Presence Of Spontaneous Otoacoustic Emissions Research Articles

Extended High Frequency Thresholds and Their Relationship to Distortion Product Otoacoustic Emissions, Hearing Acuity, Age, Gender, Presence of Spontaneous Otoacoustic Emissions, and Side of Measurement

Hearing is normally evaluated up to 8 kHz, even though testing can easily be performed at higher frequencies (up to 16 or 20 kHz). The range beyond 8 kHz is often referred to as the extended high frequency (EHF) range. This study aimed to explore the relationship between EHF hearing thresholds (HTs) and distortion product otoacoustic emissions (DPOAEs) in adult subjects. Also of interest were the effects of the presence of spontaneous otoacoustic emissions (SOAEs), gender, ear side, and age. The main finding was that DPOAEs, both within the standard frequency (SF) range (0.125–8 kHz) and the EHF range (10–16 kHz), decrease as thresholds deteriorate. For both ranges, DPOAEs and HTs depend on age, even for those with normal hearing, although EHFs seem to be especially affected by age. The presence of SOAEs was the only other factor that significantly influenced DPOAE level. For both DPOAEs and HTs, only minor and non-significant effects were related to gender and ear side. It was concluded that DPOAEs in the EHF range appear to be good predictors of EHF HTs. Moreover, since DPOAEs and HTs in the EHF range both correlate with age, these two measures may be suitable markers for incipient presbycusis.

Cochlear Function in Individuals with and without Spontaneous Otoacoustic Emissions.

This study investigated the status of spontaneous otoacoustic emissions (SOAEs) on cochlear function in a cohort of male/female participants with a wide age range. It examined whether there was a correlation between the presence of SOAEs and measurements of transient evoked otoacoustic emissions (TEOAEs), distortion product otoacoustic emissions (DPOAEs), SOAEs and extended high-frequency (EHF) hearing thresholds. 463 participants (222 male, 241 female; age range 20-59 years) with pure-tone thresholds ≤25 dB HL for octave frequencies of 500-8000 Hz were included in the study, divided into three age groups (20-29, 30-39, and 40-59 years). Evaluations included EHF (9000-16,000 Hz) hearing thresholds and TEOAE, DPOAE and SOAE measures. Multiple regression models showed that participants with SOAEs had larger expected amplitudes and signal-to-noise ratios (SNRs) for TEOAE and DPOAE responses than participants without SOAEs, holding gender and age variables constant. Spearman correlation tests identified deterioration in TEOAE and DPOAE amplitudes and SNRs, and EHF hearing thresholds with age in participants without SOAEs. Among participants with SOAEs, no significant decreases in TEOAE and DPOAE measures were shown in participants with older age. Nonetheless, as expected, EHF hearing thresholds did become worse with age, with or without SOAEs. Participants with identifiable SOAEs had greater TEOAE and DPOAE amplitudes and SNRs than participants without SOAEs. SOAEs appear to be a useful marker of cochlear health in adults.

KURTOZA (SPEKTRALNA) SYGNAŁU EMISJI OTOAKUSTYCZNYCH Z POMOCĄ TRANSFORMACJI HUSIMI’EGO – BADANIE PILOTAŻOWE

BackgroundTime-frequency distributions can help reveal resonant modes of OAEs. The Husimi transform is the time-frequency distribution of probability. The sound pressure probability density function for a given frequency can be derived from the Husimi transform. Using the Husimi transform as the weight function, it is possible to define the spectral kurtosis of OAEs.Material and MethodsThe Husimi transform was calculated numerically from OAE data recorded from subjects with normal hearing. We examined click-evoked OAEs (CEOAEs) and tone-burst-evoked OAEs (TBOAEs) with stimuli centered at 1, 2, and 4 kHz, and the presence of spontaneous OAEs (SOAEs) was also investigated. The aim of this study was to examine the statistical properties of otoacoustic emissions (OAEs) and relate them to resonant modes of the cochlea. Assuming that the probability of the sound pressure of an OAE at any time and frequency is given by a Husimi-type transform, we analyzed statistical features of the probability distribution, particularly spectral kurtosis.ResultsWith evoked OAEs, a minimum in kurtosis was found at frequencies close to SOAEs. With TBOAEs, three sorts of SOAEs were found: those with high positive kurtosis, those with small positive kurtosis, and those with negative kurtosis; in these cases, SOAEs appeared at the same frequency as the kurtosis minimum.ConclusionsThe kurtosis of evoked components of an OAE is strongly affected by the presence of an SOAE. The number of positive peaks and negative troughs of spectral kurtosis in a given frequency band seem to be characteristic of each subject. It is suggested that a new way of distinguishing types of OAEs may involve calculating the spectral kurtosis, and this may be diagnostically useful.

Time–frequency analysis of linear and nonlinear otoacoustic emissions and removal of a short-latency stimulus artifact

Click-evoked otoacoustic emissions (CEOAEs) are commonly recorded as average responses to a repetitive click stimulus. If the click train has constant polarity, a linear average results; if it contains a sequence of clicks of differing polarity and amplitude, a nonlinear average can be calculated. The purpose of this study was to record both protocols from the same set of ears and characterize the differences between them. The major features of CEOAEs were similar under both protocols with the exception of a region spanning 0-5 ms in time and 0-2.2 kHz in frequency. It was assumed that the signal derived from the linear protocol was contaminated by stimulus artifact, and so a simple procedure was used--involving high-pass filtering and time-windowing--to remove components of this artifact. This procedure preserved the short-latency, high-frequency responses; it also produced a marked similarity in the time-frequency plots of recordings made under the two protocols. This result means it is possible to take advantage of the better signal-to-noise ratio of the linear data compared to its nonlinear counterpart. Additionally, it was shown that CEOAEs recorded under the linear protocol appear to be less dependent on the presence of spontaneous otoacoustic emissions (SOAEs).

An investigation into the relationship between input–output nonlinearities and rate-induced nonlinearities of click-evoked otoacoustic emissions recorded using maximum length sequences

The maximum length sequence (MLS) technique allows otoacoustic emissions (OAEs) to be recorded using clicks presented at very high presentation rates. It has previously been found that increasing the click presentation rate leads to increasing suppression (termed “rate-suppression”) of the MLS evoked OAE (Hine, J.E., Thornton, A.R.D., 1997. Transient evoked otoacoustic emissions recorded using maximum length sequences as a function of stimulus rate and level. Ear Hear. 18, 121–128). It has been suggested that the source of rate-suppression arises from the same nonlinear processes that give rise to the well-known nonlinear growth of OAEs. Based on this assumption, a simple model of rate-suppression (Kapadia, S., Lutman, M.E., 2001. Static input–output nonlinearity as the source of nonlinear effects in maximum length sequence click-evoked OAEs. Br. J. Audiol. 35, 103–112) predicts that both input–output (I/O) nonlinearity and rate-suppression can be unified by characterising the stimulus in terms of its acoustic power which, at high rates, is proportional to the click presentation rate. The objective of this study was to test this simple model by recording MLS OAEs from a group of normally hearing adults over a range of stimulus rates from 40 to 5000 clicks/s, and of stimulus levels from 45 to 70 dB peSPL. The results are broadly in agreement with the predictions from the model, though there appears to be some tendency for the model to slightly overestimate the degree of rate-suppression for a given degree of I/O nonlinearity. It is also suggested that the model may break down more significantly in the presence of spontaneous OAEs.

Influence of spontaneous otoacoustic emissions on distortion product otoacoustic emission amplitudes

Although the influence of the levels and ratios of the primary stimulus on the amplitude of distortion product otoacoustic emissions (DPOAEs) has been studied intensely, the influence of the presence of spontaneous otoacoustic emissions (SOAEs) has been investigated less thoroughly. The present investigation analysed whether the unilateral presence of 58 SOAEs in 43 normal-hearing adults was related to larger DPOAEs in the ear with SOAEs compared to the contralateral ear having no SOAEs. The study was designed such that the only factor that could influence the amplitude of DPOAEs was the presence of SOAEs. Input/output ( I/ O) functions were collected in response to primary tones that were presented in 5-dB steps from 70 to 40 dB SPL at the frequency of the unilaterally recorded SOAE of each subject. The primary outcome was the demonstration of statistically significant ( P<0.05) larger DPOAEs in ears exhibiting SOAEs than in ears without measurable SOAEs, except at the highest stimulus level of 70 dB SPL. These results suggest that SOAEs play an additive role in the measurement of DPOAEs. The enhancing effect of the unilateral presence of SOAEs on DPOAEs was statistically significant for 65 dB SPL and lower levels of primary tones. The authors speculate that passive cochlear properties begin to participate in the generation of DPOAEs at primary-stimulus levels greater than 65 dB SPL.

Influence of handedness on peripheral auditory asymmetry.

It is well established that in humans many differences between right- and left-handers, anatomical, physiological and functional, exist. Left- and mixed-handedness is associated with greater bihemispheric representation of cognitive functions than in right-handers. Several studies indicate a left-right asymmetry in the function of hearing pathways between cochlea and auditory cortex, and furthermore, that this asymmetry is associated with handedness. Our investigation focuses on the medial olivo-cochlear system, which has been demonstrated to be more effective in the right than left ear in right-handers. The aim of the study was to investigate this auditory efferent system asymmetry according to handedness, gender, eyedness, footedness and the presence of spontaneous otoacoustic emissions. The medial efferent system has been found to be more effective in the right than left ear in right-handers, while functioning symmetrically in left-handers. Furthermore, the olivo-cochlear system, assumed to be involved in basic language processing, shows an asymmetrical pattern of functioning influenced by handedness as well as by hemispheric language representation. Reverse medial efferent system asymmetry was observed in left-handers compared to that in right-handers, on condition that only left-handed males were considered, or that the left-handers were also left-eyed, or that spontaneous otoacoustic emissions were present in the left ear of the left-handers, or when only left-handers without mixed-handers were considered.

Ear canal reflectance in the presence of spontaneous otoacoustic emissions. I. Limit-cycle oscillator model.

Allen et al. [Abstract in Eighteenth Midwinter Research Meeting of the Association for Research in Otolaryngology, Des Moines, IA (1995)] have found that the ear canal reflectance passes through a minimum around the frequency of a spontaneous otoacoustic emission (SOAE). They considered this result to constitute evidence against active nonlinear cochlear function as the basis for SOAEs. In order to investigate theoretically the expected behavior of ear canal reflectance in the neighborhood of a SOAE associated with an active-nonlinear cochlea, we use a simplified model in which the ear drum end of the ear canal is effectively terminated by a nonlinear-active element. Under the influence of a sinusoidal driver at the entrance of the ear canal, this element will, to a good approximation, either (1) oscillate at both the frequency of the driver (at which the reflectance is determined) and the SOAE (at a suppressed level, corresponding to nonentrainment), or (2) be entrained and only oscillate at the driving frequency. The magnitude of the nonlinear ear canal reflectance is found to exceed unity only at sufficiently low stimulus levels, and occurs under conditions of entrainment and nonentrainment of the spontaneous emission. Otherwise, the reflectance is less than unity and, as a function of frequency, has a minimum around the SOAE frequency.

All-pole representation of the cochlear input impedance, modal representation of the ear canal signal, and reflectance in the ear canal in the presence of spontaneous otoacoustic emissions

The cochlear input impedance associated with the linear active component of cochlear mechanics is represented as an all-pole function of frequency. This allows the dynamics of the ear canal signal to be expressed in terms of the behavior of coupled damped harmonic oscillators. Spontaneous otoacoustic emissions correspond to negative damping and, consequently, unstable oscillations. The introduction of a compressive nonlinearity, which stabilizes the spontaneous emissions, gives an interesting and computationally simple model for investigating the response of the auditory periphery in the case where there are one or more spontaneous emissions. The model is used, in particular, for studying the behavior of the reflectance in the ear canal. The magnitude of the reflectance will normally be less than one due to the entrainment of the emissions.

Distortion-product otoacoustic emissions in the bobtail lizard. I: General characteristics

In the ear canal of the bobtail lizard, both emitted harmonics and distortion products (DP) were measured, some of which were sensitive to hypoxia. The minimal levels of primary tones for the production of DP corresponded closely to the best auditory-nerve fiber thresholds for this lizard species. DP originating from the two segments of the basilar papilla (which respond to different frequency ranges) differed in a number of respects. DP from the higher-frequency segment bore a remarkable resemblance to the acoustic DP of mammals in many details, in spite of substantial structural and micromechanical differences between these hearing organs, suggesting that it is the characteristics of the hair cells themselves that are the most important factors determining DP generation. Also, DP clearly originated in the high-frequency region of this lizard papilla, where single-nerve fibers do not show two-tone rate suppression, another nonlinear phenomenon. In some cases, the DP level was clearly affected by the presence of spontaneous otoacoustic emissions. The frequency selectivity of the DP 2 f1−f2 and 2 f2−f1 in the bobtail lizard was also studied, by measuring thresholds of DP detection while varying the frequency ratio of the primary tones. The characteristics of tuning in high-frequency DP showed some remarkable similarities to the tuning curves of single-nerve fibers, suggesting that the characteristics of acoustic DP produced by low-level primary tones were determined by the tuning characteristics of the hearing organ at the hair-cell level.