TUNING FORK TESTS
Simple accurate at dividing hearing into AC & BC
about 100 years old; ENTs still rely on them
each fork has C octave pitch: 256, 512, 1024, 2048 Hz
lower Hz’s more commonly used; eg. Bing test; Schwabach & Rinne tests might use higher Hz’s
Tuning fork tests good at telling nature (type or quality) of HL
not good at numerically describing degree (quantity) of HL
tuning fork intensity not well controlled; depends on how hard you hit it (varies by 30 dB)
audiometers much better for quantifying AC, BC, & air-bone gaps in terms of decibels
Schwabach test
Quantitative test of BC
compares client’s HL to examiner’s HL; assumes examiner has normal HL
Procedure
place tuning fork on client’s mastoid bone; when client no longer hears tone, put behind own ear
count seconds tone audible after client stops hearing tone
Normal schwabach: both stop hearing tone at same time
diminished schwabach: client stops hearing tone before examiner (SNHL)
prolonged schwabach: client hears tone longer than examiner (conductive HL)
Rinne test
Compares client’s own HL by AC & BC (client serves as own control)
eloquent demonstration of how middle ear serves to increase sound pressure
Procedure
ask client which tone loudest when: fork next to outer ear or when fork held against mastoid
normal HL should hear tone louder when fork at outer ear; AC more efficient than BC
because middle ear amplifies sound
Positive rinne: tone louder by AC (normal HL or SNHL)
negative rinne: tone louder by BC (fair degree of conductive HL)
false negative rinne: cochlea not tested responds to tone
Bing test
Based on occlusion effect: loudness of BC sound increases when ear plugged
review reasons why occlusion effect occurs
effect most prominent with low-frequency sounds
Procedure
place tuning fork on mastoid
compare client’s own HL when ear canal repeatedly opened and closed
Occlusion effect present: normal HL or SNHL
occlusion effect absent w/ middle ear pathology b/c it blocks sound from entering cochlea
Weber test
Test of lateralization based on Stenger effect
if tone sent to both ears simultaneously, client hears only loudest one
Procedure
tuning fork placed on center forehead or front teeth
client states where tone heard: right, left, center
Midline sensation: normal HL, equal conductive or SNHL in both ears
tone heard in better ear: SNHL in bad ear; Obviously, BC picked by better cochlea
tone heard in worse ear: conductive HL in bad ear; Why is this?
Not due to Occlusion Effect; this is an outer ear canal phenomenon
ear w/conductive HL receives input from BC and not AC
normal ear hears competing ambient room noise while cond HL ear does not