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Sound Waves
SOUND WAVES ARE LONGITUDINAL (IN SOUND
WAVES, THE VIBRATIONS OF AIR MOLECULES ARE
PARALLEL TO THE DIRECTION OF WAVE MOTION.)
Vibrating
objects
THE PRODUCTION OF SOUND WAVES:
Sound
is produced when something
vibrates.
The vibrating body causes the medium
(water, air, etc.) around it to vibrate.
Sound waves consist of areas of high and
low pressure called compressions and
rarefactions, respectively.
 Compression:
the part of a longitudinal wave in
which the density and pressure are at a
maximum.
 Rarefaction:
the part of a longitudinal wave in
which the density and pressure are at a
minimum
 Sound
waves actually travel away from a
vibrating source in all three dimensions
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CHARACTERISTICS OF SOUND WAVES
Speed of sound depends on:
1. The state of the medium
1. The state of the medium
Sound waves can travel through solids, liquids, and
gases. Because waves consist of particle vibrations.
The speed of a wave depends on how quickly one
particle can transfer its motion to another particle.
Why???
2. The temperature of the
medium
2. The temperature of the medium.
IN GAS
IN LIQUIDS AND SOLIDS
Disturbance can spread
The particles are close
faster at higher temperatures
enough together that the
than at lower temperatures.
difference due to
temperature changes is less
noticeable.
Sound pitch
•Pitch is a term used to describe how high or low
a sound is.
•The pitch of a sound depends on the frequency
of the source of the sound.
•A high frequency produces a high pitched sound.
• A low frequency produces a low pitched sound.
Frequency increases, pitch increases
Loudness
•Loudness depends on the amplitude of the sound
wave.
•The larger the amplitude the more energy the
sound wave contains therefore the louder the
sound.
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The Doppler Effect

The Doppler Effect is the change in frequency of a sound wave for
an observer moving relative to its source.

The frequency of the sound waves increases directly when it is
closer to an object. As the frequency of sound waves increases,
the pitch we hear increases as well.

This results in a higher pitch which easier to hear.

The frequency decreases as the object moves away from the
listener, who hears a decreasing pitch.
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