Temporal aspects of suppression in distortion-product otoacoustic emissions.
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ABSTRACT:
SUBMITTER: Rodriguez J
PROVIDER: S-EPMC3108389 | biostudies-other | 2011 May
REPOSITORIES: biostudies-other
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Project description:Long-delay components showing a symmetrical pattern with positive and negative delays can be observed in the time-frequency representation (or in the inverse Fourier transform) of distortion product otoacoustic emissions. Positive-only phase-gradient delays are predicted by place-fixed backscattering mechanisms, such as coherent reflection due to roughness, whereas the nonlinear distortion wave-fixed mechanism should generate an almost null-delay component. The symmetrical delay pattern arises whenever spectral amplitude fluctuations are not fully correlated to phase fluctuations. An interpretation of this phenomenon is proposed, involving place-fixed modulation of the spectral strength of the wave-fixed nonlinear generator. Experimental data are shown in which these negative-delay sources are particularly strong, and further amplified by contralateral stimulation, suggesting that this effect could be dynamically enhanced. Analytical solutions of a linear 1-d transmission line model, in which cubic nonlinearity and roughness were added as small perturbations, have been used to test this hypothesis.
| S-EPMC5834380 | biostudies-literature
Project description:OBJECTIVES:The purpose of this study was to analyze distortion product otoacoustic emission (DPOAE) level and signal to noise ratio in a group of infants from birth to 4 months of age to optimize prediction of hearing status. DPOAEs from infants with normal hearing (NH) and hearing loss (HL) were used to predict the presence of conductive HL (CHL), sensorineural HL (SNHL), and mixed HL (MHL). Wideband ambient absorbance was also measured and compared among the HL types. DESIGN:This is a prospective, longitudinal study of 279 infants with verified NH and HL, including conductive, sensorineural, and mixed types that were enrolled from a well-baby nursery and two neonatal intensive care units in Cincinnati, Ohio. At approximately 1 month of age, DPOAEs (1-8?kHz), wideband absorbance (0.25-8?kHz), and air and bone conduction diagnostic tone burst auditory brainstem response (0.5-4?kHz) thresholds were measured. Hearing status was verified at approximately 9 months of age with visual reinforcement audiometry (0.5-4?kHz). Auditory brainstem response air conduction thresholds were used to assign infants to an NH or HL group, and the efficacy of DPOAE data to classify ears as NH or HL was analyzed using receiver operating characteristic (ROC) curves. Two summary statistics of the ROC curve were calculated: the area under the ROC curve and the point of symmetry on the curve at which the sensitivity and specificity were equal. DPOAE level and signal to noise ratio cutoff values were defined at each frequency as the symmetry point on their respective ROC curve, and DPOAE results were combined across frequency in a multifrequency analysis to predict the presence of HL. RESULTS:Single-frequency test performance of DPOAEs was best at mid to high frequencies (3-8?kHz) with intermediate performance at 1.5 and 2?kHz and chance performance at 1?kHz. Infants with a conductive component to their HL (CHL and MHL combined) displayed significantly lower ambient absorbance values than the NH group. No differences in ambient absorbance were found between the NH and SNHL groups. Multifrequency analysis resulted in the best prediction of HL for the SNHL/MHL group with poorer sensitivity values when infants with CHL were included. CONCLUSIONS:Clinical interpretation of DPOAEs in infants can be improved by using age-appropriate normative ranges and optimized cutoff values. DPOAE interpretation is most predictive at higher F2 test frequencies in young infants (2-8?kHz) due to poor test performance at 1 to 1.5?kHz. Multifrequency rules can be used to improve sensitivity while balancing specificity. Last, a sensitive middle ear measure such as wideband absorbance should be included in the test battery to assess possibility of a conductive component to the HL.
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Project description:This paper presents the results of simulating the acoustic suppression of distortion-product otoacoustic emissions (DPOAEs) from a computer model of cochlear mechanics. A tone suppressor was introduced, causing the DPOAE level to decrease, and the decrement was plotted against an increasing suppressor level. Suppression threshold was estimated from the resulting suppression growth functions (SGFs), and suppression tuning curves (STCs) were obtained by plotting the suppression threshold as a function of suppressor frequency. Results show that the slope of SGFs is generally higher for low-frequency suppressors than high-frequency suppressors, resembling those obtained from normal hearing human ears. By comparing responses of normal (100%) vs reduced (50%) outer-hair-cell sensitivities, the model predicts that the tip-to-tail difference of the STCs correlates well with that of intra-cochlear iso-displacement tuning curves. The correlation is poorer, however, between the sharpness of the STCs and that of the intra-cochlear tuning curves. These results agree qualitatively with what was recently reported from normal-hearing and hearing-impaired human subjects, and examination of intra-cochlear model responses can provide the needed insight regarding the interpretation of DPOAE STCs obtained in individual ears.
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Project description:Although animal models show a clear link between noise exposure and damage to afferent cochlear synapses, the relationship between noise exposure and efferent function appears to be more complex. Animal studies indicate that high intensity noise exposure reduces efferent medial olivocochlear (MOC) reflex strength, whereas chronic moderate noise exposure is associated with a conditioning effect that enhances the MOC reflex. The MOC reflex is predicted to improve speech-in-noise perception and protects against noise-induced auditory damage by reducing cochlear gain. In humans, MOC reflex strength can be estimated by measuring contralateral inhibition of distortion product otoacoustic emissions (DPOAEs). The objective of this study was to determine the impact of military noise exposure on efferent auditory function by measuring DPOAE contralateral inhibition in young Veterans and non-Veterans with normal audiograms. Compared with non-Veteran controls, Veterans with high levels of reported noise exposure demonstrated a trend of reduced contralateral inhibition across a broad frequency range, suggesting efferent damage. Veterans with moderate noise exposure showed trends of reduced inhibition from 3 to 4 kHz but greater inhibition from 1 to 1.5 kHz, consistent with conditioning. These findings suggest that, in humans, the impact of noise exposure on the MOC reflex differs depending on the noise intensity and duration.
| S-EPMC10857792 | biostudies-literature
Project description:Purpose Distortion product otoacoustic emissions (DPOAEs) and audiometric thresholds have been used to account for the impacts of subclinical outer hair cell (OHC) dysfunction on auditory perception and measures of auditory physiology. However, the relationship between DPOAEs and the audiogram is unclear. This study investigated this relationship by determining how well DPOAE levels can predict the audiogram among individuals with clinically normal hearing. Additionally, the impacts of age, noise exposure, and the perception of tinnitus on the ability of DPOAE levels to predict the audiogram were evaluated. Method Suprathreshold DPOAE levels from 1 to 10 kHz and pure-tone thresholds from 0.25 to 16 kHz were measured in 366 ears from 194 young adults (19-35 years old) with clinically normal audiograms and middle ear function. The measured DPOAE levels at all frequencies were used to predict pure-tone thresholds at each frequency. Participants were grouped by age, self-reported noise exposure/Veteran status, and self-report of tinnitus. Results Including DPOAE levels in the pure-tone threshold prediction model improved threshold predictions at all frequencies from 0.25 to 16 kHz compared with a model based only on sample mean pure-tone thresholds, but these improvements were modest. DPOAE levels for f 2 frequencies of 4 and 5 kHz were particularly influential in predicting pure-tone thresholds above 4 kHz. However, prediction accuracy varied based on participant characteristics. On average, predicted pure-tone thresholds were better than measured thresholds among Veterans, individuals with tinnitus, and the oldest age group. Conclusions These results indicate a complex relationship between DPOAE levels and the audiogram. Underestimation of pure-tone thresholds for some groups suggests that additional factors other than OHC damage may impact thresholds among individuals within these categories. These findings suggest that DPOAE levels and pure-tone thresholds may differ in terms of how well they reflect subclinical OHC dysfunction. Supplemental Material https://doi.org/10.23641/asha.13564745.
| S-EPMC10836814 | biostudies-literature
Project description:To study the possible involvement of energy-dependent mechanisms in the transduction of sound within the anuran ear, distortion product otoacoustic emissions (DPOAEs) were recorded in the northern leopard frog over a range of body temperatures. The effect of body temperature depended on the stimulus levels used and on the hearing organ under investigation. Low-level DPOAEs from the amphibian papilla (AP) were reversibly depressed for decreased body temperatures. Apparently, DPOAE generation in the AP depends on metabolic rate, indicating the involvement of active processes in the transduction of sound. In contrast, in the other hearing organ, the basilar papilla (BP), the effects of body temperature on DPOAEs were less pronounced, irrespective of the stimulus levels used. Apparently, metabolic rate is less influencing DPOAE generation. We interpret these results as evidence that no amplifier is involved in sound transduction in the BP. The passive functioning of the anuran BP would place this hearing organ in a unique position within tetrapod hearing, but may actually be beneficial to ectothermic species because it will provide the animal with a consistent spectral window, regardless of ambient or body temperature.
| S-EPMC2504610 | biostudies-other
Project description:It has previously not been possible to measure eardrum vibration of human subjects in the region of auditory threshold. It is proposed that such measurements should provide information about the status of the mechanical amplifier in the cochlea. It is this amplifier that is responsible for our extraordinary hearing sensitivity. Here, we present results from a laser Doppler vibrometer that we designed to noninvasively probe cochlear mechanics near auditory threshold. This device enables picometer-sized vibration measurements of the human eardrum in vivo. With this sensitivity, we found the eardrum frequency response to be linear down to at least a 20-dB sound pressure level (SPL). Nonlinear cochlear amplification was evaluated with the cubic distortion product of the otoacoustic emissions (DPOAEs) in response to sound stimulation with two tones. DPOAEs originate from mechanical nonlinearity in the cochlea. For stimulus frequencies, f1 and f2, with f2/f1 = 1.2 and f2 = 4-9.5 kHz, and intensities L1 and L2, with L1 = 0.4L(2) + 39 dB and L2 = 20-65 dB SPL, the DPOAE displacement amplitudes were no more than 8 pm across subjects (n = 20), with hearing loss up to 16 dB. DPOAE vibration was nonlinearly dependent on vibration at f2. The dependence allowed the hearing threshold to be estimated objectively with high accuracy; the standard deviation of the threshold estimate was only 8.6 dB SPL. This device promises to be a powerful tool for differentially characterizing the mechanical condition of the cochlea and middle ear with high accuracy.
| S-EPMC1780065 | biostudies-literature
Project description:Distortion-product otoacoustic emission (DPOAE) suppression data as a function of suppressor level (L(3)) for f(2) frequencies from 0.5 to 8 kHz and L(2) levels from 10 to 60 dB sensation level were used to construct suppression tuning curves (STCs). DPOAE levels in the presence of suppressors were converted into decrement versus L(3) functions, and the L(3) levels resulting in 3 dB decrements were derived by transformed linear regression. These L(3) levels were plotted as a function of f(3) to construct STCs. When f(3) is represented on an octave scale, STCs were similar in shape across f(2) frequency. These STCs were analyzed to provide estimates of gain (tip-to-tail difference) and tuning (Q(ERB)). Both gain and tuning decreased as L(2) increased, regardless of f(2), but the trend with f(2) was not monotonic. A roughly linear relation was observed between gain and tuning at each frequency, such that gain increased by 4-16 dB (mean ≈ 5 dB) for every unit increase in Q(ERB), although the pattern varied with frequency. These findings suggest consistent nonlinear processing across a wide frequency range in humans, although the nonlinear operation range is frequency dependent.
| S-EPMC3070996 | biostudies-other
Project description:The reliability of distortion-product otoacoustic emission (DPOAE) measurements and their relation to loudness measurements was examined in 16 normal-hearing subjects and 58 subjects with hearing loss. The level of the distortion product (L(d)) was compared across two sessions and resulted in correlations that exceeded 0.90. The reliability of DPOAEs was less when parameters from nonlinear fits to the input/output (I/O) functions were compared across visits. Next, the relationship between DPOAE I/O parameters and the slope of the low-level portion of the categorical loudness scaling (CLS) function (soft slope) was assessed. Correlations of 0.65, 0.74, and 0.81 at 1, 2, and 4 kHz were observed between CLS soft slope and combined DPOAE parameters. Behavioral threshold had correlations of 0.82, 0.83, and 0.88 at 1, 2, and 4 kHz with CLS soft slope. Combining DPOAEs and behavioral threshold provided little additional information. Lastly, a multivariate approach utilizing the entire DPOAE I/O function was used to predict the CLS rating for each input level (dB SPL). Standard error of the estimate when using this method ranged from 2.4 to 3.0 categorical units (CU), suggesting that DPOAE I/O functions can predict CLS measures within the CU step size used in this study (5).
| S-EPMC3292604 | biostudies-other
Project description:BackgroundStudies on animals have demonstrated that maternal iron deficiency anaemia (IDA) could result in decreased cochlear sensory hair cells and reduced amplitudes of distortion-product otoacoustic emissions (DPOAEs) of young guinea pigs. Thus, it is essential to study the functioning of cochlear hair cells using DPOAEs in human newborn babies with maternal IDA. The current study explores maternal IDA's effect on DPOAEs in newborn babies.MethodA total of 110 newborn babies with gestational age ≥34 weeks were considered and a 'between-subjects' design was used. The participants were divided into 3 groups- "Normal" (61 babies without maternal IDA), "Mild" (28 babies with mild maternal IDA) and "Moderate" (21 babies with moderate maternal IDA). The cord blood was collected and the DPOAEs were recorded for each baby for a range of frequencies (1 k - 8 kHz) and a range of intensities (70-40 dB SPL in 10 dB steps).ResultsThe analysis of both DP-gram and DP input-output (I/O) function showed that there was no significant difference (p > 0.05) across the normal, mild, and moderate groups in the overall presence of DPOAEs as well as the amplitude across frequencies or intensities (70-40 dB SPL). Also, the overall correlation of RBC indices with DPOAE amplitude across frequencies as well as the slope of the I/O function showed no relationship.ConclusionThe current study concludes that there is no effect of late-term maternal IDA on the DPOAEs of newborn babies.
| S-EPMC10366579 | biostudies-literature