Ear Flashcards
outer ear
(the part you can see) opens into the ear canal
inner ear
contains the auditory (hearing) nerve, which leads to the brain.
middle ear
the eardrum separates the ear canal from the middle ear. Small bones in the middle ear help transfer sound to the inner ear
how do you hear
Any source of sound sends vibrations or sound waves into the air. These funnel through the ear opening, down the ear, canal, and strike your eardrum, causing it to vibrate. The vibrations are passed to the small bones of the middle ear, which transmit them to the hearing nerve in the inner ear. Here, the vibrations become nerve impulses and go directly to the brain, which interprets the impulses as sound.
pinna
the outer part of the ear, serves to “catch” the sound waves. It also helps you determine the direction of a sound. Your brain determines the horizontal position of a sound by comparing the information coming from your two ears.
tympanic membrane or eardrum.
This is a thin, cone-shaped piece of skin, about 10 millimeters (0.4 inches) wide. It is positioned between the ear canal and the middle ear. Air from the atmosphere flows in from your outer ear onto one side and from your mouth on the other (the middle ear is connected to the throat via the eustachian tube) so the air pressure on both sides of the eardrum remains equal. This pressure balance lets your eardrum move freely back and forth with even the slightest air-pressure fluctuations.
malleus
hammer
inus
anvil
stapes
stirrup
ossicles amplify the force from the eardrum in two ways
The main amplification comes from the size difference between the eardrum and the stirrup. The eardrum has a surface area of approximately 55 square millimeters, while the faceplate of the stapes has a surface area of about 3.2 square millimeters.
configuration of ossicles provides additional amplification. The malleus is longer than the incus, forming a basic lever between the eardrum and the stapes.
cochlea
(hair like cells)
This pressure amplification is enough to pass the sound information on to the inner ear, where it is translated into nerve impulses the brain can understand by the cochlea
Age-related hearing loss (presbycusis)
Gradual onset
Noise-induced hearing loss
being with machinery all day
dips at one frequency
human hearing range
20-20000Hz
ear drum [or tympanic membrane}
It transfers sound waves from the outer ear to the ossicles of the middle ear
ossicles [or bones of the middle ear]
They are a system of levers with a mechanical advantage (of 1.5) [or amplification]
which links two membranes (ear drum and oval window) or transmits sound vibrations from outer to inner ear]
windows: oval and round
These allow sound vibrations to enter the fluid of the inner ear
OR
allow sound vibrations to be transmitted around the cochlea
OR
contain the inner ear’s fluid while allowing the fluid to move
cochlea
This converts (pressure) waves [or vibrations] in the fluid into electrical signals
OR
stimulates (auditory) nerves to send signals to the brain
State what is meant by the threshold of hearing and state the frequency at which the reference threshold is quoted.
The threshold of hearing is the lowest intensity of sound that can be detected by the human ear. The reference intensity (1.0 × 10–12 W m–2) is taken at 1 kHz
Sound intensity levels are usually measured in decibels. Give two reasons why this logarithmic scale is used.
=The ear has a logarithmic response OR the log scale is chosen to match the (perceived) response of the ear,
=It is needed to accommodate very wide range of sound intensities to which ear can respond
=The perceived change in loudness is proportional to fractional change in intensity
=Ten-fold increases in intensity are perceived as steps of equal increase in loudness
=The log scale means that numerical values on the scale represent ratios of two sounds, expressed as the log of that ratio
why was it necessary to introduce an adapted scale referred to as the dBA scale, which is used on some sound level matters
The dBA scale takes account of the frequency dependence of the sensitivity of the ear
OR to match the ear’s frequency response or meters calibrated on a dBA scale to give frequency-weighted readings
State two reasons why the logarithmic dB scale is used to compare sounds of different intensities
The ear has logarithmic response as this accommodates wide range of intensities
Another scale used to compare sounds of different intensities is the dBA scale. What are the main differences between the dBA and the dB scales?
The dB scale has a flat response with frequency whereas the dBA scale is frequency compensated. this measn that for dBA, threshold intensities are different for different frequencies
what does the ossicles do?
These are a system of levers to multiply the force
OR system of levers to link outer and inner ear
State what is meant by attenuation and what causes it
Attenuation is the reduction in intensity/energy/power of the wave as it travels through a medium. This is due to absorption/scattering/diffraction.
State the main difference between the dB scale and the adapted dBA scale used to measure sound intensity levels.
The dBA scale is frequency dependent whereas the dB scale is not
A patient has a hearing test to obtain an equal loudness curve at a level above the threshold of hearing.
Describe how such a curve is obtained
The patient must listen to a sound at a frequency of1 kHz and an intensity level of 10 dB. That is the ‘loudness’ that is to be used as the reference level for the test. The patinet must the listen to a sound at a different frequency and the lintensity level must be adjusted until the patient says the loudness is the same as the reference one. This is then repeated for several frequencies between 20 Hz and 20 kHz to obtain the curve.
State the frequency of sound at which the normal ear is most sensitive.
3 kHz
State the main features of hearing loss in terms of frequency response for age-related hearing loss
A sound level perception curve steadily decreases towards higher frequencies - as frequency increases the loss increases
State the main features of hearing loss in terms of frequency response for noise-related hearing loss
There is a ‘dip’ in a sound level perception curve at about 4 kHz - loss is concentrated around 4 kHz
