1. Using Sound for many purposes
Sound waves have many purposes for both humans and animals
Understanding intensity, pitch and the Doppler Effect has enabled scientists to develop complex forms of technology, such as ultrasounds, fish-finders, and music-editing machines
In this section, you will be learning about the following processes:
Acoustics : which is used for designing concert halls and sound-proof rooms
Echolocation: which is how bats and dolphins communicate, or locate prey and predators
Sonar: which is used to map the ocean floor or locate schools of fish
Sonograms: which are pictures created of the insides of bodies
What do most of these processes have in common?
Most of these processes involve the use of echoes and the use of ultrasonic waves (waves above the human hearing frequency; above 20,000 Hz)

2. Echolocation- is the use of reflected sound waves to determine distances or to locate objects
Dolphins and bats rely on ultrasonic waves (those above 20,000 Hz) to locate prey or communicate with other members of their species
Here’s how it works for dolphins:
1. the dolphin sends out the ultrasonic waves
2. ultrasonic waves reflect off the prey
3. the dolphin uses the reflected waves to detect obstacles or prey
If the sound reflects back quickly, then prey is nearby
They also rely on the Doppler Effect:
If the pitch is higher, the prey are coming toward the dolphin
If the pitch is lower, then the prey are moving away from the dolphin

3. 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.

4. Sonar works a lot like echolocation, except that this method is used by machines
Sonar is a system that uses reflected sound waves to detect and locate objects underwater
The word S.O.N.A.R. comes from the initial letters of sound navigation and ranging
Navigation means finding your way around the ocean (or air) and ranging means finding the distance between objects
Today, sonar is used to determine the depth of water, to map the ocean floor, and to locate sunken ships, schools of fish, and other objects in the ocean
Sonar

5. How Sonar Works:
A sonar device sends a burst of ultrasonic waves that travel through water
When the sound waves strike an object or the ocean floor, they reflect, and a hydrophone detects theses reflected waves
The farther away a sound travels before bouncing off an object, the longer it takes to return to the sonar device

6. Ultrasounds/ Sonograms
Doctors use ultrasound imaging to look inside the human body
Ultrasound devices send ultrasonic waves into the body and detect reflected sound waves
Different parts of the body, such as bones, muscles, the liver or the heart, reflect sounds differently because of their densities
The device that uses the reflected ultrasonic waves to create a picture is called a sonogram
A doctor holds a small probe over a pregnant woman’s abdomen and the probe sends out a 4 million Hz wave, and the device uses the reflected sound waves to produce a sonogram
Doctors can use sonograms to diagnose patients, or find out positioning of a developing baby
They can also detect if more than one baby will be born

7. Acoustics You may think of our auditorium when you think of acoustics
Acoustics is the study of how sounds interact with each other and the environment
Sound waves can interfere with each other in 2 ways:
Constructive interference- can distort sounds
Destructive interference - can produce dead spots, where loudness is reduced
You can also hear echoes as sound waves reflect back and forth off hard surfaces
This is reverberation, in which the echoes of a sound are heard after the sound source stops producing waves
The sound of a handclap can take more than a second to die out in a gym
This is why acoustics is used in the design of concert halls to control interference and reverberation

8. Different surfaces change the amount of reverberation
Curved, hard surfaces are used to direct sound waves to different parts of the concert hall
Curved walls
Wooden panels
High ceilings
Soft surfaces absorb sound waves, reducing reverberation
Cloth or velvet curtains
Carpeted floors and walls
Seat cushions
But some reverberation is good, otherwise instruments would sound thin and distant
With too much reverberation, reflected waves interfere and individual notes become hard to pick out