Relationship between distortion product otoacoustic emissions and pure tone thresholds in normal and hearing-impaired ears

To establish clinical criteria for distortion product otoacoustic emissions (DPOAEs) in order to distinguish normal-hearing from hearing-impaired ears, DPOAEs were measured and evaluated in 325 normal and 291 cochlear-impaired human ears using an ILO92 Otoacoustic Emission Analyzer. The background noise level was too variational in each individual ear to ignore in DPOAE measurements. Therefore, the value of the difference between the DPOAE amplitude and the background noise level (DPOAE noise) was calculated and compared with the pure tone threshold at 1 kHz, 2 kHz and 4 kHz. It was difficult, however, to precisely separate normal-hearing and hearing impaired ears with DPOAE noise values because many normal ears presented small amplitudes of DPOAEs and some impaired ears showed high amplitudes. Therefore, cumulative distributions of sensitivity (normal hearing ears identified as normal hearing) and specificity (hearing impaired ears identified as hearing impaired) were constructed and used to calculate a cut off point for DPOAE-noise in order to separate normal hearing from hearing impaired ears. It is considered that the cut-off points (DPOAE noise values of 7.3 dB at 1 kHz, 10.3 dB at 2 kHz and 16.1 dB at 4 kHz) at which the false alarm rates (1 specificity: the rate of hearing impaired ears incorrectly identified as normal hearing) correspond to 5% can be useful for clinical evaluation of DPOAEs.