PREDICTING PURE-TONE THRESHOLDS IN NORMAL AND HEARING-IMPAIRED EARS WITH DISTORTION-PRODUCT EMISSION AND AGE

Distortion product emission (DPE) growth functions, demographic data, and pure tone thresholds were recorded in 229 normal-hearing and heari ng-impaired ears. Half of the data set (115 ears) was used by a discri minant analysis routine to classify DPE and demographic features into either a normal pure tone threshold (PTT) group or an impaired PTT gro up (PTT greater than 30 dB SPL) at six frequencies in the audiometric range. The six discriminant functions developed from this classificati on process were then used to predict pure tone threshold group members hip in the remaining 114-ear data set. Frequency-specific prediction a ccuracy varied from 71% (correct classification of hearing impairment at 1025 Hz) to 92% (correct classification of normal hearing at 2050 H z). Of the 45 DPE and demographic variables evaluated, the DPE amplitu de associated with an f2 of moderate level (50 dB SPL) and a frequency corresponding to pure tone threshold was generally most predictive. D PE level was found to be weakly correlated with subject age and perhap s for this reason age was frequently included in discriminant function s. For our data, discriminant functions with one variable, two variabl es, or 5-10 variables showed no differences in predictive performance. This research suggests that DPE measures can reliably categorize pure tone thresholds as normal or impaired in large populations with varie d cochlear hearing status.