Pure tone audiometry Flashcards
Reliability is dependent on:
- calibration
- test environment
- pt perfomance
- examiner sophistication
What is dB HL?
- The average loudness across frequencies for the average person to JUST detect a sound
- Reference for hearing is changed to the average of a group of normal hearing adults
- softest sounds become 0 dB HL
Audiometer
- tests hearing SENSITIVITY by AC and BC
- most test up to 8000 Hz (for speech)
- tones are attenuated
On the audiogram, lower down = ______ hearing loss
MORE hearing loss
Attenuator
- there is a max electrical force you set a transducer at, and a max output the transducer can give.. so it attenuates the signal to a certain level
3 transducers of an audiometer
- earphone
- speaker
- bone
Two types of earphones
- TDH (supra-aural)
- ER-3A (insert)
What happens if you turn up the AC all the way
- you can cause damage to the patient
Can you damage someone’s hearing using BC?
No
2 ways around getting rid of background noise
- insert earphones (but if you use w/ BC and inserts still in, you get occlusion effect so take them out first)
- sound-isolated chamber, to keep noise in room below level of masking that would cause a threshold shift
Threshold of hearing sensitivity
- the lowest level needed for a person to detect the presence of a signal 50% of the time
- level at which the tone is barely audible
What does AC audiometry test?
- what is the patient’s hearing sensitivity across freqs?
- it’s about DETECTION
What info do we get from AC audiometry?
- degree of hearing loss (not type) b/c it tests the WHOLE SYSTEM
Rule of thumb for Hughson-westlake method
- down 10, up 5
Normal hearing dB range for adults
- 10-25 (10-15 for kids) dB
Slight hearing loss for kids
- 15-25 dB
Mild hearing loss
- 25-40 dB
Moderate hearing loss
- 40-55 dB
Moderately severe hearing loss
- 55-70 dB
Severe hearing loss
- 70-90 dB
Profound hearing loss
- 90+ dB
What is masking
- controlling for interaural attenuation by putting a range of noise around the centre frequency you’re testing, on the ear you’re NOT testing
Why do we mask
- if you keep turning up a sound, eventually it will be loud enough to vibrate the skull and the sound will be picked up by the opposite ear (interaural attenuation)
What dB level do we start to mask at
40 dB (AC) 10 dB (BC)
Why do we do BC audiometry?
- to determine the hearing levels at the cochlea
where do we place the BC
- mastoid
What is sensorineural hearing loss?
- no air-bone gap
- no conductive component
- problem in inner ear or beyond
What is conductive hearing loss?
- air-bone gap
- BC better than AC
- BC w/in normal range
- AC outside normal
- problem in transmitting signal from outer ear to inner ear
What is mixed hearing loss?
- Air-bone gap
- BC better than AC
- BC outside normal range
- AC worse
