Full-term and preterm infants were evaluated with click+voked and distortionproduct otoacoustic emissions [CEOEs and DPOEs]. The CEOEs and D W E s recorded from each individual ear were analyzed by calculating the rootimean-square levels within halfa%ave bands. The fail criterion of the OE tests was that the halfoctave RMS DPOE or CEOE levels of an ear under test were below the 1 0 t h percentile of full-term newborns in t w o o r more bands. The DPOE data were collected from 118 ears of 61 premature babies; 80 (68%] ears passed the DPOE test, 30 [25%] ears without middle ear effusions failed the test, and 8 (7%] ears with effusions also failed. The CEOE data were collected from 128 ears of 65 premature babies; 102 (80%) ears passed the CEOE test, 18 (14%) ears without middle ear effusions failed the test, and 8 (6%] ears with effusions also failed. In 23 of 80 ears (29%) that passed the D W E test and in 23 of 102 ears (23%] that passed the CEOE test, RMS OE levels of preterm infants were above the 9 0 t h percentile of fulLterm newborns. The analyses of the combined DPOE and CEOE data obtained from a group of 25 ears of full-term newborns and from a group of 72 ears of preterm babies showed statistically significant correlations between the DPOE and CEOE rootmean-square levels in each of the half-octave bands in the 1.4 to 4 kHz region. For 42 preterm infants tested with auditory brain stem response [ABR), specificity was 86% for CEOE and 74% for DPOE. All infants who failed the ABR also failed OE tests. To the best of our knowledge, this study is the first using combined D W E s , CEOEs, and ABRs for preterm babies. It showed the feasibility of D W E s and CEOEs for this population.

The performance of distortion product otoacoustic emissions (DPOEs) as a frequency-specific test of sensorineural hearing loss was evaluated in 142 ears of human adults with normal middle-ear function. The DPOE was measured with the stimulus levels of the two tones equal to 65 dB SPL (re 20 mu Pa) and the ratio between the two frequencies 1.2. In the DPOE test, the cochlear function of an ear at a test frequency was predicted to be normal or abnormal depending upon whether the DPOE level with the geometric mean of the two stimulus frequencies at the test frequency was greater or less than a criterion. The DPOE test outcomes were evaluated against the pure-tone hearing threshold as the standard. We found the sensitivity, specificity and predictive efficiency of the test to be 85-89% at 6000 and 4000 Hz, 82-83% at 2000 Hz and 78-79% at 1000 Hz, respectively. The performance was also evaluated using decision theory in terms of the area under the receiver operating characteristics. The latter was found to range from 0.90 (for 1000 Hz) to 0.94 (for 6000 Hz). These findings support the conclusion that the DPOEs can form a useful frequency-specific objective test of cochlear function.

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Although distortion-product otoacoustic emissions (DPOEs) have been studied in adults recently, there is little information regarding them in young children. DPOEs and click-evoked otoacoustic emissions (CEOEs) were measured from a same group of normal and hearing-impaired children (age 4 through 10 years) and normal adults (age 22 through 29 years). Measurements of DPOEs in 13 children's ears with normal hearing showed higher levels of emissions in the 700- to 1400-Hz and 5.7-kHz regions relative to the data obtained in 10 normal adult ears. The 22 ears of children with sensorineural hearing loss demonstrated agreement between pure-tone audiograms and "DPOE audiograms." Measurements of CEOEs revealed that the average level of emission in 15 normal-hearing children's ears was slightly lower than that previously obtained in newborns, but slightly higher than that of adults. In children, the CEOE spectral components in the 4- to 6-kHz region were lower than in newborns, but higher than in adults. These results support the view that the DPOEs and CEOEs comprise a valuable tool in assessment of cochlear function in subjects of all ages.