Hearing Test

• http://www.freemosquitoringtones.org/hearing_test/

Audition: Hearing

• As with the eye, the ear receives waves, this time of sounds.

• Length of wave = pitch

• height of wave (amplitude) = volume

Volume• Volume measured in decibels.

– Every 10 point increase equals a 10 times rise in level.

• Frequent exposure to 85+ = possible deafness– A busy street corner– 85 decibels is a trillion times louder than

the lowest threshold for hearing sound.

The Ear• Outer ear funnels waves into auditory canal

to the tympanic membrane – Tympanic membrane = Eardrum = tight vibrating

membrane • Tympanic membrane attached to bones of

the middle ear called ossicles– the hammer, anvil, and stirrup = piston

movement• The bones are attached to the Cochlea in the

inner ear through the oval window.– The Cochlea is to hearing what the retina is to

seeing: the receptor.

Pinna

• External visible flap of skin and cartilage

Auditory Canal

• Part of outer ear along with pinna, leads to tympanic membrane

Tympanic Membrane

• Also called eardrum• Separates outer ear from middle ear and

vibrates with reception of sound

Ossicles

• Three bones in middle ear (malleus/incus/stapes or hammer/anvil/stirrup)

• Set in motion by eardrum that transmit sound vibrations to the cochlea

Cochlea

• Basilar membrane: subject to pressure changes in cochlear fluid– Contains the organ of Corti – an organ that

contains auditory sensory cells (hair)• Hair Cells: organ of Corti deflected by fluid

movement trigger neural impulses to the brain via auditory nerve

Basilar Membrane:

Amber fields of grain…

The Cochlea – how it works• When the bones of the middle ear

shake (piston) the cochlea’s oval window, it makes the liquid inside ripple which, in turn, vibrates the hairs embedded in the basilar membrane.

• This vibrating creates the action potential.

Hair cells of inner ear, can be damaged by age and loud noise, particularly bass sounds.

Pitch Theories• Place theory: high pitches are

created by where on the basilar membrane the liquid vibrates the hairs. –The brain reads the place and

makes you hear the corresponding pitch. (high pitches)

Pitch theories cont’d

• Frequency Theory: brain reads amount of times per second the hair vibrates and interprets to determine low or high pitches.

Sound location• Your brain uses a combination of visual

cues and sound cues to determine sound location. (parallel processing).

• The sound cues are the level of amplitude that each ear receives. The visual cues can fool you, like with a ventriloquist’s dummy. (dichotic listening test)

Deafness• Conduction Deafness: Caused by damage to the ear drum

or middle ear bones. – Hearing aids can help by increasing the amount of sound waves

to the cochlea.

• Sensorineural Deafness (Nerve Deafness): caused by damage to the hairs by repeated exposure to loud noises or disease. – Rarely helped by hearing aids. Possible in the future by cochlea

transplants.– http://www.youtube.com/watch?v

=ZT7sxr9t3Qg&feature=related

Perception and Attention Change

• Incoming information more important due to lack of auditory input– Deaf people tend to take in visual inputs more

than most (i.e. ability to read lips)

Hearing loss

• Tends to be in the higher pitch ranges. Makes it hard to pick out foreground from background. Higher frequency hairs are at beginning of cochlea

• If can’t talk over sound.• If others can hear your IPOD• If ringing in the ears.