Glenis Long | Graduate Center of the City University of New York (original) (raw)

Papers by Glenis Long

The Journal of the Acoustical Society of America, 1994

The normalized cross-correlation function between the amplitude and frequency fluctuations of 11 ... more The normalized cross-correlation function between the amplitude and frequency fluctuations of 11 spontaneous otoacoustic emissions was measured. A significant correlation was found in seven subjects. The correlation coefficient ranged from -0.37 to +0.65 across subjects. In four subjects, the amplitude fluctuation lagged the frequency fluctuation. The time lag was between 1.6 and 5.5 ms. The results were interpreted using a noise-perturbed limit-cycle oscillator with nonlinear (Duffing) stiffness as a model for a spontaneous emission. The data show that the relative increase of the nonlinear stiffness in this model was between -0.010 and +0.015. This indicates that an even-order nonlinear stiffness plays a minor role in the emission generator. 0.5-0.0--0.5--t .0 0 ß ß ß ß ß ß 1 2 Emission frequency (kHz) 0.5' o.o] -0.5 -1.0 0 (b) ß ß ß ß ß ß FIG. 4. (a) Scatterplot of normalized cross-correlation coefficients versus frequency. (b) Scatterplot of the relative increase of oscillator stiffness (parameter b in Sec. I) versus frequency. These estimates are based on the Duffing oscillator model [see Eqs. (20)-(22)].

The Journal of the Acoustical Society of America, 1990

Amplitude and frequency fluctuations of spontaneous otoacoustic emissions have been studied. Spon... more Amplitude and frequency fluctuations of spontaneous otoacoustic emissions have been studied. Spontaneous otoacoustic emissions were recorded from eight human ears and two frog ears (Rana esculenta). Record length typically was 80 s. For a recorded emission signal, the amplitude signal .4 (t) (average.40) and time intervals T(ti) between successive positive-going zero crossings (i counts zero crossings) were determined. Emission amplitude and period both showed small fluctuations: 3.4•,•/.4o ranged from 0.7 X 10 -• to 6.3 X 10-2 for human emissions and was 24 X 10 -2 for both frog emissions; •T•ms ranged from 1.4 to 6.9 X 10 -? s for human emission and was 50.0 and 55.0)< 10-? s for the two frog emissions. There was a positive correlation between •.4•m•/.40 and 3Tr•s as determined for different emissions (R = 0.9). Spectra of A (t) and T( ti ) revealed that amplitude and period were slowly fluctuating functions: cutoff frequency Af• of the amplitude spectrum ranged from 3 to 18 Hz; Afar ranged from 7 to 32 Hz. Results have been compared to amplitude and frequency fluctuations era second-order oscillator, that interacts With a noise source. It has been concluded that an oscillator with linear stiffness (for example a Van der Pol oscillator) driven by white Gaussian noise, cannot account for all experimental results. Other possible oscillators (e.g., nonlinear stiffness) and noise sources (e.g., narrow-band noise), that may account for the observed phenomena, are discussed. PACS numbers: 43.64Jb, 43.64.Bt INTRODUCTION Spontaneous otoacoustic emissions (SOAE) are narrow-band acoustic signals ( Kemp, 1979; Zurek, 1981; Palmer and Wilson, 1981 ). They have been recorded in quantity from human (Dallmayr, 1985; Strickland et al., 1985; Rebillard etaL, 1987) and frog ears (Wilson etaL, 1986; van Dijk et al., 1989). Many hearing researchers consider the existence of SOAEs as important evidence for the hypothesis that the inner ear makes use of active signal filtering, in order to optimize its performance as signal detector (Dallos, 1988). Under certain conditions, an active filter can become unstable, which results in oscillation. Instability of an active filter in the inner ear, would generate a certain amount of acoustical energy, being radiated out into the ear canal (Gold, 1948). Thus, SOAEs are possibly a byproduct of active signal processing in the inner ear.

Animal Sonar Systems, 1980

The Journal of the Acoustical Society of America, 2008

Distortion product otoacoustic emission ͑DPOAE͒ level from normal hearing individuals can vary by... more Distortion product otoacoustic emission ͑DPOAE͒ level from normal hearing individuals can vary by as much as 30 dB with small frequency changes ͑a phenomenon known as DPOAE fine structure͒. 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 region͒. 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.

The Journal of the Acoustical Society of America, 2007

ABSTRACT Stimulus frequency otoacoustic emissions (SFOAE) are generated by single tones. This is ... more ABSTRACT Stimulus frequency otoacoustic emissions (SFOAE) are generated by single tones. This is both an advantage and a disadvantage. The advantage is that they are more likely to be primarily generated from a more limited region of the cochlea than other types of OAE. The disadvantage is that when tone pulses are used, they occur at the same frequency and time as the stimulus, making it very difficult to separate the OAE from the signal, unless one uses suppression. The SFOAE is generated in the cochlea and has to travel along the basilar membrane before being measured in the ear canal. Cochlear travel times mean that the SFOAE is always delayed relative to the stimulus. The delay is frequency dependent. We have modified the continuously sweeping tone procedure developed in our lab for evaluating DPOAE to separate the stimulus and SFOAE. The LSF procedure was modified to permit dynamic fitting of the delay of a given signal component permitting the extraction of the time varying SFOAE.

The Journal of the Acoustical Society of America, 1992

The Journal of the Acoustical Society of America, 1993

The Journal of the Acoustical Society of America, 2011

The Journal of the Acoustical Society of America, 2008

The Journal of the Acoustical Society of America, 2004

Although otoacoustic emissions (OAE) are used as clinical and research tools, the correlation bet... more Although otoacoustic emissions (OAE) are used as clinical and research tools, the correlation between OAE behavioral estimates of hearing status is not large. In normal‐hearing individuals, the level of OAEs can vary as much as 30 dB when the frequency is changed ...

The Journal of the Acoustical Society of America, 1997

Detailed analysis of spontaneous otoacoustic emissions ͑SOAEs͒ in human subjects revealed that al... more Detailed analysis of spontaneous otoacoustic emissions ͑SOAEs͒ in human subjects revealed that all stable SOAEs sufficiently above the noise floor to permit appropriate analysis have sidebands at multiples of approximately 1 Hz. This is consistent with the hypothesis that SOAEs are modulated by heartbeat. Simultaneous measurement of the rate of blood flow to the thumb and the separation of the spectral sidebands demonstrated that they covary ͑rϭ0.982, pϽ5ϫ10 Ϫ10 ͒. An adaptive least-squares fit ͑LSF͒ paradigm was developed to facilitate the measurement of the instantaneous frequency and amplitude of the signals. A combination of traditional spectral analyses and new LSF analyses showed that the sideband generation stems from frequency modulation of the emissions. If there is any amplitude modulation correlated with the blood flow, it is below the noise floor of the analysis. The frequency of the emission was at a minimum when the blood flow was maximal. Examination of alternative mechanisms using computer simulations suggests that these changes stem from changes of 10-100 ppm in the mass of the basilar membrane.

Journal of Comparative Physiology ? A, 1977

Thresholds for pure tones masked by broad band white noise were measured in the bat, Rhinolophus ... more Thresholds for pure tones masked by broad band white noise were measured in the bat, Rhinolophus ferrumequinum, using a classically conditioned response to shock. The critical ratios obtained from the masked thresholds differ from those obtained from other mammals in that some of the fine structure of the behavioural hearing curve is reflected in the critical ratio curve. This difference is discussed in relation to specializations of the auditory system of this bat.

Journal of Comparative Physiology A, 2007

We tested for seasonal plasticity of the peripheral auditory system of three North American membe... more 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 diVerences in the sustained responses tended to be broad-band in the chickadees but restricted to a narrower frequency range in nuthatches. In contrast, seasonal diVerences 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.

Hearing Research, 1984

Factors leading to the microstructure of the audiogram (a constant pattern of threshold maxima an... more Factors leading to the microstructure of the audiogram (a constant pattern of threshold maxima and minima as a function of frequency) are shown to influence masked thresholds, changing the shape of masking functions when both constant and variable tonal maskers are used. Simultaneous masking with broadband noise gradually reduces the difference between threshold maxima and minima until no further differences can be seen when masked thresholds are above 40-50 dB SPL. Nonsimultaneous masking with broadband noise reveals a changed microstructure when thresholds are elevated above 30-40 dB SPL. Thus in both simultaneous and nonsimultaneous masking the rate of threshold growth with increasing masker level is different for tones from threshold minima than for tones from threshold maxima. These psychophysical measures are related to measures of evoked cochlear emissions and the results are discussed in terms of the implications for understanding the cochlear mechanisms responsible for the microstructure and for the interpretation of psychophysical measures with low level stimuli.

Hearing Research, 2012

When hearing thresholds are measured with high-frequency resolution there is a pseudo-periodic va... more When hearing thresholds are measured with high-frequency resolution there is a pseudo-periodic variation in thresholds across frequency of up to 15e20 dB. This variation is called threshold fine structure (previously referred to as threshold microstructure). Consequently, estimates of auditory status based on threshold measures can depend greatly on the specific frequency evaluated. The impact of threshold fine structure on the prediction of auditory status was examined by measuring detection thresholds of pure tones (providing an indication of threshold fine structure) and comparing them with thresholds obtained using linear sweeps, sinusoidally frequency modulated tones, and narrow-band noise. Spontaneous otoacoustic emissions (SOAEs) were also obtained to confirm the established relationship between threshold fine structure and SOAEs. Thresholds obtained using linear sweeps and narrow-band noise provided stable threshold estimates indicating that such threshold estimates were less influenced by threshold fine structure. Consequently, thresholds obtained with these stimuli may provide estimates of cochlear status less dependent of the exact frequency being evaluated, permitting better prediction of performance on other psychoacoustic measures (such as cochlear tuning and loudness perception) and the properties of their more objective measures (such as otoacoustic emissions).

Perception & Psychophysics, 1973

The role of the standard in a fixed-standard experiment of auditory amplitude discrimination was ... more The role of the standard in a fixed-standard experiment of auditory amplitude discrimination was examined by varying the proportion of trials on which it was presented. The results suggest that the Os may use different perceptual strategies, depending on the availability of the standard. While they did better on trials containing a standard regardless of the proportion of such trials, their accuracy on both "standard-present" and "standard-absent" trials was positively related to the probability of the particular type of trial. These results conflict with the claim of advocates of the roving-standard paradigm that the 0 in the fixed-standard experiment does not use the standard but, rather, compares the variable with a long-term referent built up over many trials. The introduction of a second pair of tones, making it a random-standard experiment, produced considerable response bias tied to the stimulus level and to an overall deterioration in performance.

The human auditory system has a remarkable ability to "hear out" a wanted sound (target) in the b... more The human auditory system has a remarkable ability to "hear out" a wanted sound (target) in the background of unwanted sounds. One important property of sound which helps us hear-out the target is inharmonicity. When a single harmonic component of a harmonic complex is slightly mistuned, that component is heard to separate from the rest. At high harmonic numbers, where components are unresolved, the harmonic segregation effect is thought to result from detection of modulation of the time envelope (roughness cue) resulting from the mistuning. Neurophysiological research provides evidence that such envelope modulations are represented early in the auditory system, at the level of the auditory nerve. When the mistuned harmonic is a low harmonic, where components are resolved, the harmonic segregation is attributed to more centrally-located auditory processes, leading harmonic components to form a perceptual group heard separately from the mistuned component. Here we consider an alternative explanation that attributes the harmonic segregation to detection of modulation when both high and low harmonic numbers are mistuned. Specifically, we evaluate the possibility that distortion products in the cochlea generated by the mistuned component introduce detectable beating patterns for both high and low harmonic numbers. Distortion product otoacoustic emissions (DPOAEs) were measured using 3, 7, or 12-tone harmonic complexes with a fundamental frequency (F0) of 200 or 400 Hz. One of two harmonic components was mistuned at each F0: one from resolved harmonics and the other from unresolved harmonics. Many non-harmonic DPOAEs are present whenever a harmonic component is mistuned. These non-harmonic DPOAEs are often separated by the amount of the mistuning (∆F). This small frequency difference will generate a slow beating pattern at ∆F, because this beating is only present when a harmonic component is mistuned, it could provide a cue for behavioral detection of harmonic complex mistuning and may also be associated with the modulation of auditory nerve responses.

HEARING — Physiological Bases and Psychophysics, 1983

The Journal of the Acoustical Society of America, Mar 1, 1991

Many of the aspects of the interaction of spontaneous otoacoustic emissions with external tones (... more Many of the aspects of the interaction of spontaneous otoacoustic emissions with external tones (suppression and synchronization ) can be qualitatively simulated by the behavior of a single driven Van der Pol oscillator. Analytical and numerical investigations of a model of spontaneous otoacoustic emissions based on such an oscillator (with appropriate parametric changes in the nonlinear and negative damping components) lead to predictions of the nature of the changes in suppression and synchronization (frequency-locking) tuning curves when the levels of spontaneous otoacoustie emissions are modified. Observations of the suppression and synchronization of spontaneous otoacoustic emissions by external tones of different frequencies and levels were obtained while the levels of spontaneous emissions were altered by aspirin administration. Modeling an emission as a single Van der Pol oscillator qualitatively accounts for: (1) the reduction of the level of an external tone required to suppress the emission by a decibel amount equivalent to the level reduction induced by aspirin administration; (2) the broadening of the frequency-locking tuning curve of an emission whose level is reduced; and (3) the pulling of the emission frequency by an external tone. It does not account for: ( 1 ) the observed asymmetry in the slopes of the external-tone suppression curves (more gradual for frequencies of the suppressor tone higher, rather than lower, than that of the emission ); and (2) the frequency pushing of the emission by an external tone. PACS numbers: 43.64.Bt, 43.64.Jb INTRODUCTION Approximately 40%-50% of normal-hearing humans generate tonal signals ofcochlear origin even when no acoustic stimuli are delivered to their ears (reviewed in Zurek, 1985). These tonal signals are known as spontaneous otoacoustic emissions. The statistical distribution of sound pressure in the ear canal for some spontaneous emissions has been found to have a minimum at zero pressure (Bialek and Wit, 1984; Wit, 1986; Long etal., 1988), which is characteristic of systems with nonlinear active damping (Bialek and Wit, 1984; Wit, 1986, 1989). Acoustic tonal stimuli applied to the ear interact with a spontaneous otoacoustic emission by suppressing (reducing the amplitude of) the emission, beating with it, or entraining it (forcing it to oscillate at the frequency of the external stimulus). The level of a tone needed to suppress a spontaneous otoacoustic emission by a fixed amount (e.g., 3 dB) is a function of the frequency difference between the external tone and the emission (suppression tuning curve; e.g., Zurek, 1981; Rabinowitz and Widen, 1984). The similarity of suppression tuning curves for spontaneous (and evoked emissions) and the tuning curves ob-Portions of this work were presented in preliminary form at the 116th Meetingof the Acoustical Society of America in Honolulu, Hawaii [ Long eta!., I. Acoust. Soe. Am. Suppl. I 84, S74 (1988)]. Now at Thinking Machines, Inc., Cambridge, MA 02142. tained from measures of the response of the basiliar membrane, hair cells, and VIIIth nerve fibers (reviewed in Patuzzi and Robertson, 1988) suggests that suppression of an emission is related to the mechanical tuning of the basilar membrane. Similarly, the frequency at which an external tone will synchronize a spontaneous emission depends on the level of the external tone (synchronization tuning curve; e.g., Wilson and Sutton, 1981; Zwicker and Schloth, 1984; Long and Tubis, 1988a). A psyehoacoustic equivalent of the synchronization tuning curve is the transition between the perception of a rough or beating stimulus to a tonelike stimulus (Kemp, 1979; Long and Tubis, 1988a). It has been shown previously that nonlinear active oscillators of the Van der Pol type (simple limit-cycle oscillators) can give a qualitative account of: ( 1 ) the statistical properties of spontaneous emission s (Bialek and Wit, 1984; Wit, 1986); (2) the self-interactions of spontaneous emissions (Jonesetal., 1986); (3) the correlated behavior of spontaneous emission levels and psychoacoustic threshold microstructure during aspirin administration (Long and Tubis, 1988b); (4) the beating with, and synchronization of, spontaneous emissions by external tones (Long et al., 1988; Long and Tubis, 1988a; Tubis et aL, 1989}, and (5) the entrainment of spontaneous emissions to cubic difference tones produced in the cochlea by the interaction of two external tones (van Dijk and Wit, 1988). Simulations of spontaneous otoacoustic emissions as Van der Pol oscillators, with appropri-

Evidence has recently been obtained for several interact ions among spontaneous otoacoustic emiss... more Evidence has recently been obtained for several interact ions among spontaneous otoacoustic emissions (SOAEs) including intermodulation distortion products, mutual suppression, and noncontiguous-linked SOAEs which ap parently share energy between two quasi-stable states. In this paper, we give an updated record of our findings on intermodulation distortion products and linked emissions, and give evidence that the former tend to occur when a distortion product frequency is close to that of a cochlear resonance. Computer simulations of the interactions among van der Pol oscillators, which represent nonlinear active elements in a simplified cochlear model, appear to qualitatively account for some of the observed features of SOAE interactions.

The Journal of the Acoustical Society of America, 1994

The normalized cross-correlation function between the amplitude and frequency fluctuations of 11 ... more The normalized cross-correlation function between the amplitude and frequency fluctuations of 11 spontaneous otoacoustic emissions was measured. A significant correlation was found in seven subjects. The correlation coefficient ranged from -0.37 to +0.65 across subjects. In four subjects, the amplitude fluctuation lagged the frequency fluctuation. The time lag was between 1.6 and 5.5 ms. The results were interpreted using a noise-perturbed limit-cycle oscillator with nonlinear (Duffing) stiffness as a model for a spontaneous emission. The data show that the relative increase of the nonlinear stiffness in this model was between -0.010 and +0.015. This indicates that an even-order nonlinear stiffness plays a minor role in the emission generator. 0.5-0.0--0.5--t .0 0 ß ß ß ß ß ß 1 2 Emission frequency (kHz) 0.5' o.o] -0.5 -1.0 0 (b) ß ß ß ß ß ß FIG. 4. (a) Scatterplot of normalized cross-correlation coefficients versus frequency. (b) Scatterplot of the relative increase of oscillator stiffness (parameter b in Sec. I) versus frequency. These estimates are based on the Duffing oscillator model [see Eqs. (20)-(22)].

The Journal of the Acoustical Society of America, 1990

Amplitude and frequency fluctuations of spontaneous otoacoustic emissions have been studied. Spon... more Amplitude and frequency fluctuations of spontaneous otoacoustic emissions have been studied. Spontaneous otoacoustic emissions were recorded from eight human ears and two frog ears (Rana esculenta). Record length typically was 80 s. For a recorded emission signal, the amplitude signal .4 (t) (average.40) and time intervals T(ti) between successive positive-going zero crossings (i counts zero crossings) were determined. Emission amplitude and period both showed small fluctuations: 3.4•,•/.4o ranged from 0.7 X 10 -• to 6.3 X 10-2 for human emissions and was 24 X 10 -2 for both frog emissions; •T•ms ranged from 1.4 to 6.9 X 10 -? s for human emission and was 50.0 and 55.0)< 10-? s for the two frog emissions. There was a positive correlation between •.4•m•/.40 and 3Tr•s as determined for different emissions (R = 0.9). Spectra of A (t) and T( ti ) revealed that amplitude and period were slowly fluctuating functions: cutoff frequency Af• of the amplitude spectrum ranged from 3 to 18 Hz; Afar ranged from 7 to 32 Hz. Results have been compared to amplitude and frequency fluctuations era second-order oscillator, that interacts With a noise source. It has been concluded that an oscillator with linear stiffness (for example a Van der Pol oscillator) driven by white Gaussian noise, cannot account for all experimental results. Other possible oscillators (e.g., nonlinear stiffness) and noise sources (e.g., narrow-band noise), that may account for the observed phenomena, are discussed. PACS numbers: 43.64Jb, 43.64.Bt INTRODUCTION Spontaneous otoacoustic emissions (SOAE) are narrow-band acoustic signals ( Kemp, 1979; Zurek, 1981; Palmer and Wilson, 1981 ). They have been recorded in quantity from human (Dallmayr, 1985; Strickland et al., 1985; Rebillard etaL, 1987) and frog ears (Wilson etaL, 1986; van Dijk et al., 1989). Many hearing researchers consider the existence of SOAEs as important evidence for the hypothesis that the inner ear makes use of active signal filtering, in order to optimize its performance as signal detector (Dallos, 1988). Under certain conditions, an active filter can become unstable, which results in oscillation. Instability of an active filter in the inner ear, would generate a certain amount of acoustical energy, being radiated out into the ear canal (Gold, 1948). Thus, SOAEs are possibly a byproduct of active signal processing in the inner ear.

Animal Sonar Systems, 1980

The Journal of the Acoustical Society of America, 2008

Distortion product otoacoustic emission ͑DPOAE͒ level from normal hearing individuals can vary by... more Distortion product otoacoustic emission ͑DPOAE͒ level from normal hearing individuals can vary by as much as 30 dB with small frequency changes ͑a phenomenon known as DPOAE fine structure͒. 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 region͒. 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.

The Journal of the Acoustical Society of America, 2007

ABSTRACT Stimulus frequency otoacoustic emissions (SFOAE) are generated by single tones. This is ... more ABSTRACT Stimulus frequency otoacoustic emissions (SFOAE) are generated by single tones. This is both an advantage and a disadvantage. The advantage is that they are more likely to be primarily generated from a more limited region of the cochlea than other types of OAE. The disadvantage is that when tone pulses are used, they occur at the same frequency and time as the stimulus, making it very difficult to separate the OAE from the signal, unless one uses suppression. The SFOAE is generated in the cochlea and has to travel along the basilar membrane before being measured in the ear canal. Cochlear travel times mean that the SFOAE is always delayed relative to the stimulus. The delay is frequency dependent. We have modified the continuously sweeping tone procedure developed in our lab for evaluating DPOAE to separate the stimulus and SFOAE. The LSF procedure was modified to permit dynamic fitting of the delay of a given signal component permitting the extraction of the time varying SFOAE.

The Journal of the Acoustical Society of America, 1992

The Journal of the Acoustical Society of America, 1993

The Journal of the Acoustical Society of America, 2011

The Journal of the Acoustical Society of America, 2008

The Journal of the Acoustical Society of America, 2004

Although otoacoustic emissions (OAE) are used as clinical and research tools, the correlation bet... more Although otoacoustic emissions (OAE) are used as clinical and research tools, the correlation between OAE behavioral estimates of hearing status is not large. In normal‐hearing individuals, the level of OAEs can vary as much as 30 dB when the frequency is changed ...

The Journal of the Acoustical Society of America, 1997

Detailed analysis of spontaneous otoacoustic emissions ͑SOAEs͒ in human subjects revealed that al... more Detailed analysis of spontaneous otoacoustic emissions ͑SOAEs͒ in human subjects revealed that all stable SOAEs sufficiently above the noise floor to permit appropriate analysis have sidebands at multiples of approximately 1 Hz. This is consistent with the hypothesis that SOAEs are modulated by heartbeat. Simultaneous measurement of the rate of blood flow to the thumb and the separation of the spectral sidebands demonstrated that they covary ͑rϭ0.982, pϽ5ϫ10 Ϫ10 ͒. An adaptive least-squares fit ͑LSF͒ paradigm was developed to facilitate the measurement of the instantaneous frequency and amplitude of the signals. A combination of traditional spectral analyses and new LSF analyses showed that the sideband generation stems from frequency modulation of the emissions. If there is any amplitude modulation correlated with the blood flow, it is below the noise floor of the analysis. The frequency of the emission was at a minimum when the blood flow was maximal. Examination of alternative mechanisms using computer simulations suggests that these changes stem from changes of 10-100 ppm in the mass of the basilar membrane.

Journal of Comparative Physiology ? A, 1977

Thresholds for pure tones masked by broad band white noise were measured in the bat, Rhinolophus ... more Thresholds for pure tones masked by broad band white noise were measured in the bat, Rhinolophus ferrumequinum, using a classically conditioned response to shock. The critical ratios obtained from the masked thresholds differ from those obtained from other mammals in that some of the fine structure of the behavioural hearing curve is reflected in the critical ratio curve. This difference is discussed in relation to specializations of the auditory system of this bat.

Journal of Comparative Physiology A, 2007

We tested for seasonal plasticity of the peripheral auditory system of three North American membe... more 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 diVerences in the sustained responses tended to be broad-band in the chickadees but restricted to a narrower frequency range in nuthatches. In contrast, seasonal diVerences 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.

Hearing Research, 1984

Factors leading to the microstructure of the audiogram (a constant pattern of threshold maxima an... more Factors leading to the microstructure of the audiogram (a constant pattern of threshold maxima and minima as a function of frequency) are shown to influence masked thresholds, changing the shape of masking functions when both constant and variable tonal maskers are used. Simultaneous masking with broadband noise gradually reduces the difference between threshold maxima and minima until no further differences can be seen when masked thresholds are above 40-50 dB SPL. Nonsimultaneous masking with broadband noise reveals a changed microstructure when thresholds are elevated above 30-40 dB SPL. Thus in both simultaneous and nonsimultaneous masking the rate of threshold growth with increasing masker level is different for tones from threshold minima than for tones from threshold maxima. These psychophysical measures are related to measures of evoked cochlear emissions and the results are discussed in terms of the implications for understanding the cochlear mechanisms responsible for the microstructure and for the interpretation of psychophysical measures with low level stimuli.

Hearing Research, 2012

When hearing thresholds are measured with high-frequency resolution there is a pseudo-periodic va... more When hearing thresholds are measured with high-frequency resolution there is a pseudo-periodic variation in thresholds across frequency of up to 15e20 dB. This variation is called threshold fine structure (previously referred to as threshold microstructure). Consequently, estimates of auditory status based on threshold measures can depend greatly on the specific frequency evaluated. The impact of threshold fine structure on the prediction of auditory status was examined by measuring detection thresholds of pure tones (providing an indication of threshold fine structure) and comparing them with thresholds obtained using linear sweeps, sinusoidally frequency modulated tones, and narrow-band noise. Spontaneous otoacoustic emissions (SOAEs) were also obtained to confirm the established relationship between threshold fine structure and SOAEs. Thresholds obtained using linear sweeps and narrow-band noise provided stable threshold estimates indicating that such threshold estimates were less influenced by threshold fine structure. Consequently, thresholds obtained with these stimuli may provide estimates of cochlear status less dependent of the exact frequency being evaluated, permitting better prediction of performance on other psychoacoustic measures (such as cochlear tuning and loudness perception) and the properties of their more objective measures (such as otoacoustic emissions).

Perception & Psychophysics, 1973

The role of the standard in a fixed-standard experiment of auditory amplitude discrimination was ... more The role of the standard in a fixed-standard experiment of auditory amplitude discrimination was examined by varying the proportion of trials on which it was presented. The results suggest that the Os may use different perceptual strategies, depending on the availability of the standard. While they did better on trials containing a standard regardless of the proportion of such trials, their accuracy on both "standard-present" and "standard-absent" trials was positively related to the probability of the particular type of trial. These results conflict with the claim of advocates of the roving-standard paradigm that the 0 in the fixed-standard experiment does not use the standard but, rather, compares the variable with a long-term referent built up over many trials. The introduction of a second pair of tones, making it a random-standard experiment, produced considerable response bias tied to the stimulus level and to an overall deterioration in performance.

The human auditory system has a remarkable ability to "hear out" a wanted sound (target) in the b... more The human auditory system has a remarkable ability to "hear out" a wanted sound (target) in the background of unwanted sounds. One important property of sound which helps us hear-out the target is inharmonicity. When a single harmonic component of a harmonic complex is slightly mistuned, that component is heard to separate from the rest. At high harmonic numbers, where components are unresolved, the harmonic segregation effect is thought to result from detection of modulation of the time envelope (roughness cue) resulting from the mistuning. Neurophysiological research provides evidence that such envelope modulations are represented early in the auditory system, at the level of the auditory nerve. When the mistuned harmonic is a low harmonic, where components are resolved, the harmonic segregation is attributed to more centrally-located auditory processes, leading harmonic components to form a perceptual group heard separately from the mistuned component. Here we consider an alternative explanation that attributes the harmonic segregation to detection of modulation when both high and low harmonic numbers are mistuned. Specifically, we evaluate the possibility that distortion products in the cochlea generated by the mistuned component introduce detectable beating patterns for both high and low harmonic numbers. Distortion product otoacoustic emissions (DPOAEs) were measured using 3, 7, or 12-tone harmonic complexes with a fundamental frequency (F0) of 200 or 400 Hz. One of two harmonic components was mistuned at each F0: one from resolved harmonics and the other from unresolved harmonics. Many non-harmonic DPOAEs are present whenever a harmonic component is mistuned. These non-harmonic DPOAEs are often separated by the amount of the mistuning (∆F). This small frequency difference will generate a slow beating pattern at ∆F, because this beating is only present when a harmonic component is mistuned, it could provide a cue for behavioral detection of harmonic complex mistuning and may also be associated with the modulation of auditory nerve responses.

HEARING — Physiological Bases and Psychophysics, 1983

The Journal of the Acoustical Society of America, Mar 1, 1991

Many of the aspects of the interaction of spontaneous otoacoustic emissions with external tones (... more Many of the aspects of the interaction of spontaneous otoacoustic emissions with external tones (suppression and synchronization ) can be qualitatively simulated by the behavior of a single driven Van der Pol oscillator. Analytical and numerical investigations of a model of spontaneous otoacoustic emissions based on such an oscillator (with appropriate parametric changes in the nonlinear and negative damping components) lead to predictions of the nature of the changes in suppression and synchronization (frequency-locking) tuning curves when the levels of spontaneous otoacoustie emissions are modified. Observations of the suppression and synchronization of spontaneous otoacoustic emissions by external tones of different frequencies and levels were obtained while the levels of spontaneous emissions were altered by aspirin administration. Modeling an emission as a single Van der Pol oscillator qualitatively accounts for: (1) the reduction of the level of an external tone required to suppress the emission by a decibel amount equivalent to the level reduction induced by aspirin administration; (2) the broadening of the frequency-locking tuning curve of an emission whose level is reduced; and (3) the pulling of the emission frequency by an external tone. It does not account for: ( 1 ) the observed asymmetry in the slopes of the external-tone suppression curves (more gradual for frequencies of the suppressor tone higher, rather than lower, than that of the emission ); and (2) the frequency pushing of the emission by an external tone. PACS numbers: 43.64.Bt, 43.64.Jb INTRODUCTION Approximately 40%-50% of normal-hearing humans generate tonal signals ofcochlear origin even when no acoustic stimuli are delivered to their ears (reviewed in Zurek, 1985). These tonal signals are known as spontaneous otoacoustic emissions. The statistical distribution of sound pressure in the ear canal for some spontaneous emissions has been found to have a minimum at zero pressure (Bialek and Wit, 1984; Wit, 1986; Long etal., 1988), which is characteristic of systems with nonlinear active damping (Bialek and Wit, 1984; Wit, 1986, 1989). Acoustic tonal stimuli applied to the ear interact with a spontaneous otoacoustic emission by suppressing (reducing the amplitude of) the emission, beating with it, or entraining it (forcing it to oscillate at the frequency of the external stimulus). The level of a tone needed to suppress a spontaneous otoacoustic emission by a fixed amount (e.g., 3 dB) is a function of the frequency difference between the external tone and the emission (suppression tuning curve; e.g., Zurek, 1981; Rabinowitz and Widen, 1984). The similarity of suppression tuning curves for spontaneous (and evoked emissions) and the tuning curves ob-Portions of this work were presented in preliminary form at the 116th Meetingof the Acoustical Society of America in Honolulu, Hawaii [ Long eta!., I. Acoust. Soe. Am. Suppl. I 84, S74 (1988)]. Now at Thinking Machines, Inc., Cambridge, MA 02142. tained from measures of the response of the basiliar membrane, hair cells, and VIIIth nerve fibers (reviewed in Patuzzi and Robertson, 1988) suggests that suppression of an emission is related to the mechanical tuning of the basilar membrane. Similarly, the frequency at which an external tone will synchronize a spontaneous emission depends on the level of the external tone (synchronization tuning curve; e.g., Wilson and Sutton, 1981; Zwicker and Schloth, 1984; Long and Tubis, 1988a). A psyehoacoustic equivalent of the synchronization tuning curve is the transition between the perception of a rough or beating stimulus to a tonelike stimulus (Kemp, 1979; Long and Tubis, 1988a). It has been shown previously that nonlinear active oscillators of the Van der Pol type (simple limit-cycle oscillators) can give a qualitative account of: ( 1 ) the statistical properties of spontaneous emission s (Bialek and Wit, 1984; Wit, 1986); (2) the self-interactions of spontaneous emissions (Jonesetal., 1986); (3) the correlated behavior of spontaneous emission levels and psychoacoustic threshold microstructure during aspirin administration (Long and Tubis, 1988b); (4) the beating with, and synchronization of, spontaneous emissions by external tones (Long et al., 1988; Long and Tubis, 1988a; Tubis et aL, 1989}, and (5) the entrainment of spontaneous emissions to cubic difference tones produced in the cochlea by the interaction of two external tones (van Dijk and Wit, 1988). Simulations of spontaneous otoacoustic emissions as Van der Pol oscillators, with appropri-

Evidence has recently been obtained for several interact ions among spontaneous otoacoustic emiss... more Evidence has recently been obtained for several interact ions among spontaneous otoacoustic emissions (SOAEs) including intermodulation distortion products, mutual suppression, and noncontiguous-linked SOAEs which ap parently share energy between two quasi-stable states. In this paper, we give an updated record of our findings on intermodulation distortion products and linked emissions, and give evidence that the former tend to occur when a distortion product frequency is close to that of a cochlear resonance. Computer simulations of the interactions among van der Pol oscillators, which represent nonlinear active elements in a simplified cochlear model, appear to qualitatively account for some of the observed features of SOAE interactions.