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PubMed2000

Temporal dynamics of pitch strength in regular-interval noises: effect of listening region and an auditory model.

Recently, it was demonstrated that the pitch strength of a stimulus denoted "AABB" differed from rippled noise (RN) despite the fact that their long-term spectra and autocorrelation functions are identical (Wiegrebe et al., 1998). Rippled noise is generated by adding a delayed copy of Gaussian noise back to itself; AABB is generated by concatenating equal-duration, Gaussian-noise segments where every segment is repeated once. It was shown that a simple model based on a two-stage integration process separated by a nonlinear transformation explains the pitch-strength differences quantitatively. Here, we investigate how the spectral listening region influences pitch-strength differences between RN and AABB. Bandpass filtering the two stimuli with a constant bandwidth of 1 kHz revealed a systematic effect of center frequency. For relatively high pitches (corresponding to delays, d, of 4 or 5.6 ms, pitch strength differences between AABB and RN were absent when the pass band was between 0 and 1 kHz. When the pass band was between 3.5 and 4.5 kHz, pitch-strength differences were substantial. For lower pitches (d equal to or longer than 8 ms), AABB had a substantially greater pitch strength independent of the filter center frequency. The model presented in Wiegrebe et al. (1998) cannot capture these effects of center frequency. Here, it is demonstrated that it is possible to simulate the RN-AABB pitch-strength differences, and the effect of listening region, with a computer model of the auditory periphery. It is shown that, in an auditory model, pitch-strength differences are introduced by the nonlinear transformation possibly associated with half-wave rectification or mechanoelectrical transduction. In this experimental context, however, the nonlinearity has perceptual relevance only when the differences in short-term fluctuations of AABB and RN are preserved in auditory-filter outputs. The current experiments relate the purely functional model introduced in the preceding paper to basic properties of the peripheral auditory system. The implication for neural time constants of pitch processing is discussed.

Adult↗
PubMed1979

Auditory discrimination: role of time and intensity in the precedence effect.

Rats were trained to respond on a lever adjacent to a sounding speaker (the sound source) when a single click was emitted. A second click (the artificial echo) was presented through a second speaker on the opposite side. In Condition I, the echo (equal in intensity to the source) was delayed from .015 to 32 milliseconds; greater than 75% correct responses were given for delay times between about .040 milliseconds (lower threshold) and 8 milliseconds (upper threshold). In Condition II, the echo (simultaneous with the source) was reduced in intensity relative to the source over a range from 2.5 decibels to 40 decibels; greater than 75% correct responses occurred for intensity reductions greater than 5 decibels. In Condition III, both the intensity and the delay time of the echo were manipulated in a manner analogous to that which would occur under natural conditions; greater than 95% correct responses were given for delay times from 1 to 32 milliseconds. These data indicate that both time and intensity differences are necessary for localization of primary sources, with delay time contributing more at short echo path distances, and intensity differences at long distances.

Acoustic Stimulation↗
PubMed1984

Frequency-specific auditory brainstem responses to clicks masked by notched noise.

Frequency-specific auditory brainstem responses were recorded as a function of the intensity of a click masked by notch-filtered white noise (i.e. band-stop-filtered). The bandwidth of the notch was fixed at five-thirds octave and the center frequency was 0.5, 1.0, 2.0 or 4.0 kHz. For normally hearing subjects the latency of the main peak in the responses is increasing with decreasing center frequency of the notch and with decreasing click intensity. At a click sensation level of 60 dB, the mean of 7 subjects' peak latency was 6.7 ms for the center frequency 4.0 kHz and 10.2 ms for the center frequency 0.5 kHz. The thresholds derived from the frequency-specific responses were within 20 dB above the subjective thresholds of audibility of the clicks as heard when masked by notched noise.

Adult↗
PubMed1985

Structure and function of the adult inner ear in the mouse following prenatal irradiation.

The function and morphology of the vestibular and cochlear parts of the inner ear have been examined after prenatal irradiation on the 12th, 13th and 16th gestational days in the CBA/CBA mouse. Irradiation was performed with a 0.5, 1 or 2 Gy single dose, whole body irradiation of the pregnant female. The irradiated fetuses were born after full term pregnancies and reached maturity (were 1--2 months old) before inner ears were analyzed with regard to vestibular tests, auditory thresholds and morphology. Morphology was studied by light microscopy (LM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Auditory function was analyzed by frequency specific auditory brainstem response (ABR). Irradiation doses exceeding 2 Gy caused death to the pregnant female, abortion or malformed litters which were eaten by their mothers. Doses of 0.5, 1 and 2 Gy caused malformed cristae ampullares and maculae utriculi, in particular after exposure on the 12th or 13th gestational days. After those doses no abnormality of clinical behaviour of the animals was found. Ultrastructurally, type I hair cells (HC) of the vestibular part seemed more vulnerable to irradiation than the type II HC while the outer (OHC) and inner (IHC) hair cells appeared equally vulnerable. The ultrastructural changes of hair cells were predominantly localized to the hair cell surface showing a defect cuticle which was sometimes malformed and bulging. Sensory hair fusion occurred with a resulting poor maturation of sensory hair rootlets. The efferent nerve endings were estimated to be reduced in number but, if present, they had a normal ultrastructure. Otoconia showed severe morphological damage following irradiation particularly if exposed on the 16th gestational day. Malformed and fused otoconia were frequent having a disarrayed matrix. The irradiation induced morphological alterations in vivo could be reproduced in the in vitro systems. In addition, a retarded growth of the in vitro developing inner ear anlage was estimated to be the same for the vestibular and cochlear parts. The cochlear part of the inner ear showed a dose and age dependent hearing loss following irradiation. A shift of the ABR threshold was recorded in all exposed groups that were irradiated with 2 Gy. A correlation was found between the individual ABR-audiograms and the degree of morphological HC damage in the cochlea along the basilar membrane. The 12th gestational day inner ear anlage was most vulnerable to irradiation. The 13th gestational day inner ear was almost equally vulnerable and showed a dose-response relationship.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Psychophysics of 12 channels implant.

A battery of psychophysic tests has been designed through a computerized command of the patient's emitter. Because of the fatigability of these implanted patients, especially in the case of deaf-mute children, and the tedious aspect of these exams only 4 tests are commonly used: the threshold level in a Békésy way, the tone decay test, the 2 channels discrimination at different intensity levels, the lowest intensity discrimination. If the electrode impedances have been per-operatively measured, these tests are useful to understand the particular phonemic discrimination difficulties of each patient.

Auditory Perception↗
PubMed2001

A new application for the sympathetic skin response: the evaluation of auditory thresholds in cochlear implant patients.

OBJECTIVES: Cochlear implants (CI) are now widely used in patients with profound sensorineural deafness. Determining threshold levels for each CI electrode is required during the initial postoperative tuning session. While behavioral testing is appropriate in post-lingually deafened patients, it may be really tricky in pre-lingually deafened children. CI stimulation is responsible for auditory perception and logically induces brainstem reticular formation arousal which can be studied by sympathetic skin response (SSR). METHODS: Thirteen patients (aged 3-70 years) implanted with an MXM Digisonic((R)) were postoperatively studied. SSR as well as behavioral thresholds were recorded after electrical stimulation of CI electrodes at various intensities. RESULTS: SSR could be recorded in all patients including the 6 studied children. There was a strong correlation between SSR threshold and subjective auditory threshold (r=0.93). CONCLUSIONS: The present data indicate that SSR could have a clinical application as a routine test in postoperative fitting procedures of CIs especially in pre-lingually deafened children.

Adult↗
PubMed2001

Noise enhances modulation sensitivity in cochlear implant listeners: stochastic resonance in a prosthetic sensory system?

Cochlear implants restore auditory sensitivity to the profoundly hearing-impaired by means of electrical stimulation of residual auditory nerve fibers. Sensorineural hearing loss results in a loss of spontaneous activity among the remaining auditory neurons and is accompanied by a reduction in the normal stochastic nature of neural firing in response to electric stimulation. It has been hypothesized that the natural stochasticity of the neural response is important for auditory signal processing and that introducing some optimal amount of noise into the stimulus may improve auditory perception through the implant. In this article we show that, for soft but audible stimuli, an optimal amount of "prosthetic" noise significantly improves sensitivity to envelope modulation in cochlear implant listeners. A nonmonotonic function relates modulation sensitivity and noise level, suggesting the presence of stochastic resonance.

Adult↗
PubMed1999

Using electrically evoked auditory reflex thresholds to fit the CLARION cochlear implant.

This paper describes a method for measuring electrically elicited auditory reflex thresholds (EARTs) in young children who use the CLARION Multi-Strategy Cochlear Implant. The EART is an objective measure that can guide the fitting of a cochlear implant in individuals who are unable to perform behavioral tasks required to program the device. Reflexes were obtained in 11 of 17 pediatric Clarion users. The EART current level indicated a point at which an auditory percept was present and the sound was loud, but not uncomfortable. The EART then was used as a basis for conditioning behavioral responses, and as a guideline for setting most comfortable loudness levels.

Cochlear Implantation↗
PubMed1980

Neurons in the cerebellum of echolocating bats respond to acoustic signals.

Single neurons responding to auditory stimuli (40 msec duration, 0.5 msec rise-decay time) could be isolated from rather large areas of the cerebellar vermis and hemispheres of an echolocating bat, Eptesicus fuscus. These neurons had latencies between 4 and 13 msec and best frequencies between 22 and 77 kHz. The Q10-dB values of their tuning curves were between 1.4 and 16.6. When acoustic stimuli were delivered though the earphones, tuning curves measured from each ear alone were nearly identical in shape and best frequency. The minimum thresholds of these neurons were between 12 and 65 dB SPL. Apparently, these are suitable for reception of the bat's echolocating signals.

Acoustic Stimulation↗
PubMed2002

Temporal resolution of the human primary auditory cortex in gap detection.

The temporal resolution of the primary auditory cortex was studied by recording the magnetic middle latency fields (MAEF) evoked by gaps of 3, 6 and 9 ms inserted in the middle of 600 ms broadband noise bursts. Spatio-temporal source modelling showed that a significant neural representation as reflected by MAEF responses is present at gap durations as low as 3 sms. The comparison of the MAEF waveforms elicited by the onset, gap and offset of the noise bursts indicates that the gap related response near threshold is largely determined by the onset to the burst following the gap. The electro-physiologically derived minimum detectable gap closely resembled the psychoacoustic threshold of 2.0 ms obtained in the same subjects.

Acoustic Stimulation↗
PubMed2006

Clinical evaluation of Parkinson's-related dysphonia.

OBJECTIVES: Nearly one third of patients with idiopathic Parkinson's disease (IPD) cite dysphonia, characterized subjectively as causing a harsh and breathy voice, as their most debilitating deficit. Medical or behavioral treatments may lead to voice improvement. The purpose of this study was 1) to determine whether vocal fold injection of Cymetra (micronized form of collagen, elastin, proteoglycans; Lifecell Co.) is associated with changes in dysphonic voice characteristics in subjects with IPD, as judged perceptually using a standard instrument Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V), and (2) which acoustic and aerodynamic measurements of voice are most reflective of any observed perceptual changes in voice. STUDY DESIGN: Prospective clinical evaluation of patients with Parkinson's-related dysphonia (PRD). METHODS: Six patients with PRD were evaluated before treatment for the presence of dysphonia and glottal gap. All subjects underwent transoral vocal fold collagen injection using topical anesthesia in the otolaryngology clinic as part of their clinical care. At the initial clinic visit, and 10 to14 days after vocal fold collagen injection, patients were asked to complete the Voice Handicap Index (VHI), a questionnaire concerning voice-related quality of life, and perceptual analyses of voice quality were performed. In addition, patients underwent acoustic (pitch/loudness range, maximum phonation time [MPT], and aerodynamic phonation threshold pressure [PTP]) voice analysis. RESULTS: Five of six subjects had self-perceived improvements in voice after treatment, as determined by the VHI (range, +8 to -24). All five subjects who completed testing demonstrated decreased PTP (range, -1.3 to -2.7, P = .002). Five of six subjects demonstrated statistically significant improvements in MPT (range, -2-16 s, P = .05). Five of six subjects had improved pitch range (-26-343 Hz), whereas all subjects had increased intensity range (0.6-23 db) after injection. CONCLUSIONS: Transoral collagen injection in patients with PRD is safe, well tolerated, and is an effective temporary method of subjectively improving voice and speech in selected patients with IPD. Reduction of glottal gap with collagen improves MPT and subglottal PTP. The resulting gain of vocal efficiency may reduce vocal fatigue and provide a useful adjunct to voice therapy for PRD.

Auditory Perception↗
PubMed2005

Spatial unmasking of birdsong in human listeners: energetic and informational factors.

Spatial unmasking describes the improvement in the detection or identification of a target sound afforded by separating it spatially from simultaneous masking sounds. This effect has been studied extensively for speech intelligibility in the presence of interfering sounds. In the current study, listeners identified zebra finch song, which shares many acoustic properties with speech but lacks semantic and linguistic content. Three maskers with the same long-term spectral content but different short-term statistics were used: (1) chorus (combinations of unfamiliar zebra finch songs), (2) song-shaped noise (broadband noise with the average spectrum of chorus), and (3) chorus-modulated noise (song-shaped noise multiplied by the broadband envelope from a chorus masker). The amount of masking and spatial unmasking depended on the masker and there was evidence of release from both energetic and informational masking. Spatial unmasking was greatest for the statistically similar chorus masker. For the two noise maskers, there was less spatial unmasking and it was wholly accounted for by the relative target and masker levels at the acoustically better ear. The results share many features with analogous results using speech targets, suggesting that spatial separation aids in the segregation of complex natural sounds through mechanisms that are not specific to speech.

Acoustic Stimulation↗
PubMed1986

Detection and discrimination of simulated motion of auditory targets in the horizontal plane.

Three experiments investigated subjects' ability to detect and discriminate the simulated horizontal motion of auditory targets in an anechoic environment. "Moving" stimuli were produced by dynamic application of stereophonic balancing algorithms to a two-loudspeaker system with a 30 degree separation. All stimuli were 500-Hz tones. In experiment 1, subjects had to discriminate a left-to-right moving stimulus from a stationary stimulus pulsed for the same duration (300 or 600 ms). For both durations, minimum audible "movement" angles ("MAMA's") were on the order of 5 degrees for stimuli presented at 0 degrees azimuth (straight ahead), and increased to greater than 30 degrees for stimuli presented at +/- 90 degrees azimuth. Experiment 2 further investigated MAMA's at 0 degrees azimuth, employing two different procedures to track threshold: holding stimulus duration constant (at 100-600 ms) while varying velocity; or holding the velocity constant (at 22 degrees-360 degrees/s) while varying duration. Results from the two procedures agreed with each other and with the MAMA's determined by Perrott and Musicant for actually moving sound sources [J. Acoust. Soc. Am. 62, 1463-1466 (1977b)]: As stimulus duration decreased below 100-150 ms, the MAMA's increased sharply from 5 degrees-20 degrees or more, indicating that there is some minimum integration time required for subjects to perform optimally in an auditory spatial resolution task. Experiment 3 determined differential "velocity" thresholds employing simulated reference velocities of 0 degrees-150 degrees/s and stimulus durations of 150-600 ms. As with experiments 1 and 2, the data are more easily summarized by considering angular distance than velocity: For a given "extent of movement" of a reference target, about 4 degrees-10 degrees additional extent is required for threshold discrimination between two "moving" targets, more or less independently of stimulus duration or reference velocity. These data suggest that for the range of simulated velocities employed in these experiments, subjects respond to spatial changes--not velocity per se--when presented with a "motion" detection or discrimination task.

Acoustic Stimulation↗
PubMed1988

Combined monaural and binaural masking release.

Stimulus conditions were examined where both across-frequency [comodulation masking release (CMR)] and across-ear [binaural masking-level difference (BMLD)] cues were available, as well as conditions where only one of these cue types was available. The main goal of the study was to determine how the two types of cues combine. The effects of comodulation were assessed either by modulating a masking noise and manipulating its bandwidth (experiment 1) or by using two comodulated narrow bands of noise separated in frequency (experiment 2). The masker was always No, and the 500-Hz pure-tone signal was either So or S pi. The effect of the frequency of modulation was examined either by changing the frequency of the modulating stimulus (experiment 1) or by changing the bandwidth of the comodulated narrow-band noise (experiment 2). Four of six subjects showed greater masking release when both BMLD and CMR cues were available than for either type of cue alone, whereas the other two subjects did not show an ability to combine the two cues for additional advantage. For the subjects who were able to combine the two types of cue, the additional advantage was greater for low frequencies of modulation. The results indicate that one component of CMR may be based upon across-frequency envelope comparisons at a stage of processing after binaural analysis.

Adolescent↗
PubMed1993

Rate of loudness growth for pure tones in normal and impaired hearing.

The present article provides an analysis of loudness growth rates in normal and cochlear-impaired hearing for diverse groups with respect to age and backgrounds. Slopes are obtained from absolute magnitude estimation and magnitude production of loudness (measured values), and from cross-modality matching and absolute magnitude estimation of apparent length (predicted values). Consistent with an earlier study [R. P. Hellman and C. H. Meiselman, J. Acoust Soc. Am. 88, 2596-2606 (1990)], slopes calculated within the 15-30 dB stimulus range above the elevated threshold increase in size with the degree of hearing loss. The corresponding range of loudness values in normal hearing yields a slope near 0.60 independent of the threshold levels. This pattern of loudness growth holds for individuals and groups. But the intersubject variability of the slope is more labile, being larger across than within groups and larger for the measured slopes than for the predicted values. Determined from the predicted slopes, the coefficient of variation, sigma/m, is approximately constant in normal and impaired hearing ranging from 20%-27%. In contrast, sigma/m, obtained from the measured slopes, increases with the degree of hearing loss to a value of almost 50% for a 75-dB loss. The overall stability and systematics of the observed effects further demonstrate that the loudness-intensity relation can be specified with reasonable precision and accuracy from cross-modality matching.

Acoustic Stimulation↗