Case 4 - How we do it and what goes wrong

Question 1

what does 0dB mean

Answer 1

does not mean no sound at all it just means sound pressure level

Question 2

what is frequency measured in and what is normal

Answer 2

measured in Hz
- 20-20000Hz is normal

Question 3

what is speech in Hz

Answer 3

200-500Hz

Question 4

size of the external ear canal

Answer 4

one inch tube with 7mm diameter

Question 5

how much does sound increase by when going down the external ear canal

Answer 5

10-20dB

Question 6

what is the main function of the external ear

Answer 6

to protect the delicate ear drum but as with any hole it can collect debris and moisture which would encourage bacteria growth

Question 7

how does ear canal skin grow

Answer 7

seems to migrate, grow like fingernails so ear canal is almost like a converyor belt

Question 8

what type of wax do caucasians and black people have

Answer 8

honey wax

Question 9

what kind of wax do asians have

Answer 9

flaky wax

Question 10

what is the universal quality of wax

Answer 10

it is waterproof

Question 11

how is the middle ear ventilated

Answer 11

at atmospheric pressure: physiological gas exchange across the mucosa
at abnormal pressure: eustachian tube opening - in emergency to prevent out ears from busting

Question 12

air:

Answer 12

low pressure high-displacement vibration

Question 13

cochlear fluids:

Answer 13

high pressure low-displacement vibration

Question 14

what starts the vibrations of the occicles

Answer 14

the malleus

Question 15

how long is the malleus handle

Answer 15

longer than the incus long process

Question 16

what is the tympanic membrane

Answer 16

a mechanical level

Question 17

what happens when there is stiffening of the ossicles

Answer 17

makes us more deaf nd protecting the inner ear from noise damage

Question 18

how long can we tense for

Answer 18

40 minutes

Question 19

how is the stapedius stimulated

Answer 19

acoustically.

Question 20

what happens when sound reaches the oval window

Answer 20

it vibrates and sets up a wave in the perilymph fluid

Question 21

where does this fluid go

Answer 21

travels the two and a half turns of the cochlear and washes up on the round window

Question 22

what did Kemp find

Answer 22

that the outer hair cells were in fact a muscular function, not for hearing
when the basilar membrane vibrated with sound, the outer hair cell muscles would tense the tectorial membrane and this would focus the resonant frequency of the basal membrane so that you could hear the difference between smaller changes in frequency

if the cochlea was poisoned, in other words if the outer hair cells died, then the cochlea could only sense a change in 50Hz frequency

Question 23

what is the rigid resonating structure made form

Answer 23

the basilar membrane, the tectorial membrane and oCHs

Question 24

what do IHCs sense

Answer 24

orignal sense of sound and depolarise when the hair moves to angstroms In fluid movement inside the organ od corti.

Question 25

when would fine tuning be removed

Answer 25

OHC death

Question 26

what does conductive hearing impairment involve

Answer 26

the external and middle ear while conduct sound to the cochlea

Question 27

what does sensorineural impairment involve

Answer 27

the sensation of hearing sound in the cochlea and the associated nerve pathway to the brain

Question 28

what infection makes the external ear hot and inflamed

Answer 28

perichondritis makes the ear hot and inflamed and is usually due to pseudomonas aeruginosa and as soon as the external ear canal is cut off conductive hearing impairment will result.

if you have a perforation of the tympanic membrane, this will cause a conductive hearing impairment

Question 29

what would fluid behind the eardrum cause

Answer 29

conductive impairment

Question 30

percentage of children who recover after 3 months having grommets

Answer 30

50%

Question 31

what do the other 50% have

Answer 31

• hearing loss
• speech delay
• educational impairment

Question 32

what can conductive hearing impairment also be caused by

Answer 32

abnormalities of the ossicles
- severe head injury
- eroded away in infection
- otosclerosis

Question 33

what is the most well known cause of neurosensory hearing loss

Answer 33

acoustic neuroma which is a benign tumour on the cochlear nerve