hearing assessments and hearing aids Flashcards
what is pure tone audiometry
the most commonly performed test in audiology that determines hearing sensitivity at different dB and frequencies
what frequencies are affected more by ototoxic medication
higher frequencies affected first
R ear vs L ear colour and symbol in audiogram
R ear - red circle
L ear - blue X
what are the different dB ranges of hearing loss (mild, moderate, severe, profound)
normal: -10-20 dB
mild: 20-40 dB
moderate: 40-70 dB
severe: 70-100 dB
profound: 100-120 dB
what does a typical presbycusis audiogram look like
bilateral hearing loss that decreases linearly at higher frequencies (see lect)
what is the issue with bone conduction testing
either ear could be generating the response and so it is difficult to tell which ear is defective -> sound emitter is usually placed behind the ear of interest to try and omit this
what does an air-bone conduction gap on an audiogram indicate
conductive hearing loss - sounds can be heard at a much lower dB through bone compared to air indicating a defect in sound conduction rather than a neural problem
what will a sensorineural hearing loss look like on an audiogram
hearing loss via both air and bone conduction tests -> it is the nerve that is affected so sounds are not being transmitted
what does a mixed hearing loss appear like on an audiogram
bone conduction is better than air but bone is still not within the usual range
what is masking (audiology)
a method employed to stop compensation by a better hearing hear when testing hearing loss - a narrowband noise is played in the good ear so that it cannot compensate for the bad ear
what is the symbol for masking on audiogram
[ or ]
what is tympanometry
a test that measures the change in compliance (movement) of the eardrum
what is normal middle ear pressure
+50 to -50 daPa
what is a normal ear canal volume
no normal volume but > 3 cm^3 usually indicates perforation, can also be increased by interventions such as grommets
what does a peaked 0daPa tympanometry classification indicate
normal middle ear function - movesthe most when air pressure is equal on both sides
what does no peak in tympanometry indicate
lack of movement of ear drum -> glue ear if ear canal volume is normal, gommets or perforation is large ear canal volume
what does a peak at negative pressure in tympanometry indicate
eustachian tube dysfunction
what happens to middle ear pressure in eustachian tube dysfunction
pressure increases due to blockage of the tube
what are the 2 newborn baby hearing screens
- well baby pathway - otoacoustic emission test (OAE) measures hair cell function in the inner ear, a sound is playedand the cochlear produces and echo
- NICU protocol - the auditory brainstem response (ARB) is a non-invasive test that uses electrodes to measure how well sounds reach your baby’s brainstem, baby must be asleep to stop the minute changes being hidden
why do NICU babies need a different hearing test
they have a higher chance of neuropathy affecting their hearing and so hearing must be tested to the level of lateral lemniscus (part of the auditory tract of the brainstem)
what are the 3 main parts in a hearing aid
- hearing aid
- tubing
- earmould/tip - custom made
disadvantages of open fit hearing aids
- more feedback
- needs to be cleaned out
- fiddly and harder to put in if poor dexterity
disadvantages of receiver in ear canal hearing aids
- infection
- ear wax
- water can get in and damage it
how does anchored hearing aid work
sound is transmitted through the skull -> used in patients with permanent conductive hearing loss or who cannot use standard hearing aids e.g. those who have not developed an ear canal
how does a cochlear implant work (3)
- The processor (external) captures sound signals and sends them to a receiver implanted under the skin behind the ear
- The receiver sends the signals to electrodes implanted in the cochlea
- The signals stimulate the auditory nerve, which then directs the signals to the brain
how do CROS hearing aids work
used when there is one hearing and one non-hearing hear
1. A hearing aid for the deaf ear consists of a microphone (to pick up sounds on the deaf side) and a transmitter, which transmits sounds to the other ear
2. The transmitter sends the recorded sounds through radio waves to the hearing aid in your healthy ear
3. This second part of the CROS system consists of a radio receiver for wireless communication and an amplifier, The latter amplifies the sounds received from the other side
how can vestibular dysfunction be assessed (3)
- dix-hallpike
- gait assessment
- calorics - pour cold/hot water in one ear in order to establish a temperature gradient from one side of the canal to the other, this should induce dizziness in the pt and nystagmus should be seen, absence of this indicates defect
