It has been proposed that the clinical accuracy of distortion product otoacoustic emissions (DPOAEs) is affected by the interaction of distortion and reflection sources contributing to the response. This study evaluated changes in dichotomous-decision test performance and threshold-prediction accuracy when DPOAE source contribution was controlled. Data were obtained from 205 normal and impaired ears with L 2 ranging from 0 to 80 dB SPL and f 2 = 2 and 4 kHz. Data were collected for control conditions (no suppressor, f 3 ) and with f 3 presented at 3 levels that previously had been shown to reduce the reflection-source contribution. The results indicated that controlling source contribution with a suppressor did not improve diagnostic accuracy (as reflected by ROC curve area) and frequently resulted in poorer test performance compared to control conditions. Likewise, correlations between DPOAE and behavioral thresholds were not strengthened when using the suppressors to control source contribution. While improvements in test accuracy were observed for a subset of subjects (normal ears with the smallest DPOAEs and impaired ears with the largest DPOAEs), the lack of improvement for the larger, unselected subject group suggests that DPOAEs should be recorded in the clinic without attempting to control the source contribution with a suppressor.

Distortion-product otoacoustic emission ͑DPOAE͒ input/output ͑I/O͒ functions were measured in 322 ears of 176 subjects at as many as 8 f 2 frequencies per ear for a total of 1779 I/O functions. The f 2 frequencies ranged from 0.7 to 8 kHz in half-octave steps. Behavioral thresholds ͑BTs͒ at the f 2 frequencies ranged from Ϫ5 to 60 dB hearing loss ͑HL͒. Both linear-pressure and nonlinear, two-slope functions were fitted to the data. The two-slope function describes I/O compression as output-controlled self-suppression. Most I/O functions ͑96%͒ were better fitted by the two-slope method. DPOAE thresholds based on each method were used to predict BTs. Compared to estimates based on linear-pressure functions, individual BTs predicted from DPOAE thresholds based on the two-slope model had lower residual error and accounted for more variance. Another advantage of the two-slope method is that it provides an estimate of response growth rate ͑RGR͒ that is not tied to threshold. At all frequencies, the median low-level RGR ͑across I/O functions of the same f 2 and BT͒ usually increased as BT increased, while high-level compression decreased. The observed characteristics of DPOAE I/O functions are consistent with the loss of cochlear compression that is typically associated with mild-to-moderate HL.

Distortion product otoacoustic emission (DPOAE) suppression measurements were made in 20 subjects with normal hearing and 21 subjects with mild-to-moderate hearing loss. The probe consisted of two primary tones (f2, f1), with f2 held constant at 4 kHz and f2/f1 = 1.22. Primary levels (L1, L2) were set according to the equation L1 = 0.4 L2 + 39 dB [Kummer et al., J. Acoust. Soc. Am. 103, 3431-3444 (1998)], with L2 ranging from 20 to 70 dB SPL (normal-hearing subjects) and 50-70 dB SPL (subjects with hearing loss). Responses elicited by the probe were suppressed by a third tone (f3), varying in frequency from 1 octave below to 1/2 octave above f2. Suppressor level (L3) varied from 5 to 85 dB SPL. Responses in the presence of the suppressor were subtracted from the unsuppressed condition in order to convert the data into decrements (amount of suppression). The slopes of the decrement versus L3 functions were less steep for lower frequency suppressors and more steep for higher frequency suppressors in impaired ears. Suppression tuning curves, constructed by selecting the L3 that resulted in 3 dB of suppression as a function of f3, resulted in tuning curves that were similar in appearance for normal and impaired ears. Although variable, Q10 and Q(ERB) were slightly larger in impaired ears regardless of whether the comparisons were made at equivalent SPL or equivalent sensation levels (SL). Larger tip-to-tail differences were observed in ears with normal hearing when compared at either the same SPL or the same SL, with a much larger effect at similar SL. These results are consistent with the view that subjects with normal hearing and mild-to-moderate hearing loss have similar tuning around a frequency for which the hearing loss exists, but reduced cochlear-amplifier gain.

Previously described multivariate analyses were robust in that they improved test performance when applied to an entirely new set of DPOAE data. This, in turn, suggests that the previously described multivariate solutions may have clinical utility in that they are expected to improve test performance at no additional cost in terms of data-acquisition or data-analysis time. In addition to demonstrating that these solutions generalized to new data, an alternative approach to interpreting multifrequency DPOAE measurements is provided that includes the advantages of using multivariate analyses. This new metric may be useful when DPOAEs are used for screening purposes.

Objective-To determine the maximum stimulus levels at which a measured auditory steady-state response (ASSR) can be assumed to be a reliable measure of auditory thresholds.Design-ASSR thresholds were measured at octave frequencies from 500 to 4000 Hz in 10 subjects with profound hearing loss. These subjects provided no behavioral responses to sound at the limits of pure-tone audiometers and at the limits of the stimulus levels produced by the ASSR device. Subjects were divided into two groups of five, with repeated measures obtained within the same session in one group and repeated measures obtained in a separate session on a different day in the other group.Results-ASSR thresholds were observed in all 10 subjects at each of four frequencies and in both trials. On average, these ASSR thresholds were observed at 100 dB HL (SD = 5 dB). Because these responses were at least 18 to 22 dB below the limits of the equipment where all subjects had no behavioral responses, it is reasonable to conclude that the ASSRs were not generated by the auditory system.Conclusions-An artifact or distortion may be present in the recording of ASSRs at high levels. These data bring into question the view that there is a wider dynamic range for ASSR measurements compared with auditory brain stem response measurements, at least with current implementation.With the advent of universal newborn hearing screening (UNHS), clinicians are being asked to provide diagnostic audiological evaluations on infants within the first few weeks or months of life. This seems reasonable, since it is widely thought that the success of intervention will depend, at least in part, on the age at which intervention begins (Moeller, 2000; YoshinagaItano et al., 1998). Thus, if UNHS identifies newborn infants with hearing loss, it will be important to initiate intervention as soon as possible after the identification. At these ages, however, it is not clinically feasible to rely on behavioral responses to sound to provide an estimate of the magnitude and configuration of hearing loss. Clinicians must rely on measurements that do not require a voluntary response on the part of the infant if intervention is to be initiated soon after identification.The auditory brainstem response (ABR) is considered an objective electrophysiological measure and has been used to provide information about auditory sensitivity in patients who are either too young or who are functioning at a developmental level at which reliable behavioral response measurements are not possible. These responses are elicited by stimuli with rapid onsets. Such stimuli are characterized by a spread of energy, the extent of which depends on how these stimuli are generated. Several stimulus paradigms have been combined with ABR measurements to obtain frequency-specific responses. These methods include the derived-band technique (Don, Eggermont and Brackman, 1979), the notched-noise technique (Picton et al., 1979;Stapells, Gravel and Martin, 1995), and the use of tone bursts in quiet (Gorga et al., 1988...