audiogram
graph where pure tones results are recorded
x axis audiogram
frequency
y axis audiogram
intensity
20 dB change along y axis corresponds to
doubling of frequency
0 dB HL line represents what
lowest normal hearing level for each frequency averaged across normal hearing listeners
difficult to use dB SPL scale clinically because
the same amount of hearing loss at different frequencies would be represented by diff values in dB SPL and the lines on the audiogram would not be linear
to simplify representation of hearing loss across frequency range:
- minimum audibility curve is normalized
- we want same amount of hearing loss to look equal on audiogram
- dB HL tells exactly how many dB a threshold is above average normal hearing
dB HL to SPL
add reference number
dB SPL to HL
subtract reference number
dB HL scale
directly represents how many dB a test signal is above the normal hearing threshold at each frequency
useful to know how to do dB HL/dB SPL conversions
sound level meter, hearing aid fittings, literature/research
air conduction thresholds unmasked
O = right AC
X = left AC
bone conduction thresholds unmasked
< = right
> = left
why is there need for masking
when testing specific ear, need to be sure that results are from that ear only
masking
the process of putting noise into the NTE while measuring thresholds in TE; test procedure
masker
the noise presented to the NTE; NBN (narrow band noise)
Masked thresholds
the pure tone thresholds obtained (in the TE) (when masking has been used in the NTE)
masked air conduction
△ - AC masked right
▢ - AC masked left
masked bone conduction
[ - BC masked right
] - BC masked left
