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PubMed2005

Brain potentials to native and non-native speech contrasts in 7- and 11-month-old American infants.

Abstract Behavioral data establish a dramatic change in infants' phonetic perception between 6 and 12 months of age. Foreign-language phonetic discrimination significantly declines with increasing age. Using a longitudinal design, we examined the electrophysiological responses of 7- and 11-month-old American infants to native and non-native consonant contrasts. Analyses of the event-related potentials (ERP) of the group data at 7 and at 11 months of age demonstrated that infants' discriminatory ERP responses to the non-native contrast are present at 7 months of age but disappear by 11 months of age, consistent with the behavioral data reported in the literature. However, when the same infants were divided into subgroups based on individual ERP components, we found evidence that the infant brain remains sensitive to the non-native contrast at 11 months of age, showing differences in either the P150-250 or the N250-550 time window, depending upon the subgroup. Moreover, we observed an increase in infants' responsiveness to native language consonant contrasts over time. We describe distinct neural patterns in two groups of infants and suggest that their developmental differences may have an impact on language development.

Acoustic Stimulation↗
PubMed1996

A combination of vocal fo dynamic and summary features discriminates between three pragmatic categories of infant-directed speech.

To assess the relative contribution of dynamic and summary features of vocal fundamental frequency (f0) to the statistical discrimination of pragmatic categories in infant-directed speech, 49 mothers were instructed to use their voice to get their 4-month-old baby's attention, show approval, and provide comfort. Vocal f0 from 621 tokens was extracted using a Computerized Speech Laboratory and custom software. Dynamic features were measured with convergent methods (visual judgment and quantitative modeling of f0 contour shape). Summary features were f0 mean, standard deviation, and duration. Dynamic and summary features both individually and in combination statistically discriminated between each of the pragmatic categories. Classification rates were 69% and 62% in initial and cross-validation DFAs, respectively.

Adult↗
PubMed2006

Social complexity can drive vocal complexity: group size influences vocal information in Carolina chickadees.

One hypothesis to explain variation in vocal communication in animal species is that the complexity of the social group influences the group's vocal complexity. This social-complexity hypothesis for communication is also central to recent arguments regarding the origins of human language, but experimental tests of the hypothesis are lacking. This study investigated whether group size, a fundamental component of social complexity, influences the complexity of a call functioning in the social organization of Carolina chickadees, Poecile carolinensis. In unmanipulated field settings, calls of individuals in larger groups had greater complexity (more information) than calls of individuals in smaller groups. In aviary settings manipulating group size, individuals in larger groups used calls with greater complexity than individuals in smaller groups. These results indicate that social complexity can influence communicative complexity in this species.

Animals↗
PubMed1996

Spectral factors in the perception of vowel quantity in Icelandic.

Previous research has shown that the ratio of vowel to rhyme (vowel + consonant) duration is a major cue for quantity in Icelandic. In particular it serves as a higher-order invariant which enables the listener to disentangle those durational transformations of the speech signal which are "extrinsic" (e.g. due to changes in speaking rate) from those which are "intrinsic" to the phonemic message, involving a change of phonemic quantity. Previous research has been based on speech segment contrasts which are purely durational, involving vowels with a uniform spectrum whether phonemically long or short, such as [a] or [I]. This paper looks at the role of spectral factors in vowels which are spectrally dissimilar in their long and short varieties. It is shown that in these cases the spectral differences can be sufficiently great to override the previously established relational invariant for quantity. The implications of this finding for a model of quantity perception are discussed.

Adult↗
PubMed1987

Childhood epileptic speech disorder: prolonged, isolated deficit of prosodic features.

A 7 1/2-year-old left-handed boy developed partial complex seizures with a left temporal electroencephalographic focus, together with prolonged, isolated deterioration of speech. Seizures stopped completely with anticonvulsant therapy and speech quickly returned to normal. Quantitative analysis of speech production and the language examination when the disorder was at its worst and after recovery allowed the documentation of the slowing and monotony of speech, in the absence of aphasic disturbance in comprehension and expression. This case illustrates the possibility of prolonged yet rapidly reversible speech deficit as an isolated manifestation of epilepsy and documents an as yet unreported feature of speech disorders of epileptic origin.

Aphasia↗
PubMed1990

Cervical auscultation of suckle feeding in newborn infants.

The authors recorded the sound signals during suckle feeding of six normal infants within the first two postnatal days. The sounds were recorded onto a cassette tape-recorder from a small microphone attached to the infant's neck, then displayed on an oscilloscope and analysed by digital signal processing techniques. These displays demonstrated acoustic patterns and temporal relationships which are not otherwise audible. The method and findings are described in detail, and the method should be useful in the clinical investigation of feeding and swallowing problems associated with more subtle neurological impairment and preterm birth.

Auscultation↗
PubMed1995

Correlation of cervical auscultation with physiological recording during suckle-feeding in newborn infants.

Pharyngeal swallows during infant suckle-feeding are associated with a characteristic sequence of sounds audible by stethoscope or by an accelerometer or microphone held over the larynx. In rhythmically feeding term-born neonates, the delineating acoustic elements are discrete sounds which precede and succeed pharyngeal swallows. Digital signal processing shows similarities in morphological detail between the discrete sounds preceding swallows and between those succeeding swallows; those succeeding swallows are more variable in temporal relation to swallows, amplitude and morphological detail. Variations in the pattern of interswallow respiration, including apnea, are correlated with variations in the discrete sounds. Specification of physiological correlates of these internal feeding sounds increases the utility of cervical auscultation as a method of investigation and of clinical observation of feeding.

Auscultation↗
PubMed1989

Effects of alcohol on the acoustic-phonetic properties of speech: perceptual and acoustic analyses.

This report summarizes the results of a series of studies that examined the effects of alcohol on the acoustic-phonetic properties of speech. Audio recordings were made of male talkers producing lists of sentences under a sober condition and an intoxicated condition. These speech samples were then subjected to perceptual and acoustic analyses. In one perceptual experiment, listeners heard matched pairs of sentences from four talkers and were required to identify the sentence that was produced while the talker was intoxicated. In a second perceptual experiment, Indiana State Troopers and college undergraduates were required to judge whether individual sentences presented in isolation were produced in a sober or an intoxicated condition. The results of the perceptual experiments indicated that groups of listeners can significantly discriminate between speech samples produced under sober and intoxicated conditions. For acoustic analyses, digital signal processing techniques were used to measure acoustic-phonetic changes that took place in speech production when the talker was intoxicated. The results of the acoustical analyses revealed consistent and well-defined changes in speech articulation between sober and intoxicated conditions. Because speech production requires fine motor control and timing of the articulators, it may be possible to use acoustic-phonetic measures as sensitive indices of sensory-motor impairment due to alcohol consumption.

Adult↗
PubMed1993

Motor impairment in Wilson's disease, II: Slowness of speech.

The maximal syllable production rate (MSPR) and the ability to reproduce a given target frequency in the 1 to 8 Hz range by repeating the short syllable "ta" was tested in 20 patients with Wilson's disease (WD) and 20 normal subjects. MSPR was significantly reduced in the WD-patients. In the 1 to 5 Hz range normal subjects as well as WD-patients tended to produce slightly higher frequencies than the target frequencies. This hastening was maximal in normals between 4 to 5 Hz whereas in the WD-patients hastening mainly occurred between 3 to 4 Hz. The test results showed a considerable variation across the patients. This variation can be interpreted on the basis of the theory of coupled oscillators. Comparison of speech and finger movements revealed a highly significant correlation between MSPR and the highest possible frequency of voluntary alternating index finger movements. As an application of the presented test treatment effects on speech movements were demonstrated.

Adolescent↗
PubMed1988

Speech characteristics as indicators of depressive illness.

Measures of the rate of change of voice fundamental frequency, fundamental frequency variability, reading and counting times, and different measures of pause time were compared in 28 depressed patients and 13 healthy controls. The fundamental frequency variables were lower in the depressed group, and the pauses between the interviewer's questions and the patient's answers were longer. The remaining speech variables, including the summed duration of interdigit pauses in counting from 1 to 10 (speech pause time), did not differ between the groups.

Adult↗
PubMed2005

Diagnosis of ankylosis in permanent incisors by expert ratings, Periotest and digital sound wave analysis.

The objectives of this investigation were to: (i) assess the reliability of expert raters to detect ankylosis from recordings of percussion sounds, (ii) measure differences in Periotest values (PTV) between ankylosed and non-ankylosed incisors and (iii) identify characteristic differences in recorded percussion sounds from ankylosed and non-ankylosed incisors using digital sound wave analysis. A convenience sample of healthy children (age range 7-18 years) was invited to participate. Ankylosis group children had one or more documented ankylosed maxillary incisors. Control group children had intact, non-ankylosed incisors. Digital recordings of percussion sounds and PTV were acquired for each incisor of interest. Four experienced pediatric dentists rated the randomized percussion sound pairs for the presence of ankylosis. Percussion sounds were also subjected to digital sound wave analysis. Overall agreement for the expert raters was substantial (kappa = 0.7). Intra-rater agreement was substantial to almost perfect (kappa = 0.6-0.9). Diagnosis of ankylosis demonstrated sensitivity of 76-92% and specificity of 74-100%. PTV from ankylosed incisors were statistically lower than PTV from non-ankylosed incisors. Ankylosed incisor digital sound wave signals exhibited significantly more energy in high-frequency bands than non-ankylosed incisors. This investigation demonstrated that: (i) experienced pediatric dentists reliably detected ankylosis by percussion sound alone; (ii) PTV for ankylosed incisors were statistically lower than PTV from non-ankylosed incisors; and (iii) ankylosed incisors exhibited a higher proportion of their signal energy in high-frequency bands.

Adolescent↗
PubMedDate not supplied

Resolution of MRS applied to the characterization of hard-rock aquifers.

The performance of the Magnetic Resonance Sounding (MRS) method applied to the investigation of heterogeneous hard-rock aquifers was studied. It was shown using both numerical modeling and field measurements that MRS could be applied to the investigation of the weathered part of hard-rock aquifers when the product of the free water content multiplied by the thickness of the aquifer is >0.2 (for example, 10-m-thick layer with a 2% water content). Using a currently available one-dimensional MRS system, the method allows the characterization of two-dimensional subsurface structures with acceptable accuracy when the size of the subsurface anomaly is equal to or greater than the MRS loop. However, the fractured part of hard-rock aquifers characterized by low effective porosity (<0.5%) cannot be resolved using currently available MRS equipment. It was found that shallow water in the weathered part of the aquifer may screen MRS signals from deeper water-saturated layers, thus further reducing the possibility of investigating deeper fractured aquifers. A field study using the NUMIS(plus) MRS system developed by IRIS Instruments was carried out on an experimental watershed in southern India. A heterogeneous unconfined aquifer in a gneissic formation was successfully localized, and MRS results were confirmed by drilling shortly after the geophysical study. The top of the aquifer revealed by MRS was found to be in a good agreement with observed static water level measurements in boreholes.

Image Processing, Computer-Assisted↗
PubMed1983

Speech coding: recognizing what we do not hear in speech.

Speech is a highly redundant signal. The redundant nature of speech is important for providing reliable communication over air pathways. A large part of this redundancy is useless for speech communication over digital channels. Speech coding aims at minimizing the information rate needed to reproduce a speech signal with specified fidelity. In this paper, we discuss factors that influence the design of efficient speech coders. The encoding and decoding processes invariably introduce error (noise and distortion) in the speech signal. Inability of the human ear to hear certain kinds of distortions in the speech signal plays a crucial role in producing high-quality speech at low bit rates. The physical difference between the waveforms of a given speech signal and its coded replica generally does not tell us much about the subjective quality of the coded signal. A signal-to-noise ratio as small as 10 dB can be tolerated in the coded signal provided the errors are distributed both in time and frequency domains where they are least audible. Recent work on auditory masking has provided us with new insights for optimizing the performance of speech coders. This paper reviews this work and discusses new speech coding methods that attempt to maximize the perceptual similarity between the original speech signal and its coded replica. These new methods make it possible to reproduce speech signals at very low bit rates with little or no audible distortion.

Cochlea↗
PubMed1983

Coding of the speech spectrum in three time-varying sinusoids.

Recent perceptual experiments with normal adult listeners show that phonetic information can readily be conveyed by sinewave replicas of speech signals. These tonal patterns are made of three sinusoids set equal in frequency and amplitude to the respective peaks of the first three formants of natural-speech utterances. Unlike natural and most synthetic speech, the spectrum of sinusoidal patterns contains neither harmonics nor broadband formants, and is identified as grossly unnatural in voice timbre. Despite this drastic recoding of the short-time speech spectrum, listeners perceive the phonetic content if the temporal properties of spectrum variation are preserved. These observations suggest that phonetic perception may depend on properties of coherent spectrum variation, a second-order property of the acoustic signal, rather than any particular set of acoustic elements present in speech signals.

Humans↗