1. Sound
The Nature of Sound

2. Sound waves
Interactions
of sound
Reflection
travels through a medium
longitudinal wave
begins with a vibration-back and forth motion
reflected sound called an echo
hard, smooth surface = stronger reflection

3. Reflection
Sound Waves

4. Refraction Diffraction Interference Speed of Sound
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
Speed of Sound

5. Mediums and Sound Elasticity
Density
Temperature
more elastic a medium faster sound travels
travels fastest in solids
does not travel well in liquids and gases
sound travels slower in dense materials
sound travels slower at lower temperatures and higher altitudes

6. Properties of Sound describes your perception of the energy of a sound
Loudness
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

7. Energy of a sound source
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

8. Intensity
Measuring
Loudness
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

10. Pitch
Pitch &
Frequency
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

11. 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

13. 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
Shock Waves
Sound Quality

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

15. How you Hear Sound Human Ear Outer Ear
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

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

18. 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

19. Using Sound

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