Sensitivity to interaural time differences at high frequencies is demonstrated in a number of experiments. Two types of waveforms are used—bands of noise and two-tone complexes. Variables studied are rate and depth of fluctuation of the envelope, overall intensity, and additivity of interaural time information across frequency regions. In many conditions of listening, sensitivity to interaural time differences at high frequencies compares favorably with sensitivity at low frequencies—good performace requires only tens of microseconds of interaural time delay. Subject Classification: [43]65.62, [43]65.68.

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Click-evoked otoacoustic emissions (CEOAEs) are echo-like waveforms emitted by normal-hearing cochleas in response to a brief transient. CEOAEs are known to be stronger in females than in males. In this experiment, the CEOAEs of homosexual and bisexual females were found to be intermediate to those of heterosexual females and heterosexual males. A parsimonious explanation is that the auditory systems of homosexual and bisexual females, and the brain structures responsible for their sexual orientation, have been partially masculinized by exposure to high levels of androgens prenatally. No difference in CEOAEs was observed between homosexual and heterosexual males.Evidence continues to accumulate about the biological concomitants of human homosexuality. To date, homosexual males have been reported to have larger suprachiasmatic nuclei of the hypothalamus (1), smaller interstitial nuclei of the anterior hypothalamus (2), larger anterior commissures (3), and thicker isthmuses of the corpus callosum (4) than heterosexual males. (Which, if any, of these concomitants is actually a substrate for homosexual behavior-as distinguished from a structure that simply covaries with homosexual behavior and its structural substrates-is yet to be determined.) Supplementing the findings about differences in brain structure are findings about the heritability of homosexuality. Studies of twins suggest heritability values of about 0.4-0.7 for homosexuality in both males and females (5, 6), and there is evidence for a linkage between certain markers on the X chromosome and sexual orientation in males but not in females (7,8).With the exception of the heritability study on twins (6), all of the current evidence for biological concomitants of homosexuality is for males only. Here, we report that the peripheral auditory systems of homosexual females differ from those of heterosexual females, and the nature of the difference is consistent with the idea that homosexual females are exposed to higher levels of androgens prenatally than are heterosexual females.Otoacoustic emissions (OAEs) are weak sounds produced by elements in the inner ear (refs. 9 and 10; for a review, see ref. 11). These sounds can be measured using a miniature microphone attached to a probe tip inserted into the external ear canal. There are several types of OAE, but only two will be considered in this paper. Click-evoked otoacoustic emissions (CEOAEs) are echo-like waveforms that are emitted in response to a brief transient sound. A click of about one-tenth of a millisecond in duration can produce a CEOAE lasting tens of milliseconds in any person having a normal cochlea and middle-ear system. Because CEOAE waveforms are weak, the responses to many clicks must be averaged for a CEOAE waveform to be obtained. CEOAE waveforms differ considerably across ears, but seem to be stable within an ear (12, 13).Spontaneous otoacoustic emissions (SOAEs) are tonal or narrow-band sounds that are continuously emitted by an ear in the absence of eliciting acoustic stimulation....

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In this study, a nonlinear version of the stimulus-frequency OAE (SFOAE), called the nSFOAE, was used to measure cochlear responses from human subjects while they simultaneously performed behavioral tasks requiring, or not requiring, selective auditory attention. Appended to each stimulus presentation, and included in the calculation of each nSFOAE response, was a 30-ms silent period that was used to estimate the level of the inherent physiological noise in the ear canals of our subjects during each behavioral condition. Physiological-noise magnitudes were higher (noisier) for all subjects in the inattention task, and lower (quieter) in the selective auditory-attention tasks. These noise measures initially were made at the frequency of our nSFOAE probe tone (4.0 kHz), but the same attention effects also were observed across a wide range of frequencies. We attribute the observed differences in physiological-noise magnitudes between the inattention and attention conditions to different levels of efferent activation associated with the differing attentional demands of the behavioral tasks. One hypothesis is that when the attentional demand is relatively great, efferent activation is relatively high, and a decrease in the gain of the cochlear amplifier leads to lower-amplitude cochlear activity, and thus a smaller measure of noise from the ear.

Click-evoked otoacoustic emissions (CEOAEs) were previously shown to be significantly less strong in homosexual and bisexual females than in heterosexual females. Here it is reported that the spontaneous otoacoustic emissions (SOAEs) of those same 60 homosexual and bisexual females were less numerous and weaker than those in 57 heterosexual females. That is, the SOAEs of the homosexual and bisexual females were intermediate to those of heterosexual females and heterosexual males. The SOAE and CEOAE data both suggest that the cochleas of homosexual and bisexual females have been partially masculinized, possibly as part of some prenatal processes that also masculinized whatever brain structures are responsible for sexual orientation. For males of all sexual orientation, the SOAEs were less numerous and weaker than for the females, and there were no significant differences among the 56 heterosexual, 51 homosexual, and 11 bisexual males. All subjects passed a hearing screening test. When all SOAEs above 3000 Hz were excluded (as a control against incipient, undetected hearing loss) the same results were obtained as with the full range of data (550-9000 Hz). The differential use of oral contraceptives by the heterosexual and nonheterosexual females also could not explain the differences in their OAEs.

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Otoacoustic emissions (OAEs) of two types--spontaneous and evoked distortion products--were studied before, during, and following a period of aspirin use. As previously reported, aspirin consumption uniformly reduced the spontaneous OAEs (SOAEs) to unmeasurable or extremely low levels. Aspirin consumption also reduced the amplitude of the evoked distortion products (EDPs) but did not eliminate them entirely. The amplitude of the EDP and its change with aspirin consumption were related to both the proximity of the EDP to the frequency of the SOAE and to the level of the primaries producing the EDP. At low primary levels, even with the SOAE absent (due to aspirin consumption, or suppression), EDPs near the SOAE frequency were 10-20 dB higher than when they were 100 Hz away from the SOAE frequency.