Transcript Sound - Images

Sound
Sound
• Sound
– form of energy
– all sounds are made by
vibrations
– sound moves through
mediums as a
compressional wave
How Does Sound Travel?
1. Objects vibrate
2. Vibrations transfers
energy
3. Causes collisions of
nearby air molecules
4. These molecules then
collide with others
5. These collisions and
energy transfers form
the sound wave
Speed of Sound
• Most sound waves
travel through air
• BUT sound can travel
through solids, liquids
or gases
• Sound travels faster in
solids and liquids than
gases
Speed of Sound
Medium
sound speed (m/s)
air (20C)
343
water
1497
gold
3240
brick
3650
wood
3800–4600
glass
5100
steel
5790
aluminum
6420
Breaking the Sound Barrier
• Chuck Yeager broke
sound barrier in 1947
• Speed of sound at 68° F
(20° C) is 768 mph
• Breaking the sound
barrier
Anatomy of the Ear
Properties of Sound
• Intensity
– Amount of energy that
flows through an area in
a certain amount of time
– Lower volume, lower
intensity
– Less intensity, less
distance the sound wave
will travel
Properties of Sound
• Loudness
– Human perception of
sound intensity
– Measured in Decibels
– 0 dB (faintest sound)
– >120 dB (pain threshold)
Cilia of the Cochlea
• Normal
• Moderate Sound Damage
• Serious Damage
Process of Hearing
• Process of Hearing
Properties of Sound
• Pitch
– Highness or lowness of a
sound
– Higher the pitch, higher
the frequency
– Lower the pitch, lower
the frequency
– Pitch expressed as
musical notes (C, F
sharp, E flat etc. .)
Frequency Range
• Human voice range from
250 to 4000 Hz range
• Human ear can hear
frequencies between 20 Hz
and 20,000 Hz
• Frequency Hearing Test
• Frequency Ranges:
Properties of Sound
• Ultrasonic
– Sound frequencies
above 20,000 Hz
• Infrasonic/Subsonic
– Sound frequencies
below 20 Hz
– Elephant's Subsonic
Sounds
Properties of Sound
• Doppler Effect
– Change in pitch or wave
frequency due to
movement
– The Doppler Effect can
occur when the source
of a sound is moving or
the listener is moving in
relation to the source of
the sound
Music
• Music
– Sounds that are
deliberately used in a
regular pattern
– Natural frequencies
• All objects have a natural
frequency at which they
vibrate
– Resonance
• Amplifies the sound of
musical instruments
Pythagoras and Music
Sound Quality
• Sound Quality
– Describes differences
among sounds of the
same pitch and loudness
• Overtone
– Other frequencies
besides the fundamental
that exist in musical
instruments
– Different instruments =
different overtones
Overtones
• All are playing the same
note
• Have the same
wavelength and
frequencies
• Because of overtones,
very different sound
Musical Instruments
• Strings
–
–
–
–
Violins
Guitars
Harps
Cello
– Usually have resonators
• Resonator
– Hollow chamber filled with
air that amplifies sound
Musical Instruments
• Brass and Woodwinds
–
–
–
–
Horns
Trumpets
Flutes
Oboes
– Brass uses cone-shaped
mouthpieces to cause air
to vibrate
– Woodwinds use wooden
reeds to cause air to
vibrate
Musical Instruments
• Percussion
– Drums
– Xylophone
– Drums use membrane
stretched across a
resonator
– Xylophones use tubeshaped resonator
Using Sound
• Acoustics
– Study of sound
• Echolocation
– Process of locating
objects by emitting
sounds and interpreting
the sound waves
reflected back
Using Sound
• Sonar
– System that uses the
reflection of underwater
sound waves to locate
objects
Using Sound
• High frequency sound
waves used in many ways:
– Remove dirt and buildup
from jewelry
– Detects and monitors many
medical conditions
• Pregnancy
• Heart Disease
– Break up kidney stones
– Produces images of
internal body structures