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At least 415 records · Page 23Linked to original sources
PubMed1988

Auditory responses to the envelopes of pseudorandom noise stimuli in humans.

Averaged scalp potentials evoked by continuous pseudorandom noise can be cross-correlated with the evoking stimulus, yielding a cross-correlation function (CCF) which reflects neural phase-locking and is quite sensitive for low-frequency stimulus components [M.J. Wilson and R.A. Dobie (1987) Electroencephalogr. Clin. Neurophysiol. 66, 529-538]. However, for higher frequency signals, replicable CCFs can only be obtained at moderate to high intensities. Since auditory neurons also respond to envelopes of complex sounds, even for high-frequency carriers, we compared scalp responses evoked by band-limited complex sounds to the envelopes of these sounds; the resultant envelope cross-correlation functions (ECCFs) contained replicable response components primarily below 1,000 Hz, regardless of the evoking stimulus spectrum. ECCF thresholds for three octave-band stimuli (830-1,562, 1,611-3,125, and 3,174-6,201 Hz) were more sensitive than CCF thresholds (P = 0.006), averaging 35 dB spectrum level for 10 normal subjects. When stimuli with only odd harmonics were used, replicable odd-component scalp responses were seen only in the spectral range of the stimuli, while even-component responses (presumably to stimulus envelope) were seen only in low-passed scalp responses.

Acoustic Stimulation↗
PubMed1989

Spectral characteristics of the responses of primary auditory-nerve fibers to amplitude-modulated signals.

The spectral responses of cat single primary auditory nerve fibers to sinusoidal amplitude-modulated (AM) and double-sideband (DSB) acoustic signals applied to the ear were examined. DSB is an amplitude-modulated signal with a suppressed carrier. Period histograms were compiled from the neural spike-train data, and the frequency spectrum was determined by Fourier transforming these histograms. For DSB signals, spectral components were found to be present at the frequencies of the stimulus as well as at certain combination frequencies. For AM signals, several clusters of spectral components were present. The lowest-frequency cluster consisted of components at DC, at the modulation frequency, and at its harmonics. A higher frequency cluster occurs around a component with the frequency of the carrier. The components of cluster are separated from the carrier by the modulation frequency and its harmonics. Yet higher-frequency clusters appear around multiples of the carrier frequency with components at frequencies separated from these multiples by the modulation frequency and its harmonics. The magnitudes of these spectral components were determined for carrier frequencies located below, at, and above the characteristic frequency of the units, and for different stimulus levels, modulation frequencies, and modulation depths. The low-frequency components present in the neural spike train appear to be the result of demodulation taking place in the inner ear. The demodulated components are strong and are present over a wide range of sound levels, carrier frequencies, modulation frequencies, and nerve-fiber characteristics. This demodulation may be significant for speech recognition.

Acoustic Stimulation↗
PubMed1989

Spectral characteristics of the responses of primary auditory-nerve fibers to frequency-modulated signals.

The spectral responses of cat single primary auditory nerve fibers to sinusoidal frequency-modulated acoustic signals applied to the ear are examined. Period histograms were constructed from the neural spike-train data, and the frequency spectrum was determined by Fourier transforming these histograms. Several clusters of spectral components were present. The lowest-frequency cluster consists of components at DC, at the modulation frequency, and at its harmonics. In the next cluster, components surround the carrier frequency and are separated from it by the modulation frequency and its harmonics. Higher-frequency clusters surround frequencies that are twice and three times the carrier frequency. The components in each cluster are separated from the multiples of the carrier frequency by the modulation frequency and its harmonics. The magnitudes of the spectral components were investigated for carrier frequencies located below, at, and above the unit characteristic frequency, and for different signal levels, modulation frequencies, and modulation indices. The components at the modulation frequency and its harmonics were strong and present over a wide range of signal levels, carrier frequencies, modulation frequencies, and nerve-fiber characteristics. The presence of components at the modulation frequency indicates that a demodulation process is occurring. This process may be significant for speech recognition.

Acoustic Stimulation↗
PubMed1990

Responses of DCN-PVCN neurons and auditory nerve fibers in unanesthetized decerebrate cats to AM and pure tones: analysis with autocorrelation/power-spectrum.

We investigated amplitude-modulated (AM) tone encoding behavior of dorsal and posteroventral cochlear-nucleus (DCN and PVCN) neurons and auditory nerve (AN) fibers in decerebrate unanesthetized cats. Some of the modulation transfer functions (MTFs) were narrowly-tuned band-pass functions; these included responses at moderate and high stimulus levels of DCN pause/build-type-III neurons and the following types of DCN and PVCN chopper neurons: chop-S and/or chop-type-I/III. Other MTFs were broad low-pass or complex functions. Chop-T neurons of the DCN and PVCN tended to exhibit low-pass or flat MTFs. The band-pass MTF neurons exhibited intrinsic oscillations (IOs) in responses to AM or pure tones. The IOs, which were detected in autocorrelation functions and power spectra, were closely correlated (r = 0.863) with the best envelope frequency (BEF). All of the AN fibers showed broad low-pass MTFs with some showing a rudimentary peak in the MTF. The MTFs of DCN-PVCN neurons and AN fibers showed, respectively: (1) BEFs ranging 50-500 Hz, and 400-1300 Hz; (2) upper cut-off frequencies ranging 200-1200 Hz, and 1600-3200 Hz. At stimulus levels of 60-85 dB SPL, maximum modulation gains were as high as 12 dB for DCN-PVCN neurons but were limited to below about 0 dB for AN fibers. The median dynamic ranges of DCN and PVCN neurons (51 and 42 dB, respectively) were substantially wider than those of the low and high spontaneous rate AN fibers (30 and 31 dB, respectively). The observation of higher modulation gain, wider dynamic range, and more narrowly-tuned MTF of DCN-PVCN neurons than AN fibers supports the concept that the capabilities to encode dynamic signals are enhanced in DCN-PVCN neurons compared with AN fibers.

Acoustic Stimulation↗
PubMed1991

On the effect of interaural phase differences on loudness.

The loudness of four monaurally presented Gaussian shaped, 60-ms tone bursts was matched to that of four similar pulses presented binaurally. The stimuli to be matched were all presented in continuous binaural noise of three levels and, in different experiments, either the monaural or the binaural stimuli were adjusted by the observer. With 250- and 710-Hz tone bursts, there are large differences in loudness that, at low signal-to-noise ratios, depend on the interaural phase conditions in a manner consistent with the changes in masked threshold produced by the phase manipulation; there is little, if any, effect of interaural phase on loudness for 2-kHz signals. The effect of interaural phase on loudness decreases with increasing level but, at 250 Hz, remains measurable some 30-40 dB above masked threshold. The matching function for signals out-of-phase grows in proportion to the level to be matched over the entire range from masked threshold to the highest level used. In contrast, for the in-phase condition, the observers show a step at a level that depends both on frequency and on the observer from proportional growth near thresholds to parallel proportional growth some 6 to 12 dB higher.

Acoustic Stimulation↗
PubMed1992

On the relation between the dimensions and resonance characteristics of the vocal tract: a study with MRI.

The relation between the spatial configuration of the vocal tract as determined by magnetic resonance imaging (MRI) and the acoustical signal produced was investigated. A male subject carried out a set of phonatory tasks, comprising the utterance of the sustained vowels /i/ and /a/, each in a single articulation, and the vowel /epsilon/ with his larynx positioned variously on a vertical axis. Two- and three-dimensional measurements of the vocal tract were performed. The results of these measurements were used to calculate resonance frequencies, according to predictions from acoustical theory. Finally, calculated frequencies were compared with actually measured resonance frequencies in the audio signal. We found a strong relation between the acoustical signal produced and the spatial configuration for the first resonance frequencies of the articulations of the vowel /epsilon/, and first two resonance frequencies of the vowels /a/ and /i/. The capability to determine accurately vocal tract dimensions is a major advantage of this imaging technique.

Humans↗
PubMed1992

Temporomandibular joint sounds: correlation to joint structure in fresh autopsy specimens.

In an attempt to better understand the cause of different types of temporomandibular joint (TMJ) sounds, we recorded joint sounds from 27 fresh autopsy specimens, displayed the time frequency distribution of the sound as a three-dimensional graph, and correlated the sound character to morphologic observations at subsequent dissection. Eleven joints elicited sounds, and 16 joints were silent. All joints with sounds had different degrees of intraarticular changes. These ranged from disk displacement with reduction to displacement without reduction and arthrosis of the articular surfaces. Reciprocal clicking occurred both in joints with disk displacement with and without reduction, as well as in joints with arthrotic changes. Crepitation only occurred in joints with arthrosis and perforation. The sample was too small to demonstrate any statistically significant association between the joint sound classified as clicking or crepitation and joint structure types of joint pathosis in this small sample. A high frequency component to the sound appeared to be associated with arthrosis of the articular surfaces. It was concluded that joint sounds indicate joint abnormality but that the absence of joint sound does not exclude intraarticular pathosis.

Aged↗
PubMed1992

Temporomandibular joint sounds and condyle/disk relations on magnetic resonance images.

This study compared the condyle/disk relationships on magnetic resonance images (MRIs) in a group of subjects with completely silent temporomandibular joints (TMJ) when tested clinically with those in subjects with readily discernible TMJ sounds. The sounds were recorded with an accelerometer as the transducer. Selected degrees of jaw separation were electronically determined and recorded with interocclusal wafers for use with the imaging process. Of the "silent joints" 89% were found to have sounds when tested with the accelerometer. These "subclinical" sounds tended to be of shorter duration and occurred at a greater degree of vertical opening than the clinically discernable sounds. The MRIs of the group with clinically discernable sounds tended to show a change in the relationship between the head of the condyle and the intermediate zone of the disk, at the degree of jaw separation of the sound occurrence, whereas no condyle/disk change occurred in the group with "clinically silent joints." It is likely that all joints create sound during function. The different characteristics of the subclinical sounds versus the clinical sounds may indicate differing sound origins.

Adult↗
PubMed2005

Physical determinants of systolic murmur intensity in aortic stenosis.

We investigated which physical parameter has the greatest impact on the perceived loudness of a systolic murmur in aortic stenosis. Loudness of murmur in aortic stenosis correlated best with peak momentum transfer--and thus with body size--so that loud murmurs predict severe disease less reliably in larger patients.

Aged↗
PubMed2005

Usefulness of a new sound spectral averaging technique to distinguish an innocent systolic murmur from that of aortic stenosis.

We present a new method to record and display heart sounds that uses a hand-held computer and stethoscopic recording device. It allows for rapid spectral and waveform displays of murmurs and provides a means for signal averaging of spectral frequency content. Compared with aortic stenosis, innocent murmurs primarily contain frequencies of <300 Hz and persist for a shorter duration at the upper-frequency levels. This method provides for rapid characterization of innocent murmurs, a means for comparison with other murmurs, and transmission of acoustic data to distant sites.

Adolescent↗
PubMed2006

Tracheostomy abolishes paradoxical activation of the vocal cord adductor in multiple system atrophy.

OBJECTIVES: Inspiratory activation of the vocal cord adductor, which causes paradoxical vocal cord motion, develops in patients with multiple system atrophy (MSA). To confirm the hypothesis that airway reflexes trigger such paradoxical activation, we investigated the effects of tracheostomy on the adductor activation in a MSA patient. METHODS: We compared the adductor electromyograms before and after breathing was diverted to a tracheostoma under propofol anesthesia. RESULTS: The adductor inspiratory activation disappeared during tracheostoma breathing. CONCLUSION: Airway reflexes as well as MSA-related damage to the respiratory center contribute to the generation of paradoxical adductor activation in MSA patients.

Electromyography↗
PubMed2004

Variability in fundamental frequency during speech in prodromal and incipient Parkinson's disease: a longitudinal case study.

Nearly two centuries ago, first observed that a particular pattern of speech changes occur in patients with idiopathic Parkinson's disease (PD). Numerous studies have documented these changes using a wide variety of acoustic measures, and yet few studies have attempted to quantify any such changes longitudinally, through the early course of the disease. Moreover, no attempt has been made to determine if speech changes are evident during the prodromal period, prior to the onset of clinically noticeable symptoms. This case-control pilot study is a first attempt to determine if changes in fundamental frequency variability during speech, an acoustic measure known to be affected later in the course of the disease, are evident during the prodromal period. A retrospective analysis of videotape footage recorded and made available by a leading national television news service. Videotape samples were obtained for a single individual (and a well-matched control subject) over an 11-year period of this individual's life (7 years prior to diagnosis of PD, and 3 years post-diagnosis). Results suggest that changes in F0 variability can be detected as early as 5 years prior to diagnosis (consistent with findings from other laboratories that have relied on cross-sectional study approaches). This pilot study supports the utility of such a design approach, and these results warrant continued effort to better understand the onset of PD and sensitivity of measurement of voice acoustical changes during the prodromal period.

Adult↗
PubMed2004

Voice acoustical measurement of the severity of major depression.

A number of empirical studies have documented the relationship between quantifiable and objective acoustical measures of voice and speech, and clinical subjective ratings of severity of Major Depression. To further explore this relationship, speech samples were extracted from videotape recordings of structured interviews made during the administration of the 17-item Hamilton Depression Rating Scale (HDRS; ). Pilot data were obtained from seven subjects (five males, two females) from videotapes that have been used to train expert raters on the administration and scoring of the HDRS. Several speech samples were isolated for each subject and processed to obtain the acoustic measurements. Acoustic measures were selected on the basis that they were correlated with HDRS ratings of symptom severity as seen under ideal voice recording conditions in previous studies. Our findings corroborate earlier reports that speaking rate is well correlated (negatively) with HDRS scores, with a strong correlation and nearly significant trend seen for the measure of pitch variability. A moderate pairwise correlation between percent pause time and HDRS score was also revealed, although this relationship was not statistically significant. The results from this cross-sectional study further demonstrate the ability of voice and speech signal analyses to objectively track severity of depression. In the present case, it is suggested that this relationship is robust enough to be found despite the less than ideal recording conditions and equipment used during the original videotape recording. Voice acoustical analyses may provide a powerful compliment to the standard clinical interview for depression. Use of such measures increases the range of techniques that are available to explore the neurobiological substrates of Major Depression, its treatment, and the dynamic interplay of the systems that govern the motor, cognitive, and emotional aspects of speech production.

Adult↗
PubMed2004

Impaired pitch production and preserved rhythm production in a right brain-damaged patient with amusia.

Pre- and postmorbid singing of a patient with amusia due to a right-hemispheric infarction was analyzed acoustically. This particular patient had a premorbid tape recording of her own singing without accompaniment. Appropriateness of pitch interval and rhythm was evaluated based on ratios of pitch and duration between neighboring notes. The results showed that melodic contours and rhythm were preserved but individual pitch intervals were conspicuously distorted. Our results support a hypothesis that pitch and rhythm are subserved by independent neural subsystems. We concluded that action-related acoustic information for controlling pitch intervals is stored in the right hemisphere.

Auditory Perception↗
PubMed2005

Speech-sound duration processing in a second language is specific to phonetic categories.

The mismatch negativity (MMN) component of the auditory event-related potential was used to determine the effect of native language, Russian, on the processing of speech-sound duration in a second language, Finnish, that uses duration as a cue for phonological distinction. The native-language effect was compared with Finnish vowels that either can or cannot be categorized using the Russian phonological system. The results showed that the duration-change MMN for the Finnish sounds that could be categorized through Russian was reduced in comparison with that for the Finnish sounds having no Russian equivalent. In the Finnish sounds that can be mapped through the Russian phonological system, the facilitation of the duration processing may be inhibited by the native Russian language. However, for the sounds that have no Russian equivalent, new vowel categories independent of the native Russian language have apparently been established, enabling a native-like duration processing of Finnish.

Child↗
PubMed2005

Auditory backward masking deficits in children with reading disabilities.

Studies evaluating temporal auditory processing among individuals with reading and other language deficits have yielded inconsistent findings due to methodological problems () and sample differences. In the current study, seven auditory masking thresholds were measured in fifty-two 7- to 10-year-old children (26 diagnosed with reading disability [RD], 26 without reading disability). Hierarchic multiple regression analyses indicated that RD status predicted performance only in the backward-bandpass noise (p<.05) and backward notched-noise conditions (p<.05), suggesting both temporal and spectral auditory processing deficits. These results suggest that any auditory deficit associated with RD may be more complex than previously hypothesized.

Attention↗
PubMed2006

The distribution of substance P and met-enkephalin in vocal control nuclei among oscine species and its relation to song complexity.

Substance P (SP) and methionine-enkephalin (ENK) have been reported to appear in song control nuclei of oscine species. However, it remains unknown whether or not SP and ENK location in song control nuclei is correlated with song behavior. To address this issue, the present study first measured two variables for song complexity, i.e., song repertoire sizes, and syllable repertoire sizes in 11 oscine species. Then, we examined the distribution of SP and ENK in four control nuclei, two in the motor pathway, i.e., HVC and the robust nucleus of arcopallium (RA), and the other two in the forebrain pathway, i.e., Area X and the lateral magnocellular nucleus of the anterior nidopallium (LMAN). Finally, we measured the relative amounts of immunoreactivity for SP and ENK in song control nuclei, and tested whether they were correlated with song complexity. Our results showed that: (1) SP and ENK were broadly distributed in the song control nuclei of studied species. However, SP immunohistochemistry was more robust in comparison with ENK, and SP is generally more abundant in the two song learning nuclei than those in the two song producing ones; (2) SP and ENK staining patterns in song control nuclei did not show any obvious phylogenetic relationship among studied oscine species; (3) there was a significant correlation between the relative amounts of immunoreactivity for SP and the song and syllable repertoire sizes. Our results suggest that SP or ENK might be involved in song behavior, such as birdsong learning or memory.

Animals↗
PubMed2004

A method for identifying sounds used in the classification of alarm calls.

In this study, we present a methodology that identifies acoustic units in Gunnison's prairie dog alarm calls and then uses those units to classify the alarm calls and bouts according to the species of predator that was present when the calls were vocalized. While traditional methods measure specific acoustic parameters in order to describe a vocalization, our method uses the variation in the internal structure of a vocalization to define possible information structures. Using a simple representation similar to that used in human speech to identify vowel sounds, a software system was developed that uses this representation to recognize acoustic units in prairie dog alarm calls. These acoustic units are then used to classify alarm calls and their associated bouts according to the species of predator that was present when the alarm calls were vocalized. Identification of bouts with up to 100% accuracy was obtained. This work represents a first step toward revealing the details of how information is encoded in a complex nonhuman communication system. Furthermore, the techniques discussed in this paper are not restricted to a database of prairie dog alarm calls. They could be applied to any animal whose vocalizations include multiple simultaneous frequencies.

Acoustics↗