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IPC Notes
Sound
The Nature of Sound
Sound waves are caused by
vibrations of molecules that travel
in the form of compressional
waves.
Factors that Affect the Speed of Sound
Sound travels faster in solids
because the particles are closer
together.
Sound travels faster at higher
temperatures because of the
kinetic theory of matter.
Human Hearing
Sound waves travel through the
ear canal and transfer vibrations
to the ear drum.
Human Hearing
Sound is then transferred to the
middle ear where 3 small bones
(the hammer, anvil & stirrup)
amplify the force of the sound.
Human Hearing
Finally, the inner ear converts the
sound waves into nerve impulses
which are sent from the auditory
nerve to the brain.
Ear Diagram
Properties of Sound
intensity – the amount of energy
of the wave
loudness – the human perception
of sound intensity; sounds with
over 120 decibels can cause pain
Properties of Sound
frequency – the measure of how
many wavelengths pass a particular
point each second
Humans can typically hear between
20-20,000 Hz of frequency.
Properties of Sound
ultrasonic – wave frequencies over
20,000 Hz; aka: supersonic
infrasonic – wave frequencies less
than 20 Hz; aka: subsonic
Properties of Sound
pitch – how high or low a sound is
ex) nails on a chalkboard = high pitch
a bass drum = low pitch
Properties of Sound
The Doppler Effect is an apparent
change in pitch due to the motion of an
observer or a sound source.
ex) a police siren sounds higher pitched
as it approaches you and lower pitch as
it drives away