Distortion product otoacoustic emission suppression tuning curves in normal-hearing and hearing-impaired human ears

Abstract

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.

Growth of suppression in humans based on distortion-product otoacoustic emission measurements

“…4-8 are consistent with previous descriptions of DPOAE suppression in humans (Abdala, 1998(Abdala, , 2001Abdala et al, 1996;Abdala and Chatterjee, 2003;Abdala and Fitzgerald, 2003;Gorga et al, 2002aGorga et al, ,b, 2003Brown and Kemp, 1983;Kummer et al, 1995). Data from these studies showed the same dependence of growth of suppression on the relation between f 3 and f 2 .…”

“…These data are consistent with previous growth of suppression data based on auditory-nerve fiber responses in lower animals (e.g., Abbas and Sachs, 1976;Delgutte, 1990;Pang and Guinan, 1997) and are also consistent with measurements of suppression in basilar-membrane responses (e.g., Ruggero et al, 1992;Cooper and Rhode, 1996;Rhode and Cooper, 1993). Similar patterns have been observed in previous DPOAE suppression data as well (e.g., Abdala, 1998Abdala, , 2001Abdala and Fitzgerald, 2003;Abdala and Charterjee, 2003;Gorga et al, 2002Gorga et al, , 2003Kummer et al, 1995). Specifically, these previous studies showed that suppression grows most rapidly for suppressors lower in frequency than the signal frequency and that the growth of suppression decreases as suppressor frequency increases.…”

“…In most cases, stimulus levels below 40 dB sound pressure level (SPL) have not been explored. However, DPOAE suppression data at low stimulus levels are of interest, since evidence suggests that DPOAE estimates of cochlear gain are greatest for low-level stimuli (Gorga et al, 2003.…”

Low-frequency and high-frequency cochlear nonlinearity in humans

“…6 might be consistent with the reduced differences between tip and tail thresholds as observed in frequency-threshold curves of auditory neurons (see, for example, Sewell, 1984), although we do not, as yet, have data that can be used to more directly test this hypothesis in humans. Tip-to-tail differences estimated from DPOAE suppression tuning curves have been interpreted as estimates of cochlear-amplifier gain (e.g., Pienkowski and Kunov, 2001;Mills, 1998;Gorga et al, 2002Gorga et al, ,2003. If the interpretation of the data shown in Figs.…”

Tone-burst auditory brainstem response wave V latencies in normal-hearing and hearing-impaired ears

“…Recent work has demonstrated that differences in distortion-product otoacoustic emission (DPOAE) suppression tuning curves (STCs) between ears with normal hearing (NH) and ears with hearing loss (HL) depend on the stimulus level at which comparisons are made (Abdala and Fitzgerald, 2003;Gorga et al, 2003;Gruhlke et al, 2012). When compared at equal stimulus-probe levels (primary levels for f 1 and f 2 , the stimulus frequencies eliciting the DPOAE) relative to threshold (i.e., sensation level, SL), STCs in ears with mild-to-moderate HL were characterized by reduced gain (as estimated by tip-to-tail differences) and broader tuning (based on the quality factor, Q), compared to ears with NH.…”