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Sound
• Sound, like light, comes in waves
• Sound is vibration
• Features of sound include:
–Pitch
–Hertz
–decibels
Pitch
• A sound’s highness or lowness
• Dependent on the frequency of the sound wave – the more “waves per second” the higher the frequency or pitch
• Is measured as hertz (Hz)
Hertz (Hz)
• A measure of the number of sound wave peaks per second; measures “frequency”
• Determines the pitch of the sound
• One Hertz = one vibration per second
Low Pitch
• Wave peaks are far apart
Human hearing goes from 20 Hz to 20,000 Hz although some ears (and speakers) are
better than others
High Pitch
• As pitch increases, so do the number of waves
Remember - Human hearing goes from 20 Hz to 20,000 Hz note: a kilohertz is 1,000 hertz
so 20 kilohertz equals 20,000 hertz
Decibel (dB)
• A measure of the height of the sound wave
• Determines the loudness of the sound
• Sometimes called amplitude
Break It Down
• Sound waves are collected in the outer ear, amplified in the middle ear, and transduced, in the inner ear.
PINNA
• It collects sound and directs it into the outer ear canal.
The visible part of the outer
ear.
• The opening through which sound waves travel as they move into the ear for processing
• Ends at the eardrum
Auditory Canal
Eardrum
•Also called the tympanic membrane. A thin membrane that vibrates when sound waves reach it.
• it transfers sound vibration from the air to the tiny bones of the middle ear
•Can be damaged by objects in the ear or exceptionally loud noises
Bones of the middle ear - Ossicles
•Three tiny bones that transfer sound waves from the eardrum to the cochlea
•Hammer, anvil and stirrup–Fun fact: the stirrup is the smallest bone in the human body – only .25 cm
Oval Window•The point on the surface of
the cochlea which receives the sound vibration from the bones of the middle ear (ossicles)
•As the oval window vibrates, the fluid in the cochlea vibrates.
Cochlea
•A hearing organ where sound waves are changed into neural impulses (transduction)
•The major organ of hearing•Filled with fluid; a snail
shaped body tube
Hair Cells• The receptor cells for hearing in the
cochlea that change sound vibrations into neural impulses
• Transduction!
Auditory Nerve
• The nerve that carries sound information from the ears to the temporal lobes of the brain
Divisions of the Ear
• Ear’s structure can be divided into:
–The outer ear
–The middle ear
–The inner ear
REVIEW
• Sound comes into the ear • Goes through the ear canal to the
eardrum• Ear drum changes sound into
vibrations• Vibrations go through middle ear
to the inner ear –
REVIEW
• Where vibrations are changed into neural impulses so that the brain can read / interpret the sound –
• What are the receptors cells for hearing?
Problems with hearing• Conduction deafness* (middle ear damage)
• Nerve deafness (hair cell or auditory nerve damage)
Localization of Sound
• Locating where sound is originating from
• Done through two cues:
–Which ear hears the sound first?
–Which ear hears the louder sound?
Vestibular Sense• The system for sensing body
orientation and balance• Relies on fluid in the semicircular
canals of the inner ear• Spinning in circles disrupts the
fluid.
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