Changes in auditory perception in the menstrual cycle

Case report: binaural beats music assessment experiment

We recruited subjects with the focus on people who were stressed and needed a break to experience relaxation. The study used inaudible binaural beats (BB) to measure the ability of BB to induce a relaxed state. We found through measuring brain wave activity that in fact BB seem to objectively induce a state of relaxation. We were able to see this across several scores, F3/F4 Alpha Assessment and CZ Theta Beta, calculated from EEG readings, that indicated an increase in positive outlook and a relaxing brain, respectively, and scalp topography maps. Most subjects also showed an improvement in Menlascan measurements of microcirculation or cardiovascular score, although the Menlascan scores and Big Five character assessment results were less conclusive. BB seem to have profound effects on the physiology of subjects and since the beats were not audible, these effects could not be attributed to the placebo effect. These results are encouraging in terms of developing musical products incorporating BB to affect human neural rhythms and corollary states of consciousness and warrant further research with more subjects and different frequencies of BB and different music tracks.

Sex differences in subcortical auditory processing only partially explain higher prevalence of language disorders in males

Males and females differ in their subcortical evoked responses to sound. For many evoked response measures, the sex difference is driven by a faster developmental decline of auditory processing in males. Using the frequency-following response (FFR), an evoked potential that reflects predominately midbrain processing of stimulus features, sex differences were identified in the response to the temporal envelope of speech. The pattern of later and smaller responses in males versus females is consistent with two of the three response features that track with language development and reading abilities. Therefore, here we analyzed subcortical response consistency, the third distinguishing feature of language ability. Furthermore, though the envelope is primarily a low-frequency response, the greatest sex differences were observed in harmonics encoding. To better understand these sex differences, we extended these findings to the temporal fine structure response, which is biased to high-frequency information. Using the same 516 participants as previously reported (Krizman et al., 2019), we analyzed the effect of sex across development on response consistency and the encoding of temporal fine structure, as indexed by the subtracted frequency-following response. We found that while males and females did not differ on response consistency, there was an effect of age on this measure. Moreover, while males still showed a faster decline in harmonic encoding, the magnitude and breadth of the sex differences were smaller (accounting for 2% variance) in the temporal fine structure response compared to the envelope response. These results suggest that sex differences are distinct, at least in part, from the differences that underlie language abilities and that developmental sex differences reflect subcortical auditory processing differences of both the temporal envelope and fine structure of sounds.

Role of sex hormones produced during menstrual cycle on brainstem encoding of speech stimulus

There are no studies attempted to determine the effects of different phases of menstrual cycle on frequency following response (FFR) for speech stimuli. The aim of the study was to determine the differences in latencies and amplitude of FFR waves recorded at four phases of menstrual cycle. In addition, it was also attempted to determine if there is any ear effect on latency and amplitude measures across the phases of menstrual cycle. FFR was recorded in 20 females in the age range of 18-25 years in the four menstrual cycles [Phase I-menses (day 1-3), Phase II-proliferative phase (day 11-14), Phase III-mid-luteal phase (day 17-22) and Phase IV-pre-menstrual phase (day 25-27)]. The results of the study showed that there was significant reduction in latencies and slight increase in amplitude during menses and mid-luteal phase compared to mid-cycle and pre-menstruation cycles. The present study supports the hypothesis that difference in the levels of sex hormones in women during menstrual cycle can affect brainstem encoding of speech stimuli.

Auditory beat stimulation and its effects on cognition and mood States

Auditory beat stimulation may be a promising new tool for the manipulation of cognitive processes and the modulation of mood states. Here, we aim to review the literature examining the most current applications of auditory beat stimulation and its targets. We give a brief overview of research on auditory steady-state responses and its relationship to auditory beat stimulation (ABS). We have summarized relevant studies investigating the neurophysiological changes related to ABS and how they impact upon the design of appropriate stimulation protocols. Focusing on binaural-beat stimulation, we then discuss the role of monaural- and binaural-beat frequencies in cognition and mood states, in addition to their efficacy in targeting disease symptoms. We aim to highlight important points concerning stimulation parameters and try to address why there are often contradictory findings with regard to the outcomes of ABS.

Sexual attractiveness of male chemicals and vocalizations in mice

Male-female interaction is important for finding a suitable mating partner and for ensuring reproductive success. Male sexual signals such as pheromones transmit information and social and sexual status to females, and exert powerful effects on the mate preference and reproductive biology of females. Likewise, male vocalizations are attractive to females and enhance reproductive function in many animals. Interestingly, females' preference for male pheromones and vocalizations is associated with their genetic background, to avoid inbreeding. Moreover, based on acoustic cues, olfactory signals have significant effects on mate choice in mice, suggesting mate choice involves multisensory integration. In this review, we synopsize the effects of both olfactory and auditory cues on female behavior and neuroendocrine functions. We also discuss how these male signals are integrated and processed in the brain to regulate behavior and reproductive function.

Estrogenic modulation of auditory processing: a vertebrate comparison

Sex-steroid hormones are well-known regulators of vocal motor behavior in several organisms. A large body of evidence now indicates that these same hormones modulate processing at multiple levels of the ascending auditory pathway. The goal of this review is to provide a comparative analysis of the role of estrogens in vertebrate auditory function. Four major conclusions can be drawn from the literature: First, estrogens may influence the development of the mammalian auditory system. Second, estrogenic signaling protects the mammalian auditory system from noise- and age-related damage. Third, estrogens optimize auditory processing during periods of reproductive readiness in multiple vertebrate lineages. Finally, brain-derived estrogens can act locally to enhance auditory response properties in at least one avian species. This comparative examination may lead to a better appreciation of the role of estrogens in the processing of natural vocalizations and mayprovide useful insights toward alleviating auditory dysfunctions emanating from hormonal imbalances.

Brainstem auditory evoked responses in different phases of menstrual cycle

BACKGROUND AND OBJECTIVES

Brainstem Auditory Evoked Potentials (BAEP) show variations with age, sex and other physiological factors. The gonadal steroids may also alter the neuronal functioning, but an electrophysiological evidence is sparse. This study was undertaken to analyze the auditory evoked response in females of the reproductive age group during four different hormonal states of the menstrual cycle.

METHODS

This was a prospective, single centered, longitudinal study. The waves of BAEP were recorded in 50 young females (of the ages of 19-36 years, who used no hormonal therapy) during four different phases of the same menstrual cycle. The peak latencies of the waves, I, II, III, IV and V, IPL I-III, I-V and III-V and the amplitude ratio, V/I were recorded and statistically analyzed.

RESULTS

A significant increase in the peak latencies of the waves, I-V in the oestrogen peak mid cycle was observed, while a significant decrease in the progesterone peak mid-luteal phase was observed. However, IPL did not show any statistically significant change in the above two phases. All the parameters did not show significant changes in the menstrual and the pre-menstrual phases.

INTERPRETATION AND CONCLUSION

The results indicated the BAEP changes in the mid follicular and the mid luteal phases of the menstrual cycle, thus suggesting the changes which were attributable to oestrogen and progesterone.

Estradiol treatment and hormonal fluctuations during the estrous cycle modulate the expression of estrogen receptors in the auditory system and the prepulse inhibition of acoustic startle response

Estrogens' effects on hearing are documented across species, but the responsible molecular mechanisms remain unknown. The presence of estrogen receptors (ER) throughout the auditory system offers a potential pathway of direct estrogenic effects on auditory function, but little is known about how each ER's expression is regulated by the overall hormonal status of the body. In the present study, we determined the effects of ovariectomy and chronic 17β-estradiol treatment on mRNA and protein expression of ERα and ERβ in peripheral (cochlea) and central (inferior colliculus) auditory structures of mice, as well as on auditory-related behavior using the acoustic startle response (ASR), prepulse inhibition (PPI), and habituation of the startle response. 17β-Estradiol treatment down-regulated ERα but not ERβ and increased PPI and latency of the ASR. Neither the magnitude nor the habituation of ASR was affected. Furthermore, ER's mRNA and protein expression in the inner ear were analyzed throughout the estrous cycle (proestrus, estrus, metestrus, and diestrus), revealing a negative correlation of circulating estrogens with ERα expression, whereas ERβ was stable. Our findings show that ER not only are present in both the peripheral and central auditory system but also that circulating estrogen levels down-regulate ERα expression in the auditory system and affect PPI and the latency of ASR, suggesting a key role of ERα as a hormone-induced modulator of the auditory system and behavior.

Expression patterns of estrogen receptors in the central auditory system change in prepubertal and aged mice

Estrogens are important in the development, maintenance and physiology of the CNS. Several studies have shown their effects on the processing of hearing in both males and females, and these effects, in part, are thought to result from regulation of the transcription of genes via their classical estrogen receptor (ER) pathway. In order to understand the spatiotemporal changes that occur with age, we have studied the expression of ERs in the central auditory pathway in prepubertal and aged CBA mice with immunohistochemistry. In prepubertal mice a clear dichotomy was noted between the expression of ERα and ERβ. ERβ-positive neurons were found in the metencephalon whereas the majority of ERα was found in mesencephalon, diencephalon or the telencephalon. In the aged animals a different pattern of ER expression was found in terms of location and overall intensity. These age-induced changes in the expression pattern were generally not uniform, suggesting that region-specific mechanisms regulate the ERs' age-related expression. Neither the prepubertal nor the aged animals showed sex differences in any auditory structure. Our results demonstrate different age-dependent spatial and temporal changes in the pattern of expression of ERα and ERβ, suggesting that each ER type may be involved in distinct roles across the central auditory pathway in different periods of maturation.

Estradiol protects the cochlea against gentamicin ototoxicity through inhibition of the JNK pathway

Gentamicin induces outer hair cell death through the apoptotic pathway. It has been reported that this death pathway of outer hair cells is mediated by specific apoptotic enzymes including c-jun N-terminal kinase (JNK) and caspases. 17beta-Estradiol (E2), the most potent estrogen, is known to function as an antiapoptotic agent to prevent the death of various cell types. The purpose of the present study was to examine the effects of E2 on gentamicin-induced apoptotic cell death in outer hair cells. The basal turn organ of Corti explants from p3 or p4 rats were maintained in a tissue culture and exposed to 100muM gentamicin for 48h. The effects of E2 on gentamicin-induced outer hair cell loss, JNK activation, and staining for terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick-end labeling (TUNEL) were examined. E2 significantly decreased gentamicin-induced outer hair cell loss in a dose-dependent manner. JNK activation and TUNEL staining were observed in organ of Corti explants exposed to gentamicin, and staining levels were significantly decreased by E2 treatment. The results indicate that, through the inhibition of JNK and subsequent apoptotic reactions, E2 decreases outer hair cell loss induced by gentamicin ototoxicity.

Estrogen receptors in the central auditory system of male and female mice

The estrogen receptors in the central auditory system of male and female mice were characterized using immunocytochemical methods. Estrogen receptors alpha and beta (ERalpha, ERbeta) were localized predominantly in the ventral cochlear nucleus, nucleus of the trapezoid body, the lateral- and medio-ventral periolivary nuclei, the dorsal lateral lemniscus, and the inferior colliculus. The medial geniculate nucleus was negative for both ERalpha and ERbeta whereas the auditory cortex was positive for ERalpha. The lateral superior olive, the ventral lateral lemniscus and the central nucleus of the inferior colliculus expressed only ERbeta. The differential localization of ERalpha and ERbeta may indicate distinct roles for these two receptors in auditory processing. No major differences in the pattern, number or intensity of receptor expression was found between male and female animals. The comprehensive anatomic map that is constructed for ERalpha and ERbeta in the central auditory pathway will be a useful foundation to elucidate the complexity of estrogen actions in the auditory system.

Estrogen receptor beta protects against acoustic trauma in mice

The hormone estradiol affects the auditory system both by itself and by its interaction with neuroprotective factors. In this study, we examined the role of estrogen receptors (ERs) in response to auditory trauma. We found a ligand-dependent protective role for ERbeta in the auditory system by investigating mice deficient in ERalpha (ERKO mice), ERbeta (BERKO mice), and aromatase (ARKO mice). Basal auditory brainstem response (ABR) thresholds were similar in all animals. An acoustic trauma causing a temporary hearing loss raised ABR thresholds in male and female BERKO and ARKO mice compared with WT and ERKO mice. The ERalpha-selective agonist, propyl(1H) pyrazole-1,3,5-triyl-trisphenol (PPT), partially protected ARKO mice from trauma, while the ERbeta-selective agonist, 2,3-bis (4-hydroxyphenyl)-propionitrile (DPN), protected WT and ARKO mice. Immunohistochemistry and western blotting confirmed the expression of ERbeta in cochlea of WT males and females. Levels of brain-derived neurotrophic factor (BDNF), a neuroprotective peptide that can be induced by estrogen, was lower in BERKO and ARKO mice compared with WT. DPN treatment increased BDNF expression in ARKO mice. These data indicate ERbeta-mediated neuroprotection involving BDNF in the auditory system of males and females.

Gender-specific sensitivity to low frequencies in male speech

The perception of human voices as naturally occurring sound objects may correspond to the detection of specific components of the frequency spectrum. In the current study, a psychophysical experiment was undertaken to investigate whether male and female listeners differed with respect to which frequencies were important in the perception of a male voice as a natural sound object. For females (but not males) the presence of low frequencies (<220 Hz), but not high frequencies (>4 kHz), was most crucial in the perception of a male voice as natural. This finding could be compatible with a neuroethological interpretation: low frequencies in the range that were studied are important in distinguishing male from female voices and mature from immature male voices.

Seasonal changes in frequency tuning and temporal processing in single neurons in the frog auditory midbrain

Frogs rely on acoustic signaling to detect, discriminate, and localize mates. In the temperate zone, reproduction occurs in the spring, when frogs emerge from hibernation and engage in acoustically guided behaviors. In response to the species mating call, males typically show evoked vocal responses or other territorial behaviors, and females show phonotactic responses. Because of their strong seasonal behavior, it is possible that the frog auditory system also displays seasonal variation, as evidenced in their vocal control system. This hypothesis was tested in male Northern leopard frogs by evaluating the response characteristics of single neurons in the torus semicircularis (TS; a homolog of the inferior colliculus) to a synthetic mating call at different times of the year. We found that TS neurons displayed a seasonal change in frequency tuning and temporal properties. Frequency tuning shifted from a predominance of TS units sensitive to intermediate frequencies (700-1200 Hz) in the winter, to low frequencies (100-600 Hz) in the summer. In winter and early spring, most TS neurons showed poor, or weak, time locking to the envelope of the amplitude-modulated synthetic call, whereas in late spring and early summer the majority of TS neurons showed robust time-locked responses. These seasonal differences indicate that neural coding by auditory midbrain neurons in the Northern leopard frog is subject to seasonal fluctuation.

Steroid-Dependent Auditory Plasticity Leads to Adaptive Coupling of Sender and Receiver

For seasonally breeding vertebrates, reproductive cycling is often coupled with changes in vocalizations that function in courtship and territoriality. Less is known about changes in auditory sensitivity to those vocalizations. Here, we show that nonreproductive female midshipman fish treated with either testosterone or 17beta-estradiol exhibit an increase in the degree of temporal encoding of the frequency content of male vocalizations by the inner ear that mimics the reproductive female's auditory phenotype. This sensory plasticity provides an adaptable mechanism that enhances coupling between sender and receiver in vocal communication.

Auditory brain stem response throughout the menstrual cycle

A prospective study was performed to evaluate the changes in the auditory brain stem response (ABR) that occur in healthy premenopausal women throughout the menstrual cycle. Ninety-four women with ovulatory menstrual cycles underwent ABR testing by auditory evoked potentials for wave I, III, and V latencies and for interpeak I-III, I-V, and III-V intervals during the follicular, periovular, and luteal phases of the menstrual cycle. The wave latencies and the interpeak intervals showed shorter values during the periovular phase than during the luteal phase (p < .05) and shorter values during the follicular phase for wave I (p < .05) and interpeak interval I-V (p < .05). The ABR seems to be influenced by the variations of ovarian steroids that occur during the menstrual cycle.

Effects of patch or gel estrogen therapies on auditory brainstem response in surgically postmenopausal women: a prospective, randomized study

OBJECTIVE

To study the effects of gonadal steroids on the nongenital audiological target in surgically postmenopausal women treated with patch or gel transdermal estrogen therapy (ET).

DESIGN

Prospective randomized study.

SETTING

Research Group for Sexology, University of Catania, Italy.

PATIENT(S)

One hundred twenty-two surgically postmenopausal women.

INTERVENTION(S)

Transdermal E(2) by patch or gel, and evaluation of auditory brainstem response by auditory-evoked potentials for waves I, III, and V latencies, and for interpeak I-III, I-V, and III-V intervals.

MAIN OUTCOME MEASURE(S)

Changes in auditory wave latencies and in interpeak intervals during treatment with ET with respect to baseline levels.

RESULT(S)

One hundred two women completed the study. Forty-eight subjects used E(2) patches and 54 E(2) gel. No significant difference was observed in plasma E(2) improvement and in auditory brainstem response values with the two estrogen (E) formulations. The wave latencies and the interpeak intervals showed lower values during the E treatment than at baseline.

CONCLUSION(S)

Auditory brainstem response seems to depend on the type of E given. Our data suggest that fluctuating E levels act on waves, even if the exact mechanism of the gonadal steroids is not clear. However, we believe that E could influence neuronal plasticity, the metabolic levels of neurotransmitters, and thus, the neuronal conduction time into the audiological system.

Seasonal plasticity of peripheral auditory frequency sensitivity

Female midshipman fish (Porichthys notatus) use the auditory sense to detect and locate vocalizing males during the breeding season. Detection of conspecific vocal signals is essential to their reproductive success and can evoke strong phonotactic responses in gravid females but not in spent females that have released all of their eggs. Here, we test the hypothesis that seasonal variation in reproductive state affects the neurophysiological response properties of the peripheral auditory system in female midshipman fish. Iso-intensity responses of eighth nerve afferents from the sacculus, the main auditory end organ of the inner ear, to individual tones were measured for spike rate and vector strength (VS) of synchronization. Most auditory saccular units in reproductive, summer females showed robust temporal encoding up to 340 Hz, whereas nonreproductive winter females showed comparable encoding only up to 100 Hz. The dramatic upward shift in temporal encoding among summer fish was paralleled by increases in best frequency (BF), maximum evoked spike rate at BF, VS values at BF, and the percentage of units that showed significant VS to iso-intensity tones >140 Hz. Reproductive summer females were best suited to encode the higher harmonic components of male advertisement calls. This first demonstration of a natural cyclicity in peripheral auditory frequency sensitivity among vertebrates may represent, in this case, an adaptive plasticity of the female midshipman's auditory system to enhance the acquisition of auditory information needed for mate identification and localization during the breeding season.

Auditory brainstem response in premenopausal women taking oral contraceptives

BACKGROUND

The aim of this prospective study was to evaluate the effects of the new monophasic oral contraceptives on the audiological system in premenopausal women.

METHODS

The auditory brainstem response (ABR) was measured in 94 women during the follicular, periovular and luteal phases of one menstrual cycle in which ovulation was confirmed using sonography and serum progesterone concentration. The latencies for waves I, III and V were determined, and the inter-peak intervals were calculated for waves I-III, I-V and III-V. All 94 women began taking oral contraceptives: 23 women used 20 microg ethinyl estradiol (EE) plus 150 microg desogestrel, 24 women used 30 microg EE plus 75 microg gestodene, and 47 women used 15 microg EE plus 60 microg gestodene. During the third month of contraceptive intake, each subject was again tested for ABR, as above.

RESULTS

The wave latencies and inter-peak intervals showed shorter values during the periovular phase with respect to the luteal phase (P < 0.05), the follicular phase for wave I and for inter-peak interval I-V (P < 0.05) of the menstrual cycle. All of the ABR results in pill users were statistically different from those of the periovular phase (P < 0.05), though similar to those of both the luteal and follicular phases (P = NS).

CONCLUSIONS

ABR seems to depend on the variations of ovarian steroids during the menstrual cycle and during oral contraceptive intake.

Neural mechanisms and behaviors for acoustic communication in teleost fish

Sound communication is not unique to humans but rather is a trait shared with most non-mammalian vertebrates. A practical way to address questions of vocal signal encoding has been to identify mechanisms in non-mammalian model systems that use acoustic communication signals in their social behavior. Teleost fishes, the largest group of living vertebrates, include both vocal and non-vocal species that exploit a wide range of acoustic niches. Here, we focus on those vocal species where combined behavioral and neurobiological studies have recently begun to elucidate a suite of adaptations for both the production and the perception of acoustic signals essential to their reproductive success and survival. Studies of these model systems show that teleost fish have the vocal-acoustic behaviors and neural systems both necessary and sufficient to solve acoustic problems common to all vertebrates. In particular, behavioral studies demonstrate that temporal features within a call, including pulse duration, rate and number, can all be important to a call's communicative value. Neurobiological studies have begun to show how these features are produced by a vocal motor system extending from forebrain to hindbrain levels and are encoded by peripheral and central auditory neurons. The abundance and variety of vocal fish present unique opportunities for parallel investigations of neural encoding, perception, and communication across a diversity of natural, acoustic habitats. As such, investigations in teleosts contribute to our delineating the evolution of the vocal and auditory systems of both non-mammalian and mammalian species, including humans.

Long-term repeatability of the pure-tone hearing threshold and its relation to noise exposure

Audiometric repeatability is examined for a population of 356 male and female industrial employees (712 ears), sub-divided according to the amount of previous noise exposure. Re-tests were carried out after an interval averaging 13 months. After a similar interval, 150 of the subjects gave a third audiogram. Fixed-frequency self-recording audiometry was employed, using common equipment and procedures throughout. Results are presented as distributions of the algebraic test-re-test differences for each frequency and for the frequency combination 1-2-3 kHz. Repeatability was best at 1 and 2 kHz and substantially poorer at 6 kHz. Cumulative distributions of the signless differences show that more than 50% of initial hearing threshold levels repeated to better than 5 dB. For all frequencies except 6 kHz the mean values of signless test-re-test differences for the various sub-groups were between 3.4 and 5.6 dB; at 6 kHz the values were between 5.8 and 7.8 dB. In the case of the three-frequency average, the mean differences were reduced to between 2.8 and 3.8 dB. A few repeats (about one in 200) stand out as clearly anomalous; these occur only in isolation and mainly at the higher frequencies. The performance of groups classified by the amount of their previous noise exposure did not differ significantly. In the case of those tested three times, the repeatability over the second inter-test interval showed at most a marginal improvement compared with the first interval.

Auditory sensitivity and tone-sequence reproduction in oral contraceptive users and nonusers

In two stages spanning a single academic year, 10 women using oral contraceptives and 11 not using oral contraceptives were tested on their auditory threshold sensitivity to six frequencies (250, 750, 1500, 3000, 6000, and 8000 Hz) as a function of phases of the menstrual cycle. 11 women (5 users and 6 nonusers) were also tested on their ability to reproduce successively longer tone sequences. Results showed that there was little variation due to phase of the menstrual cycle, with the exception that oral contraceptive users showed lower relative thresholds at low frequencies during the postmenstrual phase. Over-all, oral contraceptive users had higher absolute and relative thresholds than nonusers, except at 3000 Hz. Although not statistically significant, results on the tone-reproduction test showed an enhanced ability to reproduce tones during the premenstrual phase for women using oral contraceptives. Results are discussed in relation to previous findings.

Influence of menopause on the auditory brainstem response

Auditory brainstem response (ABR) wave latency, interpeak interval and amplitude as a function of intensity were measured in 40 subjects divided into equal groups of postmenopausal females, age-matched males and young adults of both sexes. The results illustrate that age and gender play a significant role in ABR wave latency and amplitude. A larger age effect occurred for the female subjects. While this does not dispute an anatomical explanation for the gender effect in ABR, hormonal changes accompanying menopause may also account for some of the gender differences noted in ABR.

Effect of the menstrual cycle on the auditory brainstem response

The present study sought to determine if the gender difference in auditory brainstem (ABR) latency and peak amplitude varies systematically across the menstrual cycle. Behavioral thresholds and auditory-evoked brainstem responses to alternating click stimuli were obtained from 17 normal hearing young adults (10 female, 7 male). Absolute behavioral thresholds and ABR measurements were compared every other day over a complete menstrual cycle. Results show consistent gender differences in ABR latency, peak amplitude, and behavioral threshold of the ABR stimuli, but these differences do not vary across the menstrual cycle.

Effects of the ovarian and contraceptive cycles on absolute thresholds, auditory fatigue and recovery from temporary threshold shifts at 4 and 6 kHz

Absolute thresholds at 4 and 6 kHz were tested in three sessions before and after 20 min of exposure to 105 dB(A) pink noise in 12 young normal-cycling females, 11 young females on oral contraceptives and 8 young men. Women on contraceptives showed lower resting thresholds, larger temporary threshold shift (TTS) and higher recovery rates than normal-cycling females. The analysis of resting thresholds, auditory fatigue and recovery from auditory fatigue did not evidence any sex-linked difference. Significant differences linked to the phases of the menstrual cycle and of the contraceptive cycle were observed during recovery from auditory fatigue at 4 kHz and in resting thresholds at 6 kHz. Application of Kendall's coefficient of concordance confirmed these results. Absolute thresholds were highest at menstruation and lowest in the postovulatory phase in normal-cycling females and in women on oral contraceptives, during the days of pill ingestion. Oral contraception is probably a more important factor of change in hearing performance than the phases of the menstrual cycle.