摘要:

Otoreflectance refers to acoustic pressure reflectance measurements in the ear canal, by the use of a leak-free insertion of a probe assembly, in the frequency or time domain over a range of two or more stimulus levels. Otoreflectance includes an iso-level response indicative of the forward transfer of acoustic energy into the middle ear, and nonlinear responses indicative of the acoustic energy reflected back from the cochlea. The nonlinear otoreflectance decouples the reflected energy in an evoked otoacoustic emission (OAE) from its subsequent re-reflected energy due to the presence of the ear-canal probe. Nonlinear otoreflectance responses are extremely sensitive to probe distortion, and a double-evoked (2E) technique, previously used in evoked (OAE) measurements, is adapted for otoreflectance to solve the distortion problem. Results are obtained using a 2E stimulus set containing a set of three click stimuli delivered through a pair of sources. The corresponding sets of three pressure responses are acquired in a calibration tube, and in the ear canal, and a set of three iso-level ear-canal reflectances is calculated. An evoked OAE can be decomposed into a otoacoustic reflected pressure (ORP), and a nonlinear otoreflectance is defined by the ratio of the ORP to the initial pressure spectrum. Otoreflectance provides simultaneous measurements of middle-ear and cochlear responses, and has potential, as yet untested, for application to clinical tests for hearing impairments.

ISSN:0001-4966    

DOI:10.1121/1.420340

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Since Kemp [J. Acoust. Soc. Am.64, 1386–1391 (1978)] first described click-evoked otoacoustic emissions (COAEs), researchers have advocated their use as an excellent tool for diagnosing hearing loss in infants and children. However, there are few detailed reports of COAEs in this population, and those that do exist suggest that there are age-dependent differences. The purpose of the current study was to determine basic characteristics of COAEs in infants, toddlers, children, and young adults and to define any differences among age groups. An additional goal was to ensure that spontaneous otoacoustic emissions (SOAEs) did not confound any possible developmental effects. COAEs and SOAEs were measured from one ear of 223 normal-hearing subjects. COAE input/output functions indicated that children aged less than one year have higher COAE levels than older children and adults. Children aged 1–5 yr had higher COAE levels than those aged 12–17 yr and adults. These differences were independent of level and SOAE status, but were dependent on frequency. The results of this study suggest that different clinical norms may be necessary for children aged less than 6 years.

ISSN:0001-4966    

DOI:10.1121/1.420341

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Distortion-product otoacoustic emissions at the2 f1−f2frequency (DPOAEs) are being advocated as a clinical tool for diagnosis of peripheral auditory pathology. Because they can be measured quickly and noninvasively, they may be an excellent method for identifying hearing loss in infants and children. However, few studies have examined the characteristics of DPOAEs in infants and children or detailed if, and how, their responses differ from those of adults. The purpose of the current study was to determine basic characteristics of DPOAEs in infants, toddlers, children, and young adults and to define any differences among age groups. An additional goal was to ensure that the presence of spontaneous otoacoustic emissions (SOAEs) did not confound any developmental effect. DPOAE input/output (I/O) functions at sevenf2frequencies and SOAEs were measured from one ear of 196 subjects. Children aged less than 1 yr had significantly higher mean DPOAE levels than older children and adults, and children aged 1–3 yr had higher mean DPOAE levels than teens and adults. These differences were dependent on frequency but were independent off2level and SOAE status. At everyf2frequency, groups of individuals having SOAEs had higher mean DPOAE levels than those not having SOAEs.

ISSN:0001-4966    

DOI:10.1121/1.420342

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Amplitudes of odd order distortion products (DPs) that are detected in animal ear canals have been used to probe cochlear health, to search for cochlear amplification, and to measure aspects of cochlear mechanical frequency response. Like the DP amplitude, DP phase is also an important measure of the cochlear mechanical response. Reported here are measurements of DP phase in the ear canal of the cat. The phase data show frequency-dependent time delays. One of these delays is a function off2,the frequency of the higher-frequency primary. Hence the DP phaseφdis of the formφd=φ0+ωdτ,whereωdis the DP angular frequency and τ is a fixed time delay. Our results show thatφdis independent of input levela2as long as the ratioa2/a1⩽2,wherea2anda1are the amplitudes of the input tones. Asa2/a1becomes greater than two, the fixed time delays increase for DPs whose frequencies are less than the frequencies of the input tones. When both levels are varied together the delay increases as the levels decrease. There can be phase changes as large as π associated with deep nulls in the DP magnitude for the two lower-frequency DPs. Features of the nulls may be modeled assuming that there is partial reflection of the DP wave from the DP place. The assumption of energy reemitted from the DP place also explains amplitude-ratio-dependent time delays and 2π level-dependent bifurcations in phase. The DP phase shows different dependencies forf22 kHz.

ISSN:0001-4966    

DOI:10.1121/1.420343

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

This paper presents a quantitative model for describing data from modulation-detection and modulation-masking experiments, which extends the model of the “effective” signal processing of the auditory system described in Dau et al. [J. Acoust. Soc. Am.99, 3615–3622 (1996)]. The new element in the present model is a modulation filterbank, which exhibits two domains with different scaling. In the range 0–10 Hz, the modulation filters have a constant bandwidth of 5 Hz. Between 10 Hz and 1000 Hz a logarithmic scaling with a constantQvalue of 2 was assumed. To preclude spectral effects in temporal processing, measurements and corresponding simulations were performed with stochastic narrow-band noise carriers at a high center frequency (5 kHz). For conditions in which the modulation rate(fmod)was smaller than half the bandwidth of the carrier(Δf),the model accounts for the low-pass characteristic in the threshold functions [e.g., Viemeister, J. Acoust. Soc. Am.66, 1364–1380 (1979)]. In conditions withfmod>Δf/2,the model can account for the high-pass characteristic in the threshold function. In a further experiment, a classical masking paradigm for investigating frequency selectivity was adopted and translated to the modulation-frequency domain. Masked thresholds for sinusoidal test modulation in the presence of a competing modulation masker were measured and simulated as a function of the test modulation rate. In all cases, the model describes the experimental data to within a few dB. It is proposed that the typical low-pass characteristic of the temporal modulation transfer function observed with wide-band noise carriers is not due to “sluggishness” in the auditory system, but can instead be understood in terms of the interaction between modulation filters and the inherent fluctuations in the carrier.

ISSN:0001-4966    

DOI:10.1121/1.420344

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

A multi-channel model, describing the effects of spectral and temporal integration in amplitude-modulation detection for a stochastic noise carrier, is proposed and validated. The model is based on the modulation filterbank concept which was established in the accompanying paper [Dau et al., J. Acoust. Soc. Am.102, 2892–2905 (1997)] for modulation perception in narrow-band conditions (single-channel model). To integrate information across frequency, the detection process of the model linearly combines the channel outputs. To integrate information across time, a kind of “multiple-look” strategy, is realized within the detection stage of the model. Both data from the literature and new data are used to validate the model. The model predictions agree with the results of Eddins [J. Acoust. Soc. Am.93, 470–479 (1993)] that the “time constants” associated with the temporal modulation transfer functions (TMTF) derived for narrow-band stimuli do not vary with carrier frequency region and that they decrease monotonically with increasing stimulus bandwidth. The model is able to predict masking patterns in the modulation-frequency domain, as observed experimentally by Houtgast [J. Acoust. Soc. Am.85, 1676–1680 (1989)]. The model also accounts for the finding by Sheft and Yost [J. Acoust. Soc. Am.88, 796–805 (1990)] that the long “effective” integration time constants derived from the data are two orders of magnitude larger than the time constants derived from the cutoff frequency of the TMTF. Finally, the temporal-summation properties of the model allow the prediction of data in a specific temporal paradigm used earlier by Viemeister and Wakefield [J. Acoust. Soc. Am.90, 858–865 (1991)]. The combination of the modulation filterbank concept and the optimal decision algorithm proposed here appears to present a powerful strategy for describing modulation-detection phenomena in narrow-band and broadband conditions.

ISSN:0001-4966    

DOI:10.1121/1.420345

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

The study investigated the ability to detect and discriminate frequency glides under a variety of experimental conditions. The subjects distinguished between a comparison signal that either was level in frequency or was swept across a fixed frequency span, and a target signal that changed more in frequency than the comparison signal. Tone durations were 50 and 400 ms. Nominal center frequencies were 0.5, 2, and 6 kHz; actual center frequencies were varied randomly, or roved, over a range equal to 0.1 times the nominal center frequency. Up- and down-glides were used. The transition span of the comparison signal was either 0, 0.5, 1, or 2 times the equivalent rectangular bandwidth of the auditory filter at the nominal center frequency. Discrimination thresholds were obtained for all combinations of center frequency, direction, and span. Overall, thresholds expressed as ΔHz/ERB varied little as a function of center frequency. Glide duration had no effect on discrimination. The 50-ms down-glides were more difficult to detect than the 50-ms up-glides; otherwise, the effect of direction was not significant. With the exception of the 50-ms down-glides, detection/discrimination thresholds were similar for the 0-, 0.5-, and 1-ERB transition spans, but increased significantly for the 2-ERB span. The absence of significant variation across frequency supports a place mechanism for the detection of frequency change in gliding tones, based on the detection of changes in the excitation pattern. An excitation pattern model cannot account for the asymmetry noted for glide detection, however.

ISSN:0001-4966    

DOI:10.1121/1.420346

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Traditional loudness models have been based on the average energy and the critical band analysis of steady-state sounds. However, most environmental sounds, including speech, are dynamic stimuli, in which the average level [e.g., the root-mean-square (rms) level] does not account for the large temporal fluctuations. The question addressed here was whether two stimuli of the same rms level but different peak levels would produce an equal loudness sensation. A modern adaptive procedure was used to replicate two classic experiments demonstrating that the sensation of “beats” in a two- or three-tone complex resulted in a louder sensation [E. Zwicker and H. Fastl,Psychoacoustics—Facts and Models(Springer-Verlag, Berlin, 1990)]. Two additional experiments were conducted to study exclusively the effects of the temporal envelope on the loudness sensation of dynamic stimuli. Loudness balance was performed by normal-hearing listeners between a white noise and a sinusoidally amplitude-modulated noise in one experiment, and by cochlear implant listeners between two harmonic stimuli of the same magnitude spectra, but different phase spectra, in the other experiment. The results from both experiments showed that, for two stimuli of the same rms level, the stimulus with greater temporal fluctuations sometimes produced a significantly louder sensation, depending on the temporal frequency and overall stimulus level. In normal-hearing listeners, the louder sensation was produced for the amplitude-modulated stimuli with modulation frequencies lower than 400 Hz, and gradually disappeared above 400 Hz, resulting in a low-pass filtering characteristic which bore some similarity to the temporal modulation transfer function. The extent to which loudness was greater was a nonmonotonic function of level in acoustic hearing and a monotonically increasingly function in electric hearing. These results suggest that the loudness sensation of a dynamic stimulus is not limited to a 100-ms temporal integration process, and may be determined jointly by a compression process in the cochlea and an expansion process in the brain. A level-dependent compression scheme that may better restore normal loudness of dynamic stimuli in hearing aids and cochlear implants is proposed.

ISSN:0001-4966    

DOI:10.1121/1.420347

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

This work extends previous studies on the perceptual asymmetry between the local maxima and minima of wide frequency modulations (FMs) [L. Demany and K. I. McAnally, J. Acoust. Soc. Am.96, 706–715 (1994); L. Demany and S. Clément, J. Acoust. Soc. Am.97, 2454–2459 (1995); L. Demany and S. Clément, J. Acoust. Soc. Am.98, 2515–2523 (1995)]. In experiment 1, subjects had to discriminate frequency shifts in the temporally central vertex of V- and Λ-shaped FMs imposed on 200-ms sinusoidal tone bursts. The precise shapes of these FMs varied in eight steps from quasi-triangles (with a durationless central vertex) to quasi-squares (with a long-duration central vertex). The central vertex was either a minimum or a maximum, but in each case the corresponding frequency was near 1000 Hz and the FM span was about 0.5 oct. For each FM shape, the discrimination threshold was lower when the vertex was a maximum than when it was a minimum, but (in four subjects out of five) this difference decreased monotonically as the FM became less and less triangular. FM shape had a remarkably small effect on the discrimination of the maxima, and the thresholds measured for the sharpest maxima were unexpectedly low. In subsequent experiments, subjects had to discriminate frequency shifts in the starting point or the final point of unidirectional FMs (tone glides) that spanned about 0.5 oct in 100 ms. The relevant frequency extremum was near 1000 Hz in each condition. At the final point of the glides, discrimination was better for rising glides than for falling glides. At the starting point of the glides, discrimination was better for falling glides than for rising glides. Thus discrimination was always better when the relevant frequency extremum was a maximum than when it was a minimum, and this effect was produced both “forward” and “backward.” The latter fact suggests that the perceptual asymmetry of FM originates at least partly from central factors.

ISSN:0001-4966    

DOI:10.1121/1.420348

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

A study was conducted to determine whether newborn infants organize auditory streams in a manner similar to that of adults. A series of three experiments investigated the ability of 3- to 4-day-old infants to discriminate repeated rising and falling four-tone sequences in two configurations of source timbre and spatial position. It was hypothesized that if the sequences were organized into two auditory streams on the basis of timbre and spatial position, one of the configurations should be discriminable from its reversal while the other should not. The sequences were tested with different pitch and temporal intervals separating the tones. Sequences were discriminated for the first configuration by adults at both fast tempo/small interval and slow tempo/large interval combinations, while only the latter was discriminated by newborns as measured with a non-nutritive high-amplitude sucking paradigm. Neither adults nor infants could discriminate the sequence reversals for the second configuration. The results suggest that newborn infants organize auditory streams on the basis of source timbre and/or spatial position. They also suggest that newborns have limits in temporal and/or pitch resolution when discriminating tone sequences.

ISSN:0001-4966    

DOI:10.1121/1.420349

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP