Interacoustics OtoRead Instructions For Use Manual page 63

OtoRead™ Instructions for Use - US Page 57
Pass/Refer criteria for TEOAE
The same basic principles that underlie DPOAE Pass/Fail criteria can be applied to 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 %.
Please note: The SNR limits for transients are lower than the corresponding limits for distortion products
TM
primarily because the traditional noise calculation used in TEOAE measurements (and in the OtoRead
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 OtoRead uses a novel noise-rejection algorithm (patent pending) that permits accurate DPOAE
and TEOAE measurements in background noise and babble as high as 55 dB SPL to 65 dB SPL (A-
TM
weighted). Briefly explained, use of available memory in the OtoRead 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 ear tip seal is poor), then all samples will be noisy and accurate
measurements will be impossible. In such cases, the test result will indicate 'noisy'.