Low-frequency Tones Research Articles

Rats exhibit asymmetrical retention functions for hedonic and nonhedonic samples in many-to-one symbolic delayed matching to sample

Rats were initially trained in a symbolic delayed matching-to-sample task either to discriminate hedonic samples that consisted of food or no food or to discriminate tone samples that differed in frequency and location. The retention functions for both the hedonic and tone samples were asymmetric, with forgetting of the food sample or the high-frequency tone occurring more rapidly than forgetting of the no-food sample or the low-frequency tone. Next, many-to-one (MTO) training was given in which tone samples were added for the rats initially trained with hedonic samples, and hedonic samples were added for the rats initially trained with tone samples. For both groups, a food sample and a tone sample (tone-F) were associated with responding to one lever (e.g., stationary), and a no-food sample and a different tone sample (tone-NF) were associated with responding to the alternative lever (e.g., moving). During retention testing, we found equivalent forgetting for the food and no-food samples, but forgetting of the tone-F sample occurred more rapidly than forgetting of the tone-NF sample. This is the first MTO study to suggest that rats, like pigeons, may use hedonic samples as the basis for the common coding of nonhedonic samples in MTO delayed matching.

Frequency modulation detection as a measure of temporal processing: Age-related monaural and binaural effects

The detection of low-rate frequency modulation (FM) carried by a low-frequency tone has been employed as a means of assessing the fidelity of temporal fine structure coding. Detection of low-rate FM can be made more acute, relative to the monaural case, by the addition of a pure tone to the contralateral ear. This study examined whether FM detection in the 500-Hz region could be further improved by using a binaural stimulation mode where the modulator was antiphasic across the two ears. The study also sought to determine whether these dichotic FM conditions were beneficial in identifying the emergence of a temporal fine structure processing deficiency relatively early in the aging process. Young, mid-aged, and older listeners (n = 12 per group) were tested. The results demonstrated better FM acuity in the dichotic task irrespective of listener age. Dichotic FM detection also differentiated between age groups more definitively than diotic detection, especially in terms of distinguishing mid-aged from older listeners. In the group of older listeners, dichotic FM detection was weakly associated with absolute sensitivity to the carrier. In addition, this group failed to show a dichotic benefit in the presence of a marked asymmetry in sensation level across ears. The overall pattern of results suggests that dichotic FM measurements have advantages over monaural measurements for the purposes of assessing age-related temporal processing effects, although a marked asymmetry in absolute thresholds across ears could undermine these advantages.

Discrimination of Low-Frequency Tones Employs Temporal Fine Structure

An auditory neuron can preserve the temporal fine structure of a low-frequency tone by phase-locking its response to the stimulus. Apart from sound localization, however, much about the role of this temporal information for signal processing in the brain remains unknown. Through psychoacoustic studies we provide direct evidence that humans employ temporal fine structure to discriminate between frequencies. To this end we construct tones that are based on a single frequency but in which, through the concatenation of wavelets, the phase changes randomly every few cycles. We then test the frequency discrimination of these phase-changing tones, of control tones without phase changes, and of short tones that consist of a single wavelet. For carrier frequencies below a few kilohertz we find that phase changes systematically worsen frequency discrimination. No such effect appears for higher carrier frequencies at which temporal information is not available in the central auditory system.

Are higher-frequency sounds brighter in color and smaller in size? Auditory–visual correspondences in 10-month-old infants

Previous research has shown that not only adults but also two-and-a-half-year-old children associate higher-frequency sounds with smaller objects and with objects of brighter colors, suggesting that these intersensory correspondences are based on neural connections present very early in life. The present research examined whether 10-month olds are sensitive to these intersensory correspondences using a violation-of-expectation procedure. The results of Experiment 1 indicated that 10-month-olds associate a higher-frequency tone with an object of a brighter color and a lower-frequency tone with an object of a darker color. However, Experiment 2 found that 10-month olds did not always associate a higher-frequency tone with a smaller object and a lower-frequency tone with a larger object. The results suggest that infants have an initial bias to associate pitch with brightness, whereas pitch-size correspondences may be learned after birth by observing statistical co-occurrence patterns in the real world.

Detection of low‐frequency tones and whale predator sounds by the American sand lance Ammodytes americanus

Auditory evoked potentials (AEP) were used to measure the hearing range and auditory sensitivity of the American sand lance Ammodytes americanus. Responses to amplitude-modulated tone pips indicated that the hearing range extended from 50 to 400 Hz. Sound pressure thresholds were lowest between 200 and 400 Hz. Particle acceleration thresholds showed an improved sensitivity notch at 200 Hz but not substantial differences between frequencies and only a slight improvement in hearing abilities at lower frequencies. The hearing range was similar to Pacific sand lance Ammodytes personatus and variations between species may be due to differences in threshold evaluation methods. AEPs were also recorded in response to pulsed sounds simulating humpback whale Megaptera novaeangliae foraging vocalizations termed megapclicks. Responses were generated with pulses containing significant energy below 400 Hz. No responses were recorded using pulses with peak energy above 400 Hz. These results show that A. americanus can detect the particle motion component of low-frequency tones and pulse sounds, including those similar to the low-frequency components of megapclicks. Ammodytes americanus hearing may be used to detect environmental cues and the pulsed signals of mysticete predators.

Influence of lexical and acoustic context on phonetic categorization depends on listening situation

Phonetic categorization is influenced by multiple sources of contextual information, but little is known about how different sources of information interact. We examined the relative influence of lexical versus acoustic contexts on phonetic categorization of sounds along [s]-[S] continua embedded in word-nonword pairs (e.g., a[S]amed-a[s]amed, ca[s]ino-ca[S]ino). These categorization targets were preceded by sequences of 12 nonspeech tones with mean frequencies a standard deviation above or below the spectral means of the endpoint fricatives. Listeners’ [s]-[S] categorization was influenced by lexical information, exhibiting a Ganong effect with categorization shifted toward responses consistent with words, and also by acoustic context. The effect of the tone sequence was spectrally contrastive; there were more [S] responses (low spectral mean) following higher-frequency tones and more [s] responses (high spectral mean) following lower-frequency tones. In addition, the influence of acoustic relative to lexical context was modulated by listening environment. When the informational load of the lexical context was low (four word-nonword continua) acoustic context exerted a relatively greater influence than when the informational load of the lexical context was high (forty word-nonword continua). Multiple sources of context interact to influence phonetic categorization and the relative influence of different information sources is flexibly modulated by listening environment.

Temporal weighting for interaural time differences in low-frequency pure tones

In contrast to envelope-based interaural time differences (ITD) at high frequencies, where sound onsets play a dominant role, the reliability and salience fine-structure ITD at low frequency (<1500 Hz) suggests uniform sensitivity to information across periods of an ongoing stimulus waveform. Several past studies, however, have demonstrated low-frequency ITD thresholds to improve sub-optimally with increasing sound duration [e.g. Houtgast & Plomp 1968, JASA 44:807-12], suggesting that the initial periods of a brief tone play a greater role in ITD processing than do later periods. Here, we measured the temporal profile of ITD sensitivity in pure tones ranging from 250-1000 Hz. Sounds were presented with ITD that either remained fixed over the sound duration (condition RR) or progressed linearly to eliminate the ITD cue from either the beginning (condition 0R) or end (R0) of the sound. Durations varied from 40-640 ms, including 20 ms ramps applied diotically to minimize envelope cues. ITD detection thresholds demonstrated (a) suboptimal improvement with duration and (b) greater sensitivity to ITD available early (R0) rather than late (0R) in the stimulus, a pattern nearly identical to that observed for high-frequency envelope ITD. [Supported by NIH R01 DC011548.]

Rules Rule! Brain Activity Dissociates the Representations of Stimulus Contingencies with Varying Levels of Complexity

The significance of stimuli is linked not only to their nature but also to the sequential structure in which they are embedded, which gives rise to contingency rules. Humans have an extraordinary ability to extract and exploit these rules, as exemplified by the role of grammar and syntax in language. To study the brain representations of contingency rules, we recorded ERPs and event-related optical signal (EROS; which uses near-infrared light to measure the optical changes associated with neuronal responses). We used sequences of high- and low-frequency tones varying according to three contingency rules, which were orthogonally manipulated and differed in processing requirements: A Single Repetition rule required only template matching, a Local Probability rule required relating a stimulus to its context, and a Global Probability rule could be derived through template matching or with reference to the global sequence context. ERP activity at 200-300 msec was related to the Single Repetition and Global Probability rules (reflecting access to representations based on template matching), whereas longer-latency activity (300-450 msec) was related to the Local Probability and Global Probability rules (reflecting access to representations incorporating contextual information). EROS responses with corresponding latencies indicated that the earlier activity involved the superior temporal gyrus, whereas later responses involved a fronto-parietal network. This suggests that the brain can simultaneously hold different models of stimulus contingencies at different levels of the information processing system according to their processing requirements, as indicated by the latency and location of the corresponding brain activity.

Does crossmodal correspondence modulate the facilitatory effect of auditory cues on visual search?

The "pip-and-pop effect" refers to the facilitation of search for a visual target (a horizontal or vertical bar whose color changes frequently) among multiple visual distractors (tilted bars also changing color unpredictably) by the presentation of a spatially uninformative auditory cue synchronized with the color change of the visual target. In the present study, the visual stimuli in the search display changed brightness instead of color, and the crossmodal congruency between the pitch of the auditory cue and the brightness of the visual target was manipulated. When cue presence and cue congruency were randomly varied between trials (Experiment 1), both congruent cues (low-frequency tones synchronized with dark target states or high-frequency tones synchronized with bright target states) and incongruent cues (the reversed mapping) facilitated visual search performance equally, relative to a no-cue baseline condition. However, when cue congruency was blocked and the participants were informed about the pitch-brightness mapping in the cue-present blocks (Experiment 2), performance was significantly enhanced when the cue and target were crossmodally congruent as compared to when they were incongruent. These results therefore suggest that the crossmodal congruency between auditory pitch and visual brightness can influence performance in the pip-and-pop task by means of top-down facilitation.

THE PSYCHOPHYSICS OF LOW-FREQUENCY ACOUSTIC HEARING IN ELECTRIC AND ACOUSTIC STIMULATION (EAS) AND BIMODAL PATIENTS

This paper provides a review of the current literature on psychophysical properties of low-frequency hearing, both before and after implantation, with a focus on frequency selectivity, nonlinear cochlear processing, and speech perception in temporally modulated maskers for bimodal listeners as well as patients with hearing preservation in the implanted ear and receiving combined electric and acoustic stimulation (EAS). In this paper we review our work, the work of others, and report results not previously published for speech perception in steady-state and temporally fluctuating maskers; the degree of masking release and frequency resolution for 11 bimodal, 6 hearing preservation patients; and 5 control subjects with normal hearing. The results demonstrate that a small masking release is possible with acoustic hearing in just one ear, with the degree of masking release being correlated with the low-frequency pure tone average in the non-implanted ear; furthermore, frequency selectivity as defined by the width of the auditory filter was not correlated with the degree of masking release. Descriptions of the clinical utility of hearing preservation in the implanted ear for improving speech perception in complex listening environments, as well as directions for the future, are discussed.

The Role of Hearing Preservation on Electrical Thresholds and Speech Performances in Cochlear Implantation

The purpose of this study was to verify if the preservation of residual hearing after cochlear implantation in classic adult cochlear implant candidates implanted with a perimodiolar electrode correlates with the electric thresholds and with speech perception measures. Retrospective study. Cochlear Implant Center at a tertiary referral University Hospital. Forty-one patients with cochlear implant were involved in our study. They were subdivided into 2 groups according to the average preoperative hearing loss at the frequencies of 125 and 250 Hz (low-frequency pure tone average [LFPTA]). Group A included 21 patients with a mean LFPTA of 90 dB HL or lower; group B included 20 patients with a mean LFPTA of greater than 90 dB HL. They underwent 12 months' follow-up after cochlear implantation, including standard audiologic investigation, speech discrimination tests, and electrical measurements. No significant differences were found in speech perception tests among groups. In group A, hearing was preserved in 8 (group A1) and was lost in 13 patients (group A2); the postoperative LFPTA was significantly better (p < 0.0001) in A1. Group A1 patients present significantly higher C values (p < 0.0001) than the other 2 groups, and the dynamic range was therefore significantly wider (p < 0.001). Preservation of residual hearing should be attempted in all cases. In fact, although effects on the speech perception are not evident with the standard evaluation, larger electrical dynamic range can be achieved and may represent a sign of cochlear "well-being," potentially allowing a more complex electric stimulation of the nerve.

Differential group delay monitoring for high-speed data based on a low-frequency radio-frequency tone power measurement

A first-order polarisation mode dispersion (differential group delay (DGD)) monitoring technique using a low-speed detector for 40 Gb/s return to zero data transmission is proposed and experimentally demonstrated. The monitoring technique is based on adding an additional optical carrier which is frequency-shifted with respect to the data carrier at an orthogonal polarisation state. The added carrier beats with the data clock tones generating new RF tones at the photodetector output whose power depends on a sinusoidal function. By properly setting the frequency shift between optical carriers, a low-frequency radio-frequency (RF) tone is generated and used for DGD monitoring of high-speed data, providing a cost-effective solution, high resolution and wide monitoring range compared to traditional RF-tone-based DGD monitoring techniques. Experimental results show successful DGD monitoring from 0 to 25 ps with an RF-tone dynamic range of 18 dB. Insensitivity of the proposed technique to chromatic dispersion and optical signal-to-noise ratio is also demonstrated.

Low-frequency modulated quadratic and cubic distortion product otoacoustic emissions in humans

Previous studies have used low-frequency tones to modulate distortion product otoacoustic emissions (DPOAEs). The cubic DPOAE (CDPOAE) is mostly chosen because amplitudes sufficient for modulation can be evoked with moderate sound pressure levels. Quadratic DPOAEs (QDPOAEs) however, are more sensitive to minute changes of the cochlear operating point (OP) and are better suited to assess changes of the cochlear OP.Here, we compare the properties of low-frequency (30 Hz, 80–120 dB SPL) modulated CDPOAE and QDPOAEs evoked with f2 = 2 and 5 kHz in human subjects with normal hearing. The modulation depth was quantified with the modulation index (MI), a measure which considers both amplitude and phase.Modulated CDPOAEs evoked with f2 = 2 kHz have amplitude maxima at the zero crossings and amplitude minima at the extremes of the biasing tone (BT) which correlate positively with the BT level. CDPOAEs evoked with f2 = 5 kHz were recorded during biasing in exactly the same way as described before. At the highest BT levels used (120 dB SPL), very little modulation could be detected. Not only the depth, but also the shape of the QDPOAE modulation pattern is correlated with the BT level. At moderate BT levels (about 90–100 dB SPL) QDPOAEs evoked with f2 = 5 kHz show one amplitude notch around the zero crossing of the positive going flank of the BT (a single modulation pattern). At and above a BT level of about 105 dB SPL, the pattern reverses and shows a double modulation pattern. At the highest BT level used (120 dB SPL), quadratic MIs exceed cubic MIs (2.0 ± 0.5 and 0.97 ± 0.06, respectively).Patterns of low-frequency modulated QDPOAEs in humans are similar to the modulation seen in animal studies and as predicted by mathematical models. Human low-frequency modulated QDPOAEs are ideally suited to estimate cochlear OP shifts because of their high sensitivity to the OP shift.

Vestibular Hearing and Speech Processing

Vestibular hearing in human is evoked as a result of the auditory sensitivity of the saccule to low-frequency high-intensity tone. The objective was to investigate the relationship between vestibular hearing using cervical vestibular-evoked myogenic potentials (cVEMPs) and speech processing via word recognition scores in white noise (WRSs in wn). Intervention comprised of audiologic examinations, cVEMPs, and WRS in wn. All healthy subjects had detectable cVEMPs (safe vestibular hearing). WRSs in wn were obtained for them (66.9 ± 9.3% in the right ears and 67.5 ± 11.8% in the left ears). Dizzy patients in the affected ears, had the cVEMPs abnormalities (insecure vestibular hearing) and decreased the WRS in wn (51.4 ± 3.8% in the right ears and 52.2 ± 3.5% in the left ears). The comparison of the cVEMPs between the subjects revealed significant differences (P < 0.05). Therefore, the vestibular hearing can improve the speech processing in the competing noisy conditions.

Adaptive auditory plasticity for social communication in the plainfin midshipman fish (Porichthys notatus)

Acoustic communication plays an important role in the social behaviours of vocal teleost fishes in the family Batrachoididae (midshipman and toad fishes). The midshipman and toadfishes have become good models for investigating the neural and endocrine mechanisms of auditory perception and vocal production shared by all vertebrates (Bass and Lu 2006), in part, because the reproductive success of these batrachoidid fishes is highly dependent on acoustic communication. Recent neuroethological studies of acoustic communication in the plainfin midshipman fish (Porichthys notatus) have provided strong evidence for the related reproductive-state and steroid-dependent modulation of hearing sensitivity in this species that leads to enhanced coupling of sender and receiver in this communication system (Sisneros and Bass 2003; Sisneros et al. 2004a). The plainfin midshipman fish is a vocal marine teleost fish found along the west coast of the USA. During the late spring and summer, midshipman fish migrate from deep water into the rocky intertidal zone to court and spawn. Midshipman fish are known to have three adult reproductive morphs that include female and two male morphs known as type I and II. Type I or ‘singing’ males acoustically court females with their seasonal advertisement calls or ‘hums’, which is a multiharmonic acoustic signal with a fundamental frequency (F0) that ranges from 90 to 100Hz (Brantley and Bass 1994). The dominant harmonics of the hum range up to 400Hz and can contain as much or more spectral energy than the F0. These harmonics have been hypothesized to be important for the detection and localization of the advertisement signal during the reproductive season (Sisneros and Bass 2003). Type II males or ‘sneaker’ males use an alternative reproductive tactic that does not require them to build nests or acoustically court females. Instead type II males satellite and/or ‘sneak’ spawn in the nests of type I males to steal fertilizations from ‘singing’ males when they are actively courting females. Females rely heavily on their auditory sense to detect and locate advertising males that produce the multiharmonic hums during the breeding season and will often exhibit robust phonotaxis to a synthesized hum (and even to a low frequency tone near the F0 of the male’s advertisement call). Previous work showed that the frequency sensitivity of the auditory afferents that innervated the saccule, the main organ of hearing in the midshipman, changed seasonally with reproductive state such that reproductive females were better suited than nonreproductive females to encode the dominant harmonics of the male’s advertisement call (Sisneros and Bass 2003). An investigation of the seasonal periodicity of reproduction

Ultrasound detection in Clupeiform fishes

Event Abstract Back to Event Ultrasound detection in Clupeiform fishes Maria Wilson1* and David A. Mann1 1 University of South Florida, College of Marine Science, United States Clupeiform fishes belonging to the subfamily of Alosinae (shad and menhaden) detect and respond strongly to intense ultrasound (>20 kHz). When exposed to ultrasonic signals, Alosinae exhibit highly directional and intensity graded maneuvers, with faster response times and faster swimming speeds, as sound pressure levels increases. The ability to detect ultrasound in the members of the Alosinae is hypothesized to serve as an anti-predator response against echolocating toothed whales emitting ultrasonic clicks in the frequency range of 15 to 200 kHz and with intensities up to and above 220 dB re 1 µPa. It has been more than 15 years since the first discoveries of ultrasound sensitivity in Alosinae were reported. Despite the intervening years, the sensory organ responsibly for ultrasound detection has not yet been identified. Clupeiform fishes are unique in that they have specialized gas-filled bullae (extensions from the swim bladder) mechanically connected to both the ear (the utricle) and the lateral line via thin membranes, the bulla membrane and the lateral recess membrane, respectively. The gas-filled bullae-complex is found in all Clupeiform fishes; however only members of the subfamily of Alosinae have been found to detect ultrasonic signals. It has been hypothesized that the utricle of the inner ear is responsible for ultrasound detection through a specialized connection to the gas-filled bullae-complex, which shows a different suspension in the Alosinae compared to other Clupeiform fishes. Here we show that the lateral line and its connection to the gas-filled bullae-complex are important in ultrasound detection by Gulf menhaden. Mechanical manipulation of the lateral line system eliminates the ability of Gulf menhaden to detect ultrasound, but does not affect detection of a 600 Hz low frequency tone. We further show that the gas-filled bullae-complex vibrates in response to ultrasound and is the transducing element in ultrasound detection. These results add a new surprising dimension to the role of the lateral line and the bullae in Gulf menhaden, as the lateral line of fish previously has been believed only to detect low frequency hydrodynamic stimuli (<100 Hz). Further work on neuroanatomy and neural recordings from the lateral line and inner ear should elucidate the mechanism of ultrasound detection [Supported by Knud Højgaards Fondet and FNU]. Keywords: Alosinae, gas-filled bullae, Lateral Line, ultrasound detection Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster (but consider for participant symposium and student poster award) Topic: Sensory: Audition Citation: Wilson M and Mann DA (2012). Ultrasound detection in Clupeiform fishes. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00113 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 25 Apr 2012; Published Online: 07 Jul 2012. * Correspondence: Ms. Maria Wilson, University of South Florida, College of Marine Science, St. Petersburg, Florida, 33701, United States, im.maria.wilson@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Maria Wilson David A Mann Google Maria Wilson David A Mann Google Scholar Maria Wilson David A Mann PubMed Maria Wilson David A Mann Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Hearing thresholds for low-frequency complex tones of less than 150 Hz

Hearing thresholds for low-frequency complex tones of less than 150 Hz

Effects of inducer continuity on auditory stream segregation: Comparison of physical and perceived continuity in different contexts

The factors influencing the stream segregation of discrete tones and the perceived continuity of discrete tones as continuing through an interrupting masker are well understood as separate phenomena. Two experiments tested whether perceived continuity can influence the build-up of stream segregation by manipulating the perception of continuity during an induction sequence and measuring streaming in a subsequent test sequence comprising three triplets of low and high frequency tones (LHL-[ellipsis (horizontal)]). For experiment 1, a 1.2-s standard induction sequence comprising six 100-ms L-tones strongly promoted segregation, whereas a single extended L-inducer (1.1 s plus 100-ms silence) did not. Segregation was similar to that following the single extended inducer when perceived continuity was evoked by inserting noise bursts between the individual tones. Reported segregation increased when the noise level was reduced such that perceived continuity no longer occurred. Experiment 2 presented a 1.3-s continuous inducer created by bridging the 100-ms silence between an extended L-inducer and the first test-sequence tone. This configuration strongly promoted segregation. Segregation was also increased by filling the silence after the extended inducer with noise, such that it was perceived like a bridging inducer. Like physical continuity, perceived continuity can promote or reduce test-sequence streaming, depending on stimulus context.

Détection du micro-endommagement dans le tissu osseux trabéculaire par une méthode d’acousto-élasticité dynamique

Osteoporosis affects the whole skeleton strength leading to an actual fracture risk. Associated to a high level of morbidity, it is a critical public health issue. During the last decades, several X-rays and ultrasound devices have been developed to help the clinicians in their diagnosis. They are essentially related to bone mass while several factors are responsible for this pathology. Among them, microdamage has an interesting place. Nonlinear acoustic methods have already shown their ability to detect microcracks in different geophysical and industrial materials. We present a dynamic acousto-elastic testing (interaction of a very low frequency tone burst and high frequency pulses) to measure viscoelastic and dissipative nonlinearities. Applied to trabecular bone samples (human defatted calcanei), this method has shown a high level of nonlinearity in very dense regions of the calcanei. However, native microdamage is often at the limit of the method sensibility. To better evaluate this parameter, we have performed acousto-elastic measurements before and after inducing microdamage thanks to a compression fatigue test. We observed higher nonlinearity after induced damage. Moreover, the level of acoustic nonlinearity has been correlated to actual damage accumulation thanks to confocal microscopy analysis. However, acousto-elasticity measurements repeatability is weak. Correct reproducibility is observed for low level of nonlinearity (low level of microcracks). For high level of nonlinearity, quite different nonlinear behaviors are usually observed from one measurement to the next one.

On the differential diagnosis of Ménière’s disease using low-frequency acoustic biasing of the 2f1–f2 DPOAE

We have cyclically suppressed the 2f1–f2 distortion product otoacoustic emission (DPOAE) with low-frequency tones (17–97 Hz) as a way of differentially diagnosing the endolymphatic hydrops assumed to be associated with Ménière’s syndrome. Round-window electrocochleography (ECochG) was performed in subjects with sensorineural hearing loss (SNHL) on the day of DPOAE testing, and from which the amplitude of the summating potential (SP) was measured, to support the diagnosis of Ménière’s syndrome based on symptoms. To summarize and compare the cyclic patterns of DPOAE modulation in these groups we have used the simplest model of DPOAE generation and modulation, by assuming that the DPOAEs were generated by a 1st-order Boltzmann nonlinearity so that the magnitude of the 2f1-f2 DPOAE resembled the 3rd derivative of the Boltzmann function. We have also assumed that the modulation of the DPOAEs by the low-frequency tones was simply due to a sinusoidal change in the operating point on the Boltzmann nonlinearity. We have found the cyclic DPOAE modulation to be different in subjects with Ménière’s syndrome ( n = 16) when compared to the patterns in normal subjects ( n = 16) and in other control subjects with non-Ménière’s SNHL and/or vestibular disorders ( n = 13). The DPOAEs of normal and non-Ménière’s ears were suppressed more during negative ear canal pressure than during positive ear canal pressure. By contrast, DPOAE modulation in Ménière’s ears with abnormal ECochG was greatest during positive ear canal pressures. This test may provide a tool for diagnosing Ménière’s in the early stages, and might be used to investigate the pathological mechanism underlying the hearing symptoms of this syndrome.