Download Part 1: Sound Waves - Science with Mr. Enns

Sound
Part 1: Sound Waves
Recall
There are two major categories of waves.
Mechanical
Waves that transfer energy
through matter.
Electromagnetic
Waves that transfer energy
through a field.
They require a substance (a
medium) to travel through.
They do NOT require a
substance (a medium) to
travel through.
e.g. water, sound,
seismic waves
e.g. light, radio,
ultraviolet, x-rays
What Are Sound Waves
Sound waves are created when an object vibrates.
When an object vibrates, it
creates longitudinal waves.
Properties of Sound Waves
Sound waves have 3 main properties.
1. Speed
How fast the sound wave moves in a medium.
2. Loudness
How intense the sound is.
3. Pitch
The frequency of the sound wave.
1. Speed
The speed of sound depends on the medium.
Sound waves travel faster
through more dense mediums.
more dense
Gases
Liquids
Solids
769 mph
1400 mph
5000 mph
1. Speed
Table: Speed of sound for different materials
less dense
more dense
Dry Air
331 mph
Fresh Water
1509 mph
Salt Water
1546 mph
Lead
1210 mph
Iron
4480 mph
Aluminum
5170 mph
2. Loudness
Loudness is how intense the sound is.
The intensity of a sound is a measure of
how much energy the sound wave has.
The amplitude (height)
of a sound wave shows
its loudness.
2. Loudness
lower amplitude
higher amplitude
less energy
more energy
SOFTER
LOUDER!
2. Loudness
Loudness is measured in decibels (dB).
The decibel scale measures sound intensity.
A 0 db sound can barely be heard.
A 100 db sound can cause hearing loss.
Interactive Loudness Scale
2. Loudness of Different Sounds
Threshold of hearing
0 db
Whisper
15 - 20
Normal conversation
40 - 50
Street noise
60 - 70
Rock concert
110 - 120
Threshold of pain
120
Jet take off
120 - 160
3. Pitch
Pitch is how high or how low a sound is.
The frequency of a sound wave
determines the pitch of the sound.
The wavelength of
a sound wave
shows its frequency.
3. Pitch
1 sec.
1 sec.
lower frequency
higher frequency
lower pitch
higher pitch
e.g. tuba
e.g. flute
Music vs. Noise
Music and noise are different.
It depends on the shape of the sound wave.
Noise
Music
No clear pattern
A clear pattern
Timbre
No two types of instrument sound the
same, even when playing the same note!
This is because each instrument makes
its own unique pattern of sound waves.
The particular sound that
an instrument or human
voice has it called its
timbre (TAM-buhr).
Timbre
No two types of instrument sound the
same, even when playing the same note!
This is because each instrument makes
its own unique pattern of sound waves.
Review!
A
B
C
D
Which of the sound waves has the...
Highest volume?
Lowest volume?
Highest pitch?
Lowest pitch?
Any Questions?
Sound
Part 2: The Ear
Introduction
Ears are sense organs that respond to sound.
Your ear converts sound waves into electrical
signals that your brain interprets.
The ear’s structure is
designed to receive
and transmit the
sound waves…
Parts of the Ear
The ear is divided
into 3Ear
major sections:
The Outer
Contains the pinna, ear canal and ear drum
The Middle Ear
Contains three bones: hammer, anvil & stirrup
The Inner Ear
Contains the cochlea and auditory nerve
Parts of the Ear
Outer Ear
Middle Ear
Inner Ear
anvil
pinna
hammer
stirrup
ear canal
cochlea
ear drum
auditory nerve
The Outer Ear
The Outer Ear
The Outer Ear
The pinna is specially shaped to gather and
focus sound waves and direct them into the ear
The ear canal is a hollow tube that carries
the sound waves to the ear drum
The sound waves hit the ear drum, causing it to
` vibrate. The ear drum transmits
these vibrations
into the inner ear where they are amplified
The Ear Drum
The Middle Ear
The Middle Ear
The Middle Ear
Has the smallest bones in the human body:
the hammer, anvil and stirrup
Their job is to amplify the vibrations of the ear
drum and transmit it into the inner ear
The stirrup “taps” on the inner ear at a
` spot called the
oval window
Stirrup
Inner Ear Bones
Ham
me
r
Inner Ear Bones
The Inner Ear
The Inner Ear
The Inner Ear
The cochlea is a snail-shaped tube that is lined
with receptors that respond to sound
The receptors are tiny hair cells that shake
back and forth in response to sound waves
When they shake, the hair cells create
` electrical signals called nerve
impulses which go
to the brain along the auditory nerve
The Cochlea
Hair Cells
Analogy for Inside the Cochlea
A seagrass meadow
High vs. Low Sounds
High pitch sounds carry more energy and
travel further into the cochlea
Lower pitch sounds carry less energy and
don’t travel as far into the cochlea
A Final Look!
Outer Ear
Middle Ear
Inner Ear
The Main Idea
§  The ear is divided into 3 sections: the
outer ear, middle ear and inner ear.
§  At the outer ear, sound waves are focused by
the pinna down the ear canal to the eardrum.
§  The sound waves make the eardrum vibrate.
§  The vibrations are amplified by the 3 middle
ear bones: the hammer, anvil and stirrup.
§  The stirrup transfers the vibrations to the
cochlea within the inner ear.
§  The vibrations activate hair cells inside the
cochlea, which send electrical signals to the
brain along the auditory nerve.
§  The brain interprets these signals as sound.
Any Questions?