The Nature of Sound - Travellin...The Nature of Sound Author sarah.irwin Created Date 7/22/2011 6:19:11 AM ...

The Nature of Sound

Section 3:

Interactions of Sound Waves

Essential Questions

How are echos made?

How can an echo help locate an object?

What is constructive interference?

What is destructive interference?

What is resonance?

Vocabulary

Echo – the bouncing back of a sound wave after striking a barrier

Echolocation – using reflected sound waves to find objects

Interference – combination of two or more waves into one wave• Can be constructive or destructive

Sonic boom – loud boom caused by an object traveling faster than the speed of sound

Vocabulary, continued

Standing wave – pattern of vibrations that look like a wave that is standing still

Resonance – when a vibrating object causes a second object to vibrate

Reflection of Sound Waves

Reflection – sound waves bouncing back after striking an object

• Also known as an echo

Echolocation – using echoes to find an object

• Used by some animals: dolphins, bats, some whales, some birds

Reflection of Sound Waves 2

Sonar (sound navigation and ranging) –electronic echolocation

• Sonar uses ultrasonic waves to find objects or create maps

Ultrasonography – using echoes to “see” inside a patient’s body

• Safer than x-rays

• Ex: commonly used to “look at” developing fetuses

Interference of Sound Waves

Interference – when two or more sound waves overlap

• Constructive interference – when waves overlap, the amplitude is increased so the sound becomes louder (Think: constructive = build)

• Destructive interference – waves begin to cancel each other out, decreasing the amplitude so the sound becomes softer (think: destructive = tear down)

Interference of Sound Waves 2 Supersonic speeds – faster than the

speed of sound

• The constructive interference creates a shock wave

Sonic boom – sound heard when a shock wave has occurred

• Can damage hearing and objects

Interference of Sound Waves 3

Standing wave – a wave that looks like it is standing still

• Maximum amplitude = constructive interference

• Seems to be still = destructive interference

Fundamental frequency – the one standing wave that you can see

Resonant frequency – frequency where standing waves can be seen

Resonance

Resonance – when a vibrating object causes a second object to vibrate

Used in musical instruments