Sound
Overview
•The Facts of Sound
•Sound Vocabulary
•The Ear and Sound
•Musical Instruments and
other uses of Sound
•Other types of waves
The Facts
Sound …
1. … is a form of energy produced &
transmitted by vibrating matter
2. … travels in longitudinal waves
3. …travels faster through solids than
liquids or gases
Sound waves and
Sound waves travel faster through solids because
there are more particles close together to transfer
the energy.
Speed of Sound
•
Medium (Matter)
o
gas
air (0 C)
o
liquid
solid
air (20 C)
o
water (25 C)
sea water
iron
copper
glass
diamond
Speed m/sec
331
343
1493
1533
5130
3560
5640
12000
Vibration
- Very fast, repeated backward and forward
movement of particles of matter
-
For example, the vibration of the tuning fork creates pure sound.
-
The hammer hits the nail and the particles vibrate making noise.
Waves transport energy without
moving matter
Watch the 3
red dots
You will see
them vibrate,
but not move
with the wave
to the end.
All the
particles are
vibrating but
stay fixed
Sound Waves
- Alternating areas of high and low pressure
in the air (compressions and rarefactions)
Sound Waves
- ALL sound is carried through matter
as sound waves. In a vacuum there are no
particles so sound cannot travel.
-
Alternating areas of high and low pressure in the air (compressions
and rarefactions)
Sound Waves
- Sound waves need particles to be
transmitted they are mechanical waves
-
ALL sound is carried through matter as sound waves. In a vacuum
there are no particles so sound cannot travel.
-
Alternating areas of high and low pressure in the air (compressions
and rarefactions)
Sound Waves
- Sound waves move out in ALL
directions from a vibrating object.
-
Sound waves need particles to be transmitted they are mechanical
waves
-
ALL sound is carried through matter as sound waves. In a vacuum
there are no particles so sound cannot travel.
-
Alternating areas of high and low pressure in the air (compressions
and rarefactions)
Compression
Where particles are pressed
together as the sound wave moves
through matter.
• Compressions - The close together parts of the wave.
• Rarefactions - The spread-out parts of a wave.
Compression Wave = Longitudinal Wave
Longitudinal Wave
(Compression Wave)
Each wave particle vibrates back
and forth in the same direction of
the wave.
Sound waves covered till now:
• States of matter (solid, liquid, gas)
• Speed of sound through matter
• No sound in a vacuum
• Vibration
• Compression + Rarefaction
• Longitudinal waves
•Remember that ….waves transfer
energy without moving matter
Wavelength & Frequency
- Wavelength is the distance between one
part of a wave and the same part of the
next wave
- Frequency is the number of waves passing
a point in a certain time
-
Many waves = high frequency
Few waves = low frequency
Pitch = Frequency
• How high or low a sound is
• Pitch depends on the frequency of a sound wave
• For example,
- Low pitch
- High pitch
- Low frequency
- High frequency
- Longer wavelength
- Shorter wavelength
Frequency is measured in Hertz
• For example:
If 20 waves are made per
second, then the frequency
is 20 cycles per second =
20 Hertz
•Hz
The human ear can only hear
sounds between
20Hz and 20,000 Hz (Frequency/Pitch)
20 Hz – 20,000 Hz
Below 20 Hz is called infrasound
Above 20,000 Hz is called ultrasound
The Ear
• Sounds reach our ears through vibrating
air particles
• Our ears capture sound waves and turn
them into signals that go to our brains
• Sound waves move through 3 parts of the
ear; outer ear, middle ear, + inner ear
Amplitude
is the maximum distance
the particles in a wave
vibrate from their rest positions.
Amplitude = loudness
• The intensity of a
sound decreases as
you move away from
a sound. The sound
gets softer.
• As the source of a
sound comes closer
the sound becomes
louder, more intense
soft
loud
• A loud sound has a
high amplitude
• A soft sound has low
amplitude
Amplitude = loudness
•The volume or loudness of
sound is measured in
decibels
dB
Loudness of Sound in Decibels
Sound
Loudness (db)
Hearing
damage
Average Home
40-50
Loud Music
90-100
After long
exposure
Rock Concert
115-120
Progressive
Jet Engine
120-170
Pain
Sound and Instruments
- Different musical instruments create
different sound vibrations
- Wind instruments by blowing and
vibrating the air e.g. flute, saxophone, organ
- String instruments by touching and
vibrating the strings
e.g. guitar, violin, piano
- Percussion instruments by hitting a
surface e.g. drums, cymbals, triangle
Sound and Instruments
- Instruments can be played at different pitches
(musical notes) by changing the lengths of
different parts.
- For example,
- Another way to make different pitches is to
change the thickness of the material that
vibrates.
A trombone’s mute absorbs
some of the sound waves
produced, so a different
sound is made.
Sonar
- Sonar uses reflected sound waves (echoes)
to find objects in water or air
Humans use sonar
to locate or find
objects
Animals use sonar or echo location to find their
prey (food); these sounds have such a high pitch
or frequency that the human ear cannot hear
them
Ultrasound (above 20,000 Hz)
Ultrasound waves are used in medicine
They are also reflected sound waves
Other types of waves
• Remember sound waves are longitudinal
and mechanical
•Other waves are transverse,
electromagnetic and water
waves
Transverse waves
wave particles vibrate
in an up-and-down motion.
Transverse waves
• Crests - Highest part of a wave
• Troughs - The low points of the wave
Electromagnetic waves
• Electromagnetic waves travel as
transverse waves
• Electromagnetic waves CAN travel
through a vacuum
• Light, microwaves, x-rays, and TV and
radio transmissions are all examples of
electromagnetic waves
Water Waves
• The blue surface particles move in a clockwise direction
Wave concepts covered in this power point:
Sound Waves
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
States of matter (solid, liquid, gas)
Speed of sound through matter
No sound in a vacuum
Vibration
Compression + Rarefaction
Longitudinal waves
Wavelength
Frequency = Pitch
Hertz Hz
20 – 20,000 Hz
Ear (outer, middle, inner ear)
Amplitude = Loudness = Volume
Decibels dB
Sonar
Ultrasound, infrasound
Other waves
•
•
•
•
•
Transverse waves
Crests
Troughs
Electromagnetic waves
Water waves
That’s all folks!