz wave, and the device uses the , and the device uses the reflected sound waves to produce a reflected sound waves to produce a sonogramsonogram

Doctors can use sonograms to Doctors can use sonograms to diagnose diagnose patientspatients, or , or find out find out positioningpositioning of a developing of a developing babybaby

They can also detect if They can also detect if more than onemore than one baby will baby will be bornbe born

AcousticsAcoustics You may think of our auditorium when you think of acousticsYou may think of our auditorium when you think of acoustics AcousticsAcoustics is the study of how sounds is the study of how sounds interactinteract with each with each

other and the environmentother and the environment Sound waves can interfere with each other in 2 ways:Sound waves can interfere with each other in 2 ways:

– Constructive interference-Constructive interference- can distort sounds can distort sounds– Destructive interferenceDestructive interference - - can produce dead spots, can produce dead spots,

where loudness is reducedwhere loudness is reduced You can also hear You can also hear echoes echoes as sound waves reflect back and as sound waves reflect back and

forth off hard surfacesforth off hard surfaces This is This is reverberationreverberation, in which the , in which the echoesechoes of a sound are of a sound are

heard afterheard after the sound source stops producing waves the sound source stops producing waves The sound of a handclap can take more than a second to die The sound of a handclap can take more than a second to die

out in a gymout in a gym This is why acoustics is used in the design of This is why acoustics is used in the design of concert hallsconcert halls to to

control control interferenceinterference and and reverberationreverberation

Different surfaces change the Different surfaces change the amount of reverberationamount of reverberation

CurvedCurved, hard surfaces are used to , hard surfaces are used to direct sounddirect sound waves to different parts of the concert hall waves to different parts of the concert hall – Curved wallsCurved walls– Wooden panelsWooden panels– High ceilingsHigh ceilings

SoftSoft surfaces surfaces absorbabsorb sound waves sound waves, reducing , reducing reverberation reverberation – Cloth or velvet curtainsCloth or velvet curtains– Carpeted floors and wallsCarpeted floors and walls– Seat cushionsSeat cushions

But some reverberation But some reverberation is is goodgood, otherwise instruments , otherwise instruments would would sound thinsound thin and and distantdistant

With too much reverberation, reflected waves interfere With too much reverberation, reflected waves interfere and and individual notes become individual notes become hard to pick outhard to pick out