1. The Nature of Sound Chapter 21

2. Objectives: THINK: Why is sound important?
Physical Standard 1
I will be able to describe sound wave characteristics that are common among other forms of waves.
I will be to differentiate unique characteristics of sound.
THINK: Why is sound important?

3. Close Your Eyes and Listen:
Click
Click
Click
Click
Click
Click

4. Sound waves
Interactions
of sound
Reflection
travels through a medium (solid, liquids or gases)
longitudinal wave
Sound travels by sending vibrations -back and forth motion - through matter
Pair and Share: Why can’t you hear sound in outer space? How do they communicate with each other?
reflected sound called an echo
hard, smooth surface = stronger reflection

5. Reflection
Sound Waves

6. REVIEW WAVE: Refraction Diffraction Interference
Bending of sound waves as it passes from one medium to another
Bending of waves around a barrier
sound waves meet
constructive increases sound
destructive decreases sound
at room temp, sound travels at 343 m/s
speed depends on medium it travels though
Refraction
Diffraction
Interference
Illustrate the three above
Speed of Sound

7. Mediums and Sound Elasticity Density Temperature
more elastic a medium faster sound travels
Solid: fastest speed
Liquid: medium speed
Gas: slow speed
Vacuum: no sound
sound travels slower in dense materials
sound travels slower at lower temperatures and higher altitudes
Pair and Share: Why does this happen?
Elasticity
Density
Temperature

8. Properties of Sound describes your perception of the energy of a sound
describes what you hear
depends on 2 factors:
energy of sound source
distance from sound source
The Coolest Things Sound Wave Can Do
Find someone and share video
Loudness
A medium is a material that sound, a form of energy, need to transfer
Speed of sound
Solid : Fast speed
Liquid : Medium speed
Gas : Slow Speed
Standard Temperature and Pressure = 3.31 x 102 m/s
Vacuum : No Sound

9. Energy of a sound source
Think: Draw an example
Distance from a sound source
greater energy used  louder sound
more energy  greater amplitude (vibration)
large amplitude loud sound
loudness increases the closer you are to a sound source

10. amount of energy a sound wave carries per second through a unit area
greater intensity sounds louder
unit decibel (dB)
sound barely heard = 0 dB
sound louder than 100 dB can damage ears
Intensity
Measuring
Loudness

12. Pitch
Pitch &
Frequency
Pitch and Frequency Video
description of how high or low the sound seems to a person
depends on frequency of the wave
high frequency  higher pitch
low frequency  low pitch
can hear sounds with frequency between 20 Hz and 20,000 Hz

13. Ultrasound
Infrasound
Doppler Effect
sound waves with frequency above normal human range
frequency below human range of hearing
change in frequency of a wave as its source moves in relation to an observer
change in frequency is heard as a change in pitch

15. Shock Waves
Sound Quality
shock waves form as sound waves overlap
release huge amounts of energy
sonic boom heard when they pass by
Blending of several pitches through interference

16. Noise
Music
Random mix of frequencies that are
not pleasing
set of frequencies that combine in patterns that are pleasing

17. How you Hear Sound function: gather sound waves and send info to brain
three main sections: outer, middle, inner
collects sound waves and directs them to ear canal which vibrates eardrum
Human Ear
Outer Ear

18. Middle Ear
Inner Ear
contains 3 small bones that increase size of vibrations
Vibrations are changed into electrical signals for the brain to interpret

20. can occur if eardrum is damaged
loud sounds can damage hair cells in inner ear won’t get messages to brain
old age hair cells gradually die harder to hear
amplify sound
Hearing Loss
Hearing Aids

21. -use of reflected sound waves to determine distances or locate objects
-animals use this to navigate and find food  Bats, dolphins
Echolocation