Appendix D Pass/Refer Criteria For Teoae - Maico ERO SCAN Operating Instructions Manual

TM
Operating Instructions ERO SCAN Screener

Appendix D Pass/Refer Criteria for TEOAE

The same basic principles that underlie DPOAE Pass/Fail criteria underlie TEOAE
Pass/Fail criteria. In the case of transients, requiring SNR of 4 dB at any three
out of the six test frequencies drops the probability of passing an ear with a
significant hearing loss to less than 1%.
Note: The SNR limits for transients are lower than the corresponding limits for
distortion products primarily because the traditional noise calculation used in
TM
TEOAE measurements (and in the ERO•SCAN Screener instrument) gives a 3
dB lower SNR than the calculation used for DPOAEs. Without that difference,
the numerical SNR value for a PASS with the two methods would be quite
similar.
TM
The ERO•SCAN Screener uses a novel noise-rejection algorithm (patent
pending) that permits accurate DPOAE and TEOAE measurements in
background noise and babble as high as 55-65 dB SPL (A-weighted). Briefly
TM
explained, use of available memory in the ERO•SCAN Screener processor
permits a post-hoc statistical analysis that identifies those samples whose
retention would improve the overall accuracy. Those samples are included in
the final analysis; the noisier samples are rejected.
The improved operation in noise with the new algorithm was so substantial
that we conducted a complete replica of our original validation tests in "fully
impaired ear" cavities and were able to verify that no increase in false
negatives (false passes) was introduced. Under no test conditions was any such
degradation uncovered.
The artifact rejection can only reject the noisiest samples in a measurement
period. If the ambient noise level rises too high (and/or the eartip seal is poor),
then all samples will be noisy and accurate measurements will be impossible, in
which case the test result will indicate "noisy."
GebaEroscreenE_09a.doc 51 851 983/6 03/09