Puretone Audiometry

Threshold

Lowest level of a puretone that a person reliably responds to at least 50% of the time

quiet

PT thresholds are obtained in a _____ environment for specified frequencies

perceived as pitch

puretone frequency is _______ ___ ___

• low, mid, high

20-20,000 Hz

what frequencies are humans most sensitive?

250-8000 Hz, measuring where speech sounds fall

where do audiologists typically measure in Hz? why?

why do audiologists use puretone thresholds?

• describe the degree of hearing loss

• determine the location of the hearing loss

• determine need for medical referral

• predict how hearing loss may affect listening and communication abilities

• cross-check of other audiometric findings

sound booth

• specially designed sound-attenuating room

• increase sound absorption (no echos) 

• reduce sound reflection

inability to read facial expressions

con of having patients keep their back to the audiologist while testing

make sure they are staying on task, maintain eye contact to keep attention

why is it helpful to have peds facing audiologist during testing?

allows for seeing facial expressions while avoiding awkward eye contact

why does professor prefer side profile when testing?

visual cue

avoid giving these, as it could muddle results and lead to inaccurate confirmations of having heard the tone

inadvertent cues

• hand, head, eye movements

• facial expressions

• visible reflections

audiometer

electronic or computer-based instrument used for behavioral audiometric evaluations

transducer

instrument that converts energy from one type to the other

insert earphones

• proper placement: outer edge just within first bend of ear canal

• held in place by foam cuff, compress cuff prior to insertion into the ear canal

• single use - replace for each patient

insert earphone pros

• reduces background noise

• reduces need for masking

they are single-use, making them more expensive

given the pros of insert earphones, why aren’t they used all the time in audiology clinics?

supra-aural earphones

• proper placement: align center of earphones with opening of ear canal

• held in place with headband, designed to maintain tension

• cleaned between each patient

supra-aural earphones pros

• testing those with atresia

• profound hearing loss

• allows for testing with those with active drainage from ears

cicumaural earphones

• also known as extended frequency (EHF) earphones

• designed to test frequencies > 8000 Hz

• covers the entire ear - positioned around the pinna

circumaural earphones pros

• EHF testing

• ototoxic monitoring

• noise induced hearing loss monitoring

soundfield speakers

used for testing:

• patients who will not tolerate head/earphones

• patients wearing hearing aids / cochlear implants (aided testing)

soundfield speakers limitation

• both ears receive the sound

• not possible to get ear specific information

bone conduction vibrator (oscillator)

• plastic casing that is set into vibration by puretone

• delivers puretone mechanically to the skull

• stimulates inner ear

• proper placement: on the mastoid bone (behind the ear) / forehead

• held in place with headband with tension

• should NOT touch the pinna, would cause tactile response

• placed under hair

conductive portion

• outer ear

• middle ear

sensorineural portion

• inner nerve

• 8th nerve

• central system

air conduction

mode of sound presentation through earphones:

• supra-aural

• inserts

• circumaural

• soundfield speakers

entire auditory pathway

air conduction stimulates the _______ _____ ______

• outer → middle → inner

degree of hearing loss

what does air conduction measure?

bone conduction

• mode of sound presentation through bone oscillator

• stimulates sensorineural portion only

• bypasses conductive (outer and middle ear) portion of auditory pathway

type of hearing loss

what does bone conduction measure?

air-bone gap

difference between air conduction threshold and bone conduction threshold

sensorineural portion affected

air-bone gap difference ≤ 10 =

conductive portion affected

air-bone gap difference > 10

puretone threshold testing

• introduce yourself and wash / sanitize hands

• perform otoscopy FIRST always

• provide clear instructions for PT testing (faintest level of sound, mode of response such as raising hand, pressing button, saying yes, etc.)

• test AC before BC

• place transducer on the patient

puretone presentation

• present tone by pressing and releasing presentation button

• steady tone, pulsed tone, warble tone

1-2

presentations of puretones should be _____ seconds in duration

variable pauses

1-4 second breaks between presentations to avoid a predictable rhythm

modified hughson-westlake procedure

• commonly referred to as the “down-10 up-5” bracketing procedure

• start at 30 dB HL

• no response? increase 20 dB until they respond

• patient decrease by 10 dB until there is no response

• increase tone by 5 dB until they respond

• continue using down 10 dB and up to 5 dB until you obtain threshold

• two responses out of three presentations at a single level

air conduction frequencies

• 1000

• 2000

• 3000*

• 4000

• 8000

• retest 1000

• 500

• 250

bone conduction frequencies

• 1000

• 2000

• 3000*

• 4000

• 500

• 250*

interoctave frequencies

tested if ≥ 20 dB difference between adjacent frequencies

ac: 750, 1500, 3000, 6000

bc: 750, 1500, 3000

hearing screen

select number of frequencies presented at one level

• typically 500, 1000, 2000, and 4000 Hz at 20 dB

• pass / refer

hearing threshold

detects the softest sound that can be heard by an individual, can provide more diagnostic information overall

test-retest reliability

± 5 dB acceptable and expected

false negative

patient does not respond to signal that was heard

say: “listen carefully and push the button even for the faintest sound”

false positive

patient responds when no signal presented

say: “make sure you only push the button when you hear a tone”

patiral responses

• patient cocks their head

• patient has a facial expression conveying they heard a tone

• holding up hand partway / “hovering” thumb over button

• say: “go ahead and raise your hand all the way up even if you think you hear the sound” 

• caution: may lead to more false positives

warble tones, narrow band noises

utilized instead of puretones for pediatric and difficult-to-test populations

conditioned-play audiometry (CPA), visual reinforcement audiometry (VRA)

utilized instead of conventional audiometry, most often for children