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1.
J Am Acad Audiol ; 30(6): 459-471, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30461415

RESUMO

BACKGROUND: The relationship between type-1 diabetes mellitus (DM) and cochlear dysfunction remains inconclusive. PURPOSE: The purpose of this study was to examine otoacoustic emissions (OAEs) in normal-hearing young adults with type-1 DM as compared with matched controls and identify potential covariates influencing OAE findings. RESEARCH DESIGN: Cross-sectional study. STUDY SAMPLE: N = 40 young adults aged 18-28 years including individuals with type-1 DM (n = 20) and age-gender matched controls (n = 20) with normal hearing sensitivity. DATA COLLECTION AND ANALYSIS: Measures of pure-tone threshold sensitivity and OAEs, including distortion product otoacoustic emissions (DPOAEs), transient evoked OAEs, and DPOAE fine structure, were compared between groups. Covariates such as noise exposure and DM-related factors (e.g., duration of disease, glycated hemoglobin levels) were considered. Statistical analysis included analysis of variance and linear regression. RESULTS: Measures of hearing sensitivity and auditory function in both groups were comparable for all assays, except DPOAE fine structure. A reduced number of fine structure peaks and component amplitudes were found in the type-1 diabetes DM group with the primary difference in the reflection component. CONCLUSIONS: The results indicate that reduced cochlear function in young adults with type-1 DM can be revealed using DPOAE fine structure, suggesting potential clinical applications of DPOAE fine structure in early identification of cochlear pathology. Potential factors underlying these findings are discussed.


Assuntos
Limiar Auditivo/fisiologia , Cóclea/fisiopatologia , Diabetes Mellitus Tipo 1/fisiopatologia , Perda Auditiva Neurossensorial/fisiopatologia , Emissões Otoacústicas Espontâneas/fisiologia , Adolescente , Adulto , Audiometria de Tons Puros , Estudos Transversais , Diabetes Mellitus Tipo 1/complicações , Feminino , Perda Auditiva Neurossensorial/diagnóstico , Perda Auditiva Neurossensorial/etiologia , Humanos , Masculino , Adulto Jovem
2.
J Assoc Res Otolaryngol ; 18(1): 121-138, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27796594

RESUMO

The reported research introduces a noninvasive approach to estimate round-trip outer-middle ear pressure gain using distortion product otoacoustic emissions (DPOAEs). Our ability to hear depends primarily on sound waves traveling through the outer and middle ear toward the inner ear. The role of the outer and middle ear in sound transmission is particularly important for otoacoustic emissions (OAEs), which are sound signals generated in a healthy cochlea and recorded by a sensitive microphone placed in the ear canal. OAEs are used to evaluate the health and function of the cochlea; however, they are also affected by outer and middle ear characteristics. To better assess cochlear health using OAEs, it is critical to quantify the effect of the outer and middle ear on sound transmission. DPOAEs were obtained in two conditions: (i) two-tone and (ii) three-tone. In the two-tone condition, DPOAEs were generated by presenting two primary tones in the ear canal. In the three-tone condition, DPOAEs at the same frequencies (as in the two-tone condition) were generated by the interaction of the lower frequency primary tone in the two-tone condition with a distortion product generated by the interaction of two other external tones. Considering how the primary tones and DPOAEs of the aforementioned conditions were affected by the forward and reverse outer-middle ear transmission, an estimate of the round-trip outer-middle ear pressure gain was obtained. The round-trip outer-middle ear gain estimates ranged from -39 to -17 dB between 1 and 3.3 kHz.


Assuntos
Orelha Externa/fisiologia , Orelha Média/fisiologia , Emissões Otoacústicas Espontâneas/fisiologia , Adulto , Feminino , Humanos , Masculino , Pressão , Razão Sinal-Ruído
3.
Hear Res ; 328: 157-65, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26318364

RESUMO

Distortion product otoacoustic emissions (DPOAE) in newborns and adults were evoked by sweeping primaries up and down in frequency at 1 s/octave. Sweeping up and down in frequency resulted in changes in the amplitude vs. frequency functions of the composite DPOAE and its two major components. In addition, DPOAE component phases differed slightly between the up- and down-swept conditions. The changes in amplitude vs. frequency functions were quantified using a covariate correlation technique, yielding single-valued estimates of the magnitude of the frequency changes. Separate analyses were performed for the entire DPOAE frequency range and split into low and high frequency ranges. There were consistent changes in newborn and adult composite DPOAEs and reflection components, but not generator components. Adults had significant frequency changes in the composite DPOAE for all frequency ranges and in the reflection component for the entire frequency range. Newborns had significant frequency change in the reflection component for all frequency ranges. Differences in frequency change between adults and newborns may stem from developmental changes in cochlear processing. Alignment of the component phase differences between the up- and down-swept conditions resulted in elimination of frequency-change in reconstructed composite DPOAEs.


Assuntos
Cóclea/fisiologia , Emissões Otoacústicas Espontâneas/fisiologia , Estimulação Acústica , Adulto , Audiometria , Calibragem , Feminino , Testes Auditivos , Humanos , Recém-Nascido , Análise dos Mínimos Quadrados , Masculino , Reprodutibilidade dos Testes
4.
Ear Hear ; 36(6): 695-704, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26049553

RESUMO

OBJECTIVES: Distortion product otoacoustic emissions (DPOAEs), a by-product of normal outer hair cell function, are used in research and clinical settings to noninvasively test cochlear health. The composite DPOAE recorded in the ear canal is the result of interactions of at least two components: a nonlinear distortion component (the generator component) and a linear reflection component. Negative middle ear pressure (NMEP) results in the tympanic membrane being pulled inward and increases middle ear impedance. This influences both the forward travel of stimuli used to induce distortion products and the reverse travel of the emissions back to the ear canal. NMEP may therefore limit the effectiveness of DPOAEs in clinical settings. DESIGN: Twenty-six normal-hearing subjects were recruited, and eight were able to reliably and consistently induce NMEP using the Toynbee maneuver. Eight interleaved measures of tympanic peak pressure (TPP) were collected for each subject at normal pressure and NMEP. DPOAEs were then collected both when middle ear pressure was normal and during subject-induced NMEP. All measures were interleaved. Two primary tones were swept logarithmically across frequency (1 second per octave) from f1 = 410 to 6560 Hz and f2 = 500 to 8000 Hz (f1/f2 = 1.22), producing 2f1 - f2 DPOAEs from 320 to 5120 Hz. DPOAEs were collected at three equal-level primary level combinations (L65, L70, L75 dB SPL). Before composite and component DPOAE analysis, analysis of the f1 DPOAE primary confirmed that subjects had successfully induced NMEP. DPOAE and component magnitudes were separately analyzed using repeated measures analysis of variances with three factors, primary level (L65, L70, L75 dB SPL), middle ear pressure (normal pressure versus NMEP), and frequency (500 to 4000 Hz). RESULTS: Mean subject-induced NMEP ranged from -65 to -324 daPa. Changes in the magnitude (dB) of the primary tones used to induce the DPOAE provided a reliable indicator of subject-induced NMEP. Composite DPOAE and component levels were significantly affected by NMEP for all the frequencies tested. Changes were most clearly observed for the generator component with one subject demonstrating a mean decrease of 12 dB in magnitude during NMEP. Results were subject-specific, and there was a correlation between the degree of negative TPP induced and the amount of change in DPOAE level. CONCLUSIONS: Mean TPPs collected during NMEP ranged from -65 to -324 daPa and significantly affected composite DPOAE, generator, and reflection component levels. Changes in the magnitude of the swept-primaries as a function of frequency were used to confirm that NMEP had been successfully induced. The patterns of change in the composite DPOAEs were clearer and easier to interpret when the components of the DPOAE were separated with evaluation of the generator component alone.


Assuntos
Orelha Média , Células Ciliadas Auditivas Externas/fisiologia , Emissões Otoacústicas Espontâneas/fisiologia , Pressão , Impedância Elétrica , Voluntários Saudáveis , Humanos
5.
J Acoust Soc Am ; 136(1): 272-83, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24993213

RESUMO

The measurement of efferent-induced suppression of otoacoustic emissions (OAEs) using contralateral acoustic stimulation (CAS) is complicated by potential contamination by the middle ear muscle reflex (MEMR), particularly at moderate to high CAS levels. When logarithmically sweeping primaries are used to measure distortion product otoacoustic emissions, the level and phase of the primaries at the entrance of the ear canal may be monitored simultaneously along with the OAEs elicited by the swept-tones. A method of detecting MEMR activation using swept-tones is presented in which the differences in the primaries in the ear canal with and without CAS are examined, permitting evaluation of MEMR effects over a broad frequency range. A range of CAS levels above and below expected contralateral acoustic reflex thresholds permitted evaluation of conditions with and without MEMR activation.


Assuntos
Contração Muscular , Emissões Otoacústicas Espontâneas , Reflexo Acústico , Tensor de Tímpano/inervação , Estimulação Acústica , Acústica , Limiar Auditivo , Humanos , Processamento de Sinais Assistido por Computador , Espectrografia do Som , Fatores de Tempo
6.
J Acoust Soc Am ; 129(4): 2068-79, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21476662

RESUMO

Medial olivocochlear (MOC) efferent fibers synapse directly on the outer hair cells (OHCs). Efferent activation evoked by contralateral acoustic stimulation (CAS) will affect OHC amplification and subsequent measures of distortion-product otoacoustic emissions (DPOAEs). The aim of this study was to investigate measures of total and separated DPOAEs during efferent activation. Efferent activation produces both suppression and enhancement of the total DPOAE level. Level enhancements occurred near fine-structure minima and were associated with consistent MOC evoked upward shifts in DPOAE fine-structure frequency. Examination of the phase of the separated components revealed that frequency shifts stemmed from increasing phase leads of the reflection component during CAS, while the generator component phase was nearly invariant. Separation of the two DPOAE components responsible for the fine-structure revealed more consistent reduction of the levels of both components. Using vector subtraction (which takes into account both level and phase) to estimate the changes in the unseparated DPOAE provided consistent evidence of DPOAE suppression. Including phase information provided a more sensitive, valid and consistent estimate of CAS function even if one does not know the position of the DPOAE in the fine-structure.


Assuntos
Acústica , Audiologia/métodos , Percepção Auditiva/fisiologia , Células Ciliadas Auditivas Externas/fisiologia , Emissões Otoacústicas Espontâneas/fisiologia , Estimulação Acústica , Adulto , Limiar Auditivo/fisiologia , Núcleo Coclear/fisiologia , Meato Acústico Externo/fisiologia , Humanos , Núcleo Olivar/fisiologia , Adulto Jovem
7.
Hear Res ; 277(1-2): 107-16, 2011 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-21376109

RESUMO

The presence of tinnitus often coincides with hearing loss. It has been argued that reduced peripheral input leads to frequency-specific increase in neuronal gains resulting in tinnitus-related hyper-activity. Following this gain-adaptation hypothesis, impaired cochlear function should be predictive of the presence and spectral characteristics of tinnitus. To assess cochlear function, perceptual thresholds and distortion product otoacoustic emissions (DPOAEs) were measured with high frequency resolution for subjects with tinnitus and non-tinnitus control subjects (N = 29 and N = 18) with and without hearing loss. Subjects with tinnitus also provided a 'tinnitus likeness spectrum' by rating the similarity of their tinnitus to tones at various frequencies. On average, subjects with tinnitus had elevated thresholds, reduced DPOAE, and increased slope of the DPOAE input-output function in the range from 4 to 10 kHz. These measures were strongly correlated and were equally predictive of the presence of tinnitus. Subjects with a pronounced edge to their hearing loss profile were very likely to have tinnitus. In the group average, the tinnitus likeness spectrum was correlated with perceptual thresholds (r = 0.98, p < 0.01), confirming previous reports. For 19 of 29 of subjects, perceptual thresholds were correlated with the tinnitus likeness ratings across frequencies and this correlation was significantly improved when low input-level DPOAE were included as an additional variable (r = 0.83 ± 0.09, N = 19). Thus, cochlear function is strongly associated with the tinnitus percept and measures of cochlear function using DPOAEs provide additional diagnostic information over perceptual thresholds alone.


Assuntos
Percepção Auditiva , Cóclea/fisiopatologia , Perda Auditiva/fisiopatologia , Emissões Otoacústicas Espontâneas , Processamento de Sinais Assistido por Computador , Zumbido/fisiopatologia , Estimulação Acústica , Adaptação Fisiológica , Adulto , Audiometria de Tons Puros , Limiar Auditivo , Estudos de Casos e Controles , Feminino , Perda Auditiva/diagnóstico , Humanos , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Psicoacústica , Espectrografia do Som , Zumbido/diagnóstico
8.
J Acoust Soc Am ; 129(2): 792-800, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21361438

RESUMO

Distortion product otoacoustic emission (DPOAE) fine structure is due to the interaction of two major components coming from different places in the cochlea. One component is generated from the region of maximal overlap of the traveling waves generated by the two primaries and is attributed to nonlinear distortion (nonlinear component). The other component arises predominantly from the tonotopic region of the distortion product and is attributed to linear coherent reflection (reflection component). Aspirin (salicylate) ototoxicity can cause reversible hearing loss and reduces otoacoustic emission generation in the cochlea. The two components are expected to be affected differentially by cochlear health. Changes in DPOAE fine structure were recorded longitudinally in three subjects before, during, and after aspirin consumption. Full data sets were analyzed for two subjects, but only partial data could be analyzed from the third subject. Resulting changes in the two components of DPOAE fine structure revealed variability among subjects and differential effects on the two components. For low-intensity primaries, both components were reduced with the reflection component being more vulnerable. For high-intensity primaries, the nonlinear component showed little or no change, but the reflection component was always reduced.


Assuntos
Aspirina/toxicidade , Cóclea/efeitos dos fármacos , Perda Auditiva/induzido quimicamente , Modelos Biológicos , Emissões Otoacústicas Espontâneas/efeitos dos fármacos , Estimulação Acústica , Adulto , Aspirina/administração & dosagem , Audiometria , Limiar Auditivo , Cóclea/fisiopatologia , Análise de Fourier , Perda Auditiva/fisiopatologia , Humanos , Análise dos Mínimos Quadrados , Dinâmica não Linear , Tempo de Reação , Fatores de Tempo , Adulto Jovem
9.
Hear Res ; 269(1-2): 180-5, 2010 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-20600743

RESUMO

The hearing status of an experimental animal is typically assessed in the laboratory setting by the combined use of auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAEs), carried out in succession, with the former assay preceding the latter. This study reports a cautionary finding that the use of this accepted regimen yields a reduced DPOAE response. When the DPOAEs were performed after ABR testing, transient reduction of the DPOAE amplitudes was observed at all frequencies in both the inbred, C57/B6 and FVB/N, and the outbred, SW mouse strains. DPOAEs were reduced post-ABR in multiple mouse strains which suggests that this finding is not strain-specific but a general consequence of the preceding ABR analysis. The reduction in DPOAE was temporary: when re-tested at one hour, DPOAE amplitudes recovered to pre-ABR levels. In contrast to the ABR's impact on DPOAE response, ABR thresholds were not altered or reduced when preceded immediately by DPOAE measurements. The molecular alterations underlying the ABR-induced transient reduction of DPOAE remain to be determined. To investigate the potential role of reactive oxygen species in post-ABR DPOAE reduction, transgenic mice over-expressing SOD1, the cytoplasmic enzyme critical for removal of superoxide radicals were subjected to the same auditory testing regimen. Similar to their wild type littermates, the SOD1 transgenic mice also demonstrated post-ABR DPOAE reduction, and thus do not support a role for superoxide radicals in transient reduction of DPOAE. While toxic noise exposure is known to negatively impact OAE, transient decrease in DPOAE levels following standard ABR assay has not been previously described. A practical outcome from this study is a recommendation for reversal of the traditional order for carrying out auditory tests, with the OAE measurements preceding ABR assessment, thus ensuring that the DPOAE response is unaffected.


Assuntos
Potenciais Evocados Auditivos do Tronco Encefálico/fisiologia , Células Ciliadas Auditivas/fisiologia , Emissões Otoacústicas Espontâneas/fisiologia , Animais , Limiar Auditivo , Testes Auditivos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Modelos Animais , Espécies Reativas de Oxigênio/metabolismo , Superóxido Dismutase/genética , Superóxido Dismutase/metabolismo , Superóxido Dismutase-1
10.
J Acoust Soc Am ; 127(2): 970-6, 2010 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-20136219

RESUMO

Neuronal gain adaptation has been proposed as the underlying mechanism leading to the perception of phantom sounds such as Zwicker tones and tinnitus. In this gain-adaptation theory, cochlear compression plays a significant role with weaker compression leading to stronger phantom percepts. The specific aim of this study was to find a link between the strength of neuronal gain adaptation and cochlear compression. Compression was assessed using distortion product otoacoustic emissions (DPOAEs). Gain adaptation is hypothesized to manifest itself in the sensitization observed for the detection of masked tones when preceded by notched noise. Perceptual thresholds for pure tones in notched noise were measured at multiple frequencies following various priming signals. The observed sensitization was larger than expected from the combined effect of the various maskers. However, there was no link between sensitization and compression. Instead, across subjects, stronger sensitization correlated with stronger DPOAEs evoked by low-level primaries. In addition, growth of DPOAEs correlated reliably with perceptual thresholds across frequencies within subjects. Together, the data suggest that short-term dynamic adaptation leading to perceptual sensitization is the result of an active process mediated by the outer hair cells, which are thought to modulate the gain of the cochlear amplifier via efferent feedback.


Assuntos
Percepção Auditiva/fisiologia , Cóclea/fisiologia , Ruído , Emissões Otoacústicas Espontâneas , Estimulação Acústica , Adulto , Limiar Auditivo , Potenciais Evocados , Células Ciliadas Auditivas Externas/fisiologia , Humanos , Pessoa de Meia-Idade , Dinâmica não Linear , Psicoacústica , Adulto Jovem
11.
J Acoust Soc Am ; 124(3): 1613-26, 2008 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-19045653

RESUMO

Distortion product otoacoustic emission (DPOAE) level from normal hearing individuals can vary by as much as 30 dB with small frequency changes (a phenomenon known as DPOAE fine structure). This fine structure is hypothesized to stem from the interaction of components from two different regions of the cochlea (the nonlinear generator region and the reflection component from the DP region). An efficient procedure to separate these two components would improve the clinical and research utility of DPOAE by permitting separate evaluation of different cochlea regions. In this paper, two procedures for evaluating DPOAE fine structure are compared: DPOAE generated by fixed-frequency primaries versus continuously sweeping primaries. The sweep DPOAE data are analyzed with a least squares fit filter. Sweep rates of greater than 8 s per octave permit rapid evaluation of the cochlear fine structure. A higher sweep rate of 2 s per octave provided DPOAE without fine structure. Under these conditions, the longer latency reflection component falls outside the range of the filter. Consequently, DPOAE obtained with sweeping tones can be used either to get more rapid estimates of DPOAE fine structure or to obtain estimates of DPOAE from the generator region uncontaminated by energy from the reflection region.


Assuntos
Percepção Auditiva , Cóclea/fisiologia , Modelos Biológicos , Emissões Otoacústicas Espontâneas , Distorção da Percepção , Estimulação Acústica , Limiar Auditivo , Membrana Basilar/fisiologia , Feminino , Humanos , Análise dos Mínimos Quadrados , Masculino , Tempo de Reação , Fatores de Tempo
12.
Artigo em Inglês | MEDLINE | ID: mdl-17066303

RESUMO

We tested for seasonal plasticity of the peripheral auditory system of three North American members of the Sylvioidea: Carolina chickadees (Poecile carolinensis), tufted titmice (Baeolophus bicolor), and white-breasted nuthatches (Sitta carolinensis). We measured three classes of auditory evoked responses (AER) to tone stimuli: sustained receptor/neural responses to pure-tone condensation waveforms, the frequency-following response (FFR), and the earliest peak of the AER to stimulus onset (tone onset response). Seasonal changes were detected in all classes of AERs in chickadees and nuthatches. Seasonal changes in titmice were restricted to the tone onset response. Interestingly, changes detected in chickadees (and to a lesser extent in titmice) were generally in an opposite direction to changes seen in nuthatches, with chickadees exhibiting greater amplitude AER responses in the spring than in winter, and nuthatches exhibiting greater amplitude AER responses in winter than in spring. In addition, the seasonal differences in the sustained responses tended to be broad-band in the chickadees but restricted to a narrower frequency range in nuthatches. In contrast, seasonal differences in the onset response were over a broader frequency range in titmice than in chickadees and nuthatches. We discuss some possible mechanistic and functional explanations for these seasonal changes.


Assuntos
Potenciais Evocados Auditivos/fisiologia , Estações do Ano , Aves Canoras/fisiologia , Estimulação Acústica , Animais , Feminino , Masculino , Plasticidade Neuronal/fisiologia , Fatores Sexuais
13.
J Acoust Soc Am ; 117(6): 3766-76, 2005 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-16018480

RESUMO

A detailed measurement of distortion product otoacoustic emission (DPOAE) fine structure was used to extract estimates of the two major components believed to contribute to the overall DPOAE level in the ear canal. A fixed-ratio paradigm was used to record DPOAE fine structure from three normal-hearing ears over a range of 400 Hz for 12 different stimulus-frequency ratios between 1.053 and 1.36 and stimulus levels between 45 and 75 dB SPL. Inverse Fourier transforms of the amplitude and phase data were filtered to extract the early component from the generator region of maximum stimulus overlap and the later component reflected from the characteristic frequency region of the DPOAE. After filtering, the data were returned to the frequency domain to evaluate the impact of the stimulus-frequency ratio and stimulus level on the relative levels of the components. Although there were significant differences between data from different ears some consistent patterns could be detected. The component from the overlap region of the stimulus tones exhibits a bandpass shape, with the maximum occurring at a ratio of 1.2. The mean data from the DPOAE characteristic frequency region also exhibits a bandpass shape but is less sharply tuned and exhibits greater variety across ears and stimulus levels. The component from the DPOAE characteristic frequency region is dominant at ratios narrower than approximately 1.1 (the transition varies between ears). The relative levels of the two components are highly variable at ratios greater than 1.3 and highly dependent on the stimulus level. The reflection component is larger at all ratios at the lowest stimulus level tested (45/45 dB SPL). We discuss the factors shaping DPOAE-component behavior and some cursory implications for the choice of stimulus parameters to be used in clinical protocols.


Assuntos
Estimulação Acústica , Percepção Sonora/fisiologia , Emissões Otoacústicas Espontâneas/fisiologia , Espectrografia do Som , Humanos , Modelos Lineares , Computação Matemática , Psicoacústica , Psicofisiologia
14.
J Acoust Soc Am ; 116(2): 1066-80, 2004 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-15376673

RESUMO

Hearing thresholds measured with high-frequency resolution show a quasiperiodic change in level called threshold fine structure (or microstructure). The effect of this fine structure on loudness perception over a range of stimulus levels was investigated in 12 subjects. Three different approaches were used. Individual hearing thresholds and equal loudness contours were measured in eight subjects using loudness-matching paradigms. In addition, the loudness growth of sinusoids was observed at frequencies associated with individual minima or maxima in the hearing threshold from five subjects using a loudness-matching paradigm. At low levels, loudness growth depended on the position of the test- or reference-tone frequency within the threshold fine structure. The slope of loudness growth differs by 0.2 dB/dB when an identical test tone is compared with two different reference tones, i.e., a difference in loudness growth of 2 dB per 10-dB change in stimulus. Finally, loudness growth was measured for the same five subjects using categorical loudness scaling as a direct-scaling technique with no reference tone instead of the loudness-matching procedures. Overall, an influence of hearing-threshold fine structure on loudness perception of sinusoids was observable for stimulus levels up to 40 dB SPL--independent of the procedure used. Possible implications of fine structure for loudness measurements and other psychoacoustic experiments, such as different compression within threshold minima and maxima, are discussed.


Assuntos
Limiar Auditivo/fisiologia , Cóclea/fisiologia , Percepção Sonora/fisiologia , Feminino , Humanos , Masculino , Emissões Otoacústicas Espontâneas , Psicofísica , Processamento de Sinais Assistido por Computador
15.
J Acoust Soc Am ; 112(6): 2882-97, 2002 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-12509010

RESUMO

In recent years, evidence has accumulated in support of a two-source model of distortion product otoacoustic emissions (DPOAEs). According to such models DPOAEs recorded in the ear canal are associated with two separate sources of cochlear origin. It is the interference between the contributions from the two sources that gives rise to the DPOAE fine structure (a pseudoperiodic change in DPOAE level or group delay with frequency). Multiple internal reflections between the base of the cochlea (oval window) and the DP tonotopic place can add additional significant components for certain stimulus conditions and thus modify the DPOAE fine structure. DPOAEs, at frequency increments between 4 and 8 Hz, were recorded at fixed f2/f1 ratios of 1.053, 1.065, 1.08, 1.11, 1.14, 1.18, 1.22, 1.26, 1.30, 1.32, 1.34, and 1.36 from four subjects. The resulting patterns of DPOAE amplitude and group delay (the negative of the slope of phase) revealed several previously unreported patterns in addition to the commonly reported log sine variation with frequency. These observed "exotic" patterns are predicted in computational simulations when multiple internal reflections are included. An inverse FFT algorithm was used to convert DPOAE data from the frequency to the "time" domain. Comparison of data in the time and frequency domains confirmed the occurrence of these "exotic" patterns in conjunction with the presence of multiple internal reflections. Multiple internal reflections were observed more commonly for high primary ratios (f2/f1 > or = 1.3). These results indicate that a full interpretation of the DPOAE level and phase (group delay) must include not only the two generation sources, but also multiple internal reflections.


Assuntos
Cóclea/fisiologia , Emissões Otoacústicas Espontâneas/fisiologia , Estimulação Acústica , Algoritmos , Meato Acústico Externo/fisiologia , Análise de Fourier , Humanos , Janela do Vestíbulo/fisiologia , Psicoacústica , Valores de Referência , Processamento de Sinais Assistido por Computador , Espectrografia do Som
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