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Hearing
Subtitle
I CAN
• Explain the sensation process as it applies
to hearing using the anatomically correct
terms
The Physics of Sound
Frequency: The
number of cycles a
Amplitude: sound wave completes
the Strength in a given period of time
of a wave
Anatomy of the Ear
From Sound Wave to Perception
1. Pinna Tympanic Membrane (eardrum)
bones of inner ear (hammer, anvil,
stirrup) COCHLEA (primary hearing
organ)
2. Cochlea is filled w/ fluid, which further
transmits vibrations to thin membraneBasilar Membrane
3. BM = Transduction; tiny hairs on BM tickle
the sensory nerves
4. Neural message is sent to Temporal Lobe
How Sound Waves Become
Auditory Sensations
Tympanic membrane –
The eardrum
Copyright © Allyn and Bacon 2006
How Sound Waves Become
Auditory Sensations
Cochlea –
Where sound
waves are
transduced
Copyright © Allyn and Bacon 2006
How Sound Waves Become
Auditory Sensations
Auditory nerve –
Neural pathway
connecting the ear
and the brain
Copyright © Allyn and Bacon 2006
3 Psychological Sensations of
Sound
1.Pitch- the way we sense
frequency
2.Loudness- the way we
sense amplitude
3.Timbre- the way we
sense the complex mix of
tone
Copyright © Allyn and Bacon 2006
Theories of Hearing
• Place theory
– Pitch (how high or low something is) is determined by location of
vibration along the basilar membrane
– But this doesn’t explain low-pitch since we haven’t found specific
positions for those on the bm
• Frequency theory
– Pitch is determined by frequency hair cells produce action
potentials
– If the frequency of the sound is 100 waves per second then the
neuron fires at 100 pulses per second.
– But we can hear frequencies above 1000 waves per second but
can’t fire neurons faster than 1000 pulses per second.
– Volley Principle
• Pattern of sequential firing creates a combined high frequency
signal
Localization of Sounds
Because we have two ears, sounds that reach
one ear faster than the other ear cause us to
localize the sound.
Conduction Deafness
• An inability to hear resulting from damage to
structures of the middle or inner ear
• Conductive hearing loss is often only mild and is
never worse than a moderate impairment.
• Generally, with pure conductive hearing loss, the quality
of hearing (speech discrimination) is good, as long as
the sound is amplified loud enough to be easily heard.
• Possible Causes
• Ear wax build up
• Fluid inside the inner ear, like from an inner ear
infection.
• If the bones of the ear get a buildup of calcium
Sensorineural Deafness… or
Nerve Deafness
• An inability to hear, linked to a deficit
in the body’s ability to transmit
impulses from the cochlea to the
brain, usually involving the auditory
nerve or higher auditory processing
centers
• It can be mild, moderate, severe, or profound,
to the point of total deafness.
• Possible Causes
• Long-term exposure to environmental noise
• Genetic
• Disease or illness
• Medications
• Physical trauma
Pre-Lingual Deafness
• These are people that are born deaf
CAN I?
• Explain the sensation process as it applies
to hearing using the anatomically correct
terms