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The sounds of music play with many perceptual dimensions. We devised a set of psychophysical procedures to better understand how recipients of cochlear implants perceive basic sound attributes involved in music listening.
Two profoundly hard-of-hearing and deaf patients were examined by non-invasive extracranial magnetic stimulation (EMS) in an effort to determine whether EMS could evoke auditory sensations. The patients were fitted with standard earplugs and were stimulated at the auricle, the mastoid and the temporal lobe area. The threshold of auditory sensation (TAS) was determined at each stimulus position and found to be approximately 20-40% of the maximum EMS level (2.0 Tesla). The TAS was generally lowest in mastoid stimulation, but was variable, and dependent on the angle and position of the stimulating coil relative to the skull. Middle-ear muscle reflex (MEMR) tests performed by EMS of the auricle, mastoid and temporal lobe area contralateral to the probe ear were negative. It was concluded that EMS of the auditory system, particularly the mastoid area, can evoke auditory sensations in cochlea-deaf ears, and that this technique deserves further study as a non-invasive procedure for evaluating potential cochlear implant patients in conjunction with electrostimulation.
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.
Internal circuit noise in hearing aids is distracting to a listener and, if loud enough, may interfere with intelligibility, either by direct masking of weak components of speech or through the generation of undesired intermodulation products, which can also act as a source of masking. The objective characteristics of noise may be measured; however, wearers of hearing aids often differ in their subjective reporting of the perceived characteristics of the internal noise. This study reports on the results for four listeners with normal hearing of matching pitch and amplitude to the internal noise generated within a series of hearing aids. Results of these experiments showed that the listeners (a) primarily matched the perceived pitch of the noise to the frequency of their most sensitive hearing, and (b) matched the perceived level of the noise approximately to the total SPL noise level.
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A method was developed to record sterotactically from the cat Superior Olivary Complex (SOC) using glass micropipettes. Sound stimulation was given through a closed system that permitted independent variation of interaural time (delta time) and intensity (delta int) differences. The most common binaural units found (n = 34) were ipsilateral excitatory, contralateral inhibitory (EI1), cells of the Lateral Superior Olive (LSO). Some Medial Superior Olive (MSO) cells and presumed MSO ascending afferents were found but, as noted by other authors, we found it difficult to obtain single unit recordings from this nucleus. The LSO EI cells were mostly sensitive to higher frequencies and showed Peristimulus Time Histograms (PSTHs) consisting of a sharp "On" response followed by a plateau when stimulated with Best Frequency (BF) tone bursts or noise bursts. This "On" response was sensitive to delta time and delta int such that ipsilateral time lead or intensity increase resulted in a stronger response. The response reached a minimum around zero delta time or delta int. No sharp peaks or dips were seen in the physiological range needed for localization, instead the response increased with increasing ipsilateral lead or intensity to the maximum values tested (2048 microseconds delta time, 30 dB delta int). In the physiological range the delta time and delta int response were complementary (both increasing response as ipsilaterality was increased). Provided enough sound energy in the unit's sensitive region was present, the same delta time curves were produced when BF tone bursts, masked tone bursts, "sharp onset" tone bursts or noise bursts were used. Changing the delta time of the carrier of the tone burst alone had no effect (except for one cell with a BF of 560 Hz), only the relative time of arrival of the stimulus envelope seemed to be important. In contrast to these LSO EI cells MSO-type units showed EI or EE predominantly low frequency phase-locked responses. When stimulated with interaurally phase shifted (delta pha) BF tones the unit response was a cyclic function of delta pha. Some cells (all that were tested, n = 6 including the 560 Hz LSO EI cell) showed these cyclic responses when stimulated with noise bursts or non-BF tones. However, these "characteristic delays" were not necessarily in the physiological range, i.e. we could find no evidence that these units were responding to delta time/delta pha values corresponding to a particular sound source direction.(ABSTRACT TRUNCATED AT 400 WORDS)
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.
This study examined the relation of brain stem auditory evoked potentials (BAEPs) for monaural and binaural click stimuli. Responses were recorded from normal subjects for 4 stimulus levels of 50, 70, 90 and 110 dB peSPL peak-to-peak, corresponding to monaural sensation levels of 7, 27, 47 and 67 dB SL. Wave amplitude and latency values were analyzed for the effects of the binaural stimulus condition. Responses to binaural stimuli were compared to the summed responses to monaural stimuli to estimate binaural interactions. The results show that responses to a binaural stimulus have significantly greater wave amplitudes than responses to a monaural stimulus. If a response to a binaural stimulus is compared to the sum of the responses to the corresponding monaural stimuli, however, there are no significant differences in wave V amplitudes. Latency values are equal for the two stimulus conditions. Calculations of a continuous wave form representing the difference (point-by-point) between the response to a binaural stimulus and the summed response to the two monaural stimuli shows that significant binaural interactions occur with a latency of 7-10 msec. Additional interactions occur with a latency of 12-16 msec. Although neural and sonomotor sources may contribute to these short latency binaural interactions, acoustic cross-talk appears to account for a significant portion of the observed interaction.
Seventy-two healthy volunteers aged 24-75 years were submitted to different auditory "oddball" ERP (Event Related Potential) paradigms which included an intensity discrimination and a right/left discrimination task. In both conditions, a late positive component (P3) of the vertex potential appeared. However its latency was about 30 msec greater and its amplitude was smaller in the intensity discrimination paradigm. Moreover, P3 latency increased with age in a strictly linear fashion in the intensity discrimination paradigm, whereas in the right/left discrimination paradigm an increase of latency with age was confined to the older age-groups, which is expressed by a quadratic latency/age function. A relation was found between the subjective feeling of difficulty in performing the tasks and P3 latency in the different paradigms.
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.
The role of pinnae-based spectral cues was investigated by requiring listeners to locate sound, binaurally, in the horizontal plane with and without partial occlusion of their external ears. The main finding was that the high frequencies were necessary for optimal performance. When the stimulus contained the higher audio frequencies, e.g., broadband and 4.0-kHz high-pass noise, localization accuracy was significantly superior to that recorded for stimuli consisting only of the lower frequencies (4.0- and 1.0-kHz low-pass noise). This finding was attributed to the influence of the spectral cues furnished by the pinnae, for when the stimulus composition included high frequencies, pinnae occlusion resulted in a marked decline in localization accuracy. Numerous front-rear reversals occurred. Moreover, the ability to distinguish among sounds originating within the same quadrant also suffered. Performance proficiency for the low-pass stimuli was not further degraded under conditions of pinnae occlusion. In locating the 4.0-kHz high-pass noise when both, neither, or only one ear was occluded, the data demonstrated unequivocally that the pinna-based cues of the "near" ear contributed powerfully toward localization accuracy.
The effects of simultaneous pure-tone maskers on ABR wave V latency and amplitude were examined in three-month-old infants as a means of delineating the frequency specificity of these responses in the immature auditory system. Masking profiles at two intensities (60 and 40 dBn HL) were obtained for click, as well as 4000- and 1000-Hz filtered-click stimuli. Infant profiles, obtained by measuring both latency and amplitude shifts as a result of the discrete-frequency maskers, were compared to adult data obtained under an identical masking paradigm. Both latency and amplitude analyses showed masking profiles for infants which reveal greater low-frequency contribution to responses than found in adult profiles. Additionally, the infant profiles reveal clear differences in the degree of high-frequency spread of masking when comparisons are made to the adult data.
Eight computer models of auditory inner hair cells have been evaluated. From an extensive literature on mammalian species, a subset of well-reported auditory-nerve properties in response to tone-burst stimuli were selected and tested for in the models. This subset included tests for: (a) rate-level functions for onset and steady-state responses; (b) two-component adaptation; (c) recovery of spontaneous activity; (d) physiological forward masking; (e) additivity; and (f) frequency-limited phase locking. As models of hair-cell functioning are increasingly used as the front end of speech-recognition devices, the computational efficiency of each model was also considered. The evaluation shows that no single model completely replicates the subset of tests. Reasons are given for our favoring the Meddis model [R. Meddis, J. Acoust. Soc. Am. 83, 1056-1063 (1988)] both in terms of its good agreement with physiological data and its computational efficiency. It is concluded that this model is well suited to provide the primary input to speech recognition devices and models of central auditory processing.
1. Studies with cats, dogs, and monkeys have shown that bilateral ablation of auditory cortex can result in severe deficits in the ability to localize sounds in space. In the present series of studies we sought to extend this observation to include the laboratory rat. 2. Rats were tested in a two-choice sound-localization task, which required a spatial response to a distant goal box. Although the test conditions were very similar to those employed with cat, dog, and monkey, deficits following cortical ablation were minimal. Indeed, following bilateral ablation of both primary and secondary auditory projection areas, rats were still capable of localization at small angles. 3. Several possibilities were considered to explain the apparent species difference in the effect of cortical ablations. It seemed unlikely that the difference was due simply to testing procedures or details of stimulus presentation. Central nervous system factors were discussed, including the possibility that the degree of impairment was related to the extent of cortical development in different species. It was concluded that the effects of auditory cortical ablation are not the same for all mammals and that for some species auditory cortex is not essential for sound localization.
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Auditory-evoked brain stem potentials were recorded from 12 adults with normal hearing using click stimuli with differences in interaural time and intensity. Almost independent superimposed Jewett V peaks were produced, whose latency and amplitude depended on the parameters of the stimulus applied to either ear. This indicates that separate binaural information for the evaluation of sound source direction is still available at the brain stem level where wave V originates. We demonstrate that the normal nonlinear latency/intensity function may be responsible for the subjective compensation of time and intensity differences, since the well-known trading functions show similar intensity-dependent gradients.
In providing profoundly hearing-impaired persons with processed speech through a signal-processing hearing aid, it is important that the new speech code matches their auditory capacities. This processing capacity for auditory information was investigated in this study. In part 1, the subjects' ability to judge similarities among 8 different but related harmonic complexes was studied. The patterns contained different numbers of harmonics to a 125-Hz fundamental frequency; the harmonics had been spread over the spectrum in various ways. The perceptual judgments appeared to be based on a temporal cue, beat strength, and a spectral cue, related to the balance of high and low frequency components. In part 2, three sets of synthetic vowels were presented to the subjects. Each vowel was realized by summing harmonically related in-phase sinusoids at two formant frequencies. The sets differed in the number of sinusoids per formant: 1, 2 or 3. It was found that the subjects used spectral cues and vowel length for differentiating among the vowels. The overall results show the limited but perhaps usable ability of the profoundly impaired ear to handle spectral information. Implications of these results for the development of signal-processing hearing aids for the profoundly hearing impaired are discussed.
Auditory brainstem responses to monaural clicks and to binaural clicks delivered with interaural time differences of 0.5 and 1 ms (delayed clicks in left ear) and interaural intensity differences (right ear minus left ear) of 0, +/- 10, +/- 20, and +/- 30 dB were recorded bilaterally in 7 normal subjects. Latencies of wave III and wave V were studied as functions of click intensity difference for each of the two time-of-onset differences. As the intensity difference was gradually varied from +30 to -30 dB, the latencies were seen to shift (with constant III--V interval) from those of a monaural right-ear (non-delayed clicks) response to those of a monaural left-ear (delayed clicks) response by 0.5 and 1 ms. In all subjects this shift occurred in the 20-dB interval between equal intensity and 20-dB lagging-click dominance, and almost always most of the shift took place in either of the two 10-dB subintervals. Occasionally double-peaked waves appeared in the 20 dB-interval. Binaural ABRs may become useful for diagnosis in patients with signs of brainstem disorder but with normal-hearing and normal audiometric findings including monaural ABR, as such patients have been found to shift their latencies more slowly with varying interaural intensity difference.