Discrimination Of Stop Consonants Research Articles

DCDC2 READ1 regulatory element: how temporal processing differences may shape language.

Classic linguistic theory ascribes language change and diversity to population migrations, conquests, and geographical isolation, with the assumption that human populations have equivalent language processing abilities. We hypothesize that spectral and temporal characteristics make some consonant manners vulnerable to differences in temporal precision associated with specific population allele frequencies. To test this hypothesis, we modelled association between RU1-1 alleles of DCDC2 and manner of articulation in 51 populations spanning five continents, and adjusting for geographical proximity, and genetic and linguistic relatedness. RU1-1 alleles, acting through increased expression of DCDC2, appear to increase auditory processing precision that enhances stop-consonant discrimination, favouring retention in some populations and loss by others. These findings enhance classical linguistic theories by adding a genetic dimension, which until recently, has not been considered to be a significant catalyst for language change.

Effects of categorical speech perception during active discrimination of stop-consonants and vowels within the left superior temporal cortex

Effects of categorical speech perception during active discrimination of stop-consonants and vowels within the left superior temporal cortex

Phoneme discrimination of an unrelated language: Evidence for a narrow transfer but not a broad-based bilingual advantage

This study examines monolingual and multilingual individuals’ discrimination of stop consonants in a language to which they had never been exposed: Korean. If bilingualism leads to increased flexibility in phonological categorization, we may see a broad-based bilingual advantage for phoneme discrimination. Using a Korean phoneme discrimination task, we compared 56 adults in four groups: monolingual English, bilingual Spanish, bilingual Armenian, and trilingual. Findings indicate that Spanish–English bilingual individuals scored no better than English monolinguals, and lower than Armenian–English bilingual individuals. In this case, the advantage from early childhood non-English exposure or current bilingualism was found to be specific only to languages with similar phonemic categories. This supports a narrow first/second language to third language transfer view of phoneme discrimination skills.

Physiologic discrimination of stop consonants relates to phonological skills in pre-readers: a biomarker for subsequent reading ability?(†).

Reading development builds upon the accurate representation of the phonological structure of spoken language. This representation and its neural foundations have been studied extensively with respect to reading due to pervasive performance deficits on basic phonological tasks observed in children with dyslexia. The subcortical auditory system – a site of intersection for sensory and cognitive input – is exquisitely tuned to code fine timing differences between phonemes, and so likely plays a foundational role in the development of phonological processing and, eventually, reading. This temporal coding of speech varies systematically with reading ability in school age children. Little is known, however, about subcortical speech representation in pre-school age children. We measured auditory brainstem responses to the stop consonants [ba] and [ga] in a cohort of 4-year-old children and assessed their phonological skills. In a typical auditory system, brainstem responses to [ba] and [ga] are out of phase (i.e., differ in time) due to formant frequency differences in the consonant-vowel transitions of the stimuli. We found that children who performed worst on the phonological awareness task insufficiently code this difference, revealing a physiologic link between early phonological skills and the neural representation of speech. We discuss this finding in light of existing theories of the role of the auditory system in developmental dyslexia, and argue for a systems-level perspective for understanding the importance of precise temporal coding for learning to read.

Speech versus tone processing in compensated dyslexia: Discrimination and lateralization with a dichotic mismatch negativity (MMN) paradigm

This study investigated the possibility of a pervasive auditory-processing deficit in 10 adult dyslexics who had compensated for their reading disability, compared to 10 matched controls. Unlike previous studies [Baldeweg, T., Richardson, A., Watkins, S., Foale, C. & Gruzelier, J. (1999). Impaired auditory frequency discrimination in dyslexia detected with mismatch evoked potentials. Annals of Neurology, 45(4): 495–503], the current EEG study used a dichotic presentation of stimuli in order to probe the relationship between ear advantage and left- and right-hemisphere dominance for processing speech and non-speech stimuli respectively. A dichotic presentation is thought to maximise lateralization effects, as well being a more ecologically valid paradigm. The Mismatch Negativity (MMN) was measured for both speech [consonant–vowel pairs: /ta/ vs. /ka/ and ba/ vs. /da/] and non-speech stimuli (pure tones: 1 kHz vs. 1.2 kHz). Smaller MMNs to tone stimuli were obtained for dyslexics versus controls, but no differences were found for speech stimuli. Controls differentiated between speech and tones, with larger MMNs to tone stimuli. Dyslexics showed significantly greater MMNs to one stop consonant discrimination (/ta/ vs /ka/) than the other (/ba/ vs /da/), but did not differentiate speech from tones, and no or minimal lateralization was found for either group or stimulus type, in line with recent studies [Kershner and Micallef, 1992; Bellis, T.J., Nicol, T., & Kraus, N. (2000). Aging affects hemispheric asymmetry in the neural representation of speech sounds. Journal of Neuroscience, 20, 791–797]. However, analysis of left and right dipole source activity suggested right hemispheric preference for tones in controls, and the lack of such a preference in dyslexics. Lateralization of the auditory system in general may be less specialized in compensated dyslexia, although no specific differences in speech lateralization were seen. The present study also extends previous findings to show that the frequency range over which dyslexics are shown to display impaired frequency discrimination can be extended to 20% (1 kHz vs. 1.2 kHz) if using a dichotic presentation.

Multichannel Compression Hearing Aids: Perceptual Considerations

Multichannel Compression Hearing Aids: Perceptual Considerations

Voice onset time encoding in patients with left and right cochlear implants.

Stop-consonant discrimination was investigated in normal-hearing listeners and cochlear-implanted patients (CIP) by recording auditory evoked potentials (AEPs) to /b epsilon/ and /p epsilon/ syllables. This study demonstrates that: (i) AEPs show time-locked components that mimic the temporal structure of the stimuli, indicating that both patients and control subjects encode those syllables according to the temporal cue (voice onset time) characterizing the voiced/voiceless contrast; (ii) the side of implantation does not affect the general structure of AEPs and /b epsilon/-/p epsilon/ discrimination thresholds (measured separately with a psychophysical procedure); (iii) poor time-locking to the syllables' temporal structure is associated with poor discrimination. This suggests that EEG investigation of temporal-processing provides an objective index of speech perception in CIP and could be used in implanted children.

Perceptual assimilation and categorical discrimination of Korean stop consonants by native Thai speakers

This study examined cross language perceptual assimilation and cross language categorical discrimination. Experiment 1 assessed the native Thai speakers’ ability to discriminate pairs of Korean stop consonants (plain, aspirated, reinforced) at three places of articulation (bilabial, alveolar, and velar). Experiment 2 assessed the perceived relation between the three classes of Korean stop consonants and the three classes of Thai stop consonants (voiced, voiceless unaspirated, voiceless aspirated). Preliminary results suggested that, in general, native Thai speakers assimilated the Korean plain and aspirated stops to the Thai aspirated stops, and the Korean reinforced stops to the Thai unaspirated stops. Results of the categorical discrimination revealed that native Thai speakers were able to successfully discriminate pairs of Korean stop consonants and that there was no relationship between their perceptual assimilation patterns and their ability to discriminate Korean stop consonants. Since the main perceptual cue to the discrimination of Thai stops is voice onset time (VOT), these results suggest that VOT is also the main perceptual cue for the discrimination of Korean stops. Moreover, laryngealization seems to play only a minor role in the perception of Korean stop consonants.

Mismatch negativity potentials in relation to cognitive impairment in schizophrenia

This study investigated the possibility of a pervasive auditory-processing deficit in 10 adult dyslexics who had compensated for their reading disability, compared to 10 matched controls. Unlike previous studies [Baldeweg, T., Richardson, A., Watkins, S., Foale, C. & Gruzelier, J. (1999). Impaired auditory frequency discrimination in dyslexia detected with mismatch evoked potentials. Annals of Neurology, 45(4): 495–503], the current EEG study used a dichotic presentation of stimuli in order to probe the relationship between ear advantage and left- and right-hemisphere dominance for processing speech and non-speech stimuli respectively. A dichotic presentation is thought to maximise lateralization effects, as well being a more ecologically valid paradigm. The Mismatch Negativity (MMN) was measured for both speech [consonant–vowel pairs: /ta/ vs. /ka/ and ba/ vs. /da/] and non-speech stimuli (pure tones: 1 kHz vs. 1.2 kHz). Smaller MMNs to tone stimuli were obtained for dyslexics versus controls, but no differences were found for speech stimuli. Controls differentiated between speech and tones, with larger MMNs to tone stimuli. Dyslexics showed significantly greater MMNs to one stop consonant discrimination (/ta/ vs /ka/) than the other (/ba/ vs /da/), but did not differentiate speech from tones, and no or minimal lateralization was found for either group or stimulus type, in line with recent studies [Kershner and Micallef, 1992; Bellis, T.J., Nicol, T., & Kraus, N. (2000). Aging affects hemispheric asymmetry in the neural representation of speech sounds. Journal of Neuroscience, 20, 791–797]. However, analysis of left and right dipole source activity suggested right hemispheric preference for tones in controls, and the lack of such a preference in dyslexics. Lateralization of the auditory system in general may be less specialized in compensated dyslexia, although no specific differences in speech lateralization were seen. The present study also extends previous findings to show that the frequency range over which dyslexics are shown to display impaired frequency discrimination can be extended to 20% (1 kHz vs. 1.2 kHz) if using a dichotic presentation.

Detection of silent intervals between noises activating different perceptual channels: some properties of "central" auditory gap detection.

This article describes four experiments on gap detection by normal listeners, with the general goal being to examine the consequences of using noises in different perceptual channels to delimit a silent temporal gap to be detected. In experiment 1, subjects were presented with pairs of narrow-band noise sequences. The leading element in each pair had a center frequency of 2 kHz and the trailing element's center frequency was parametrically varied. Gap detection thresholds became increasingly poor, sometimes by up to an order of magnitude, as the spectral disparity was increased between the noise bursts that marked the gap. These data suggested that gap-detection performance is impoverished when the underlying perceptual timing operation requires a comparison of activity in different perceptual channels rather than a discontinuity detection within a given channel. In experiment 2, we assessed the effect of leading-element duration in within-channel and between-channel gap detection tasks. Gap detection thresholds rose when the duration of the leading element was less than about 30 ms, but only in the between-channel case. In experiment 3, the gap-detection stimulus was redesigned so that we could probe the perceptual mechanisms that might be involved in stop consonant discrimination. The leading element was a wideband noise burst, and the trailing element was a 300-ms bandpassed noise centered on 1.0 kHz. The independent variable was the duration of the leading element, and the dependent variable was the smallest detectable gap between the elements. When the leading element was short in duration (5-10 ms), gap thresholds were close to 30 ms, which is close to the voice onset time that parses some voiced from unvoiced stop consonants. In experiment 4, the generality of the leading-element duration effect in between-channel gap detection was examined. Spectrally identical noises defining the leading and trailing edges of the gap were presented to the same or to different ears. There was a leading-element duration effect only for the between channel case. The mean gap threshold was again close to 30 ms for short leading-element durations. Taken together, the data suggest that gap detection requiring a temporal correlation of activity in different perceptual channels is a fundamentally different task to the discontinuity detection used to execute gap detection performance in the traditional, within-channel paradigm.

Construction of state-dependent dynamic parameters using the maximum likelihood approach: Applications to speech recognition

We present in this paper an integrated view on the speech preprocessing and speech modeling problems in the design of a hidden Markov model (HMM) based speech recognizer. The integrated model we developed in this study generalizes the conventional, currently widely used delta-parameter technique, which has been confined strictly to the preprocessing domain only, in two significant ways. First, the new model contains state-dependent weighting functions responsible for transforming static speech features into the dynamic ones in a slowly time-varying manner. Second, a novel maximum-likelihood based learning algorithm is developed for the model that allows joint optimization of the state-dependent weighting functions and the remaining conventional HMM parameters. The experimental results obtained from a standard TIMIT phonetic classification task provide preliminary evidence for the effectiveness of our new, general approach to the use of the dynamic characteristics of speech spectra. The results demonstrate that the new approach is most effective for discrimination of stop consonants exhibiting the fastest and most conspicuous dynamic patterns.

Acoustic parameters for place of articulation identification and classification of Spanish unvoiced stops

The analysis of the acoustic parameters which best summarize the cues to phone discrimination for the language under consideration should be a previous step in acoustic-phonetic decoding, regardless of the methodology to be used. The Spanish language has not been widely analyzed from this point of view. This work deals with the acoustic discrimination of Spanish stop consonants. Our main goal was to find a reliable and reduced set of parameters for place of articulation identification of Spanish unvoiced stops. On the basis of the obtained parameters, two automatic classifiers were developed and tested. Only the acoustic features of the burst segment, automatically segmented from the speech waveform, were considered in the parameter estimation. The analysis of these features was carried out in both the time and frequency domains over a CV context corpus uttered by 6 speakers. In the first case, the classifier was designed as a procedural form. Alternatively, in the second case a statistical classifier was obtained from a previous automatic discriminant analysis of the parameters. Both classifiers were tested over a CV context corpus uttered by 40 new speakers not included in the analysis corpus, which resulted in a good rate of identification.

Substance-related disorders, psychopathology and HIV-related problems in Italy. A clinical research

This study investigated the possibility of a pervasive auditory-processing deficit in 10 adult dyslexics who had compensated for their reading disability, compared to 10 matched controls. Unlike previous studies [Baldeweg, T., Richardson, A., Watkins, S., Foale, C. & Gruzelier, J. (1999). Impaired auditory frequency discrimination in dyslexia detected with mismatch evoked potentials. Annals of Neurology, 45(4): 495–503], the current EEG study used a dichotic presentation of stimuli in order to probe the relationship between ear advantage and left- and right-hemisphere dominance for processing speech and non-speech stimuli respectively. A dichotic presentation is thought to maximise lateralization effects, as well being a more ecologically valid paradigm. The Mismatch Negativity (MMN) was measured for both speech [consonant–vowel pairs: /ta/ vs. /ka/ and ba/ vs. /da/] and non-speech stimuli (pure tones: 1 kHz vs. 1.2 kHz). Smaller MMNs to tone stimuli were obtained for dyslexics versus controls, but no differences were found for speech stimuli. Controls differentiated between speech and tones, with larger MMNs to tone stimuli. Dyslexics showed significantly greater MMNs to one stop consonant discrimination (/ta/ vs /ka/) than the other (/ba/ vs /da/), but did not differentiate speech from tones, and no or minimal lateralization was found for either group or stimulus type, in line with recent studies [Kershner and Micallef, 1992; Bellis, T.J., Nicol, T., & Kraus, N. (2000). Aging affects hemispheric asymmetry in the neural representation of speech sounds. Journal of Neuroscience, 20, 791–797]. However, analysis of left and right dipole source activity suggested right hemispheric preference for tones in controls, and the lack of such a preference in dyslexics. Lateralization of the auditory system in general may be less specialized in compensated dyslexia, although no specific differences in speech lateralization were seen. The present study also extends previous findings to show that the frequency range over which dyslexics are shown to display impaired frequency discrimination can be extended to 20% (1 kHz vs. 1.2 kHz) if using a dichotic presentation.

High-performance alphabet recognition

Alphabet recognition is needed in many applications for retrieving information associated with the spelling of a name, such as telephone numbers, addresses, etc. This is a difficult recognition task due to the acoustic similarities existing between letters in the alphabet (e.g., the E-set letters). This paper presents the development of a high-performance alphabet recognizer that has been evaluated on studio quality as well as on telephone-bandwidth speech. Unlike previously proposed systems, the alphabet recognizer presented is based on context-dependent phoneme hidden Markov models (HMMs), which have been found to outperform whole-word models by as much as 8%. The proposed recognizer incorporates a series of new approaches to tackle the problems associated with the confusions occurring between the stop consonants in the E-set and the confusions between the nasals (i.e., letters M and N). First, a new feature representation is proposed for improved stop consonant discrimination, and second, two subspace approaches are proposed for improved nasal discrimination. The subspace approach was found to yield a 45% error-rate reduction in nasal discrimination. Various other techniques are also proposed, yielding a 97.3% speaker-independent performance on alphabet recognition and 95% speaker-independent performance on E-set recognition, A telephone alphabet recognizer was also developed using context-dependent HMMs. When tested on the recognition of 300 last names (which are contained in a list of 50,000 common last names) spelled by 300 speakers, the recognizer achieved 91.7% correct letter recognition with 1.1% letter insertions.

The effect of multichannel compression on vowel and stop-consonant discrimination in normal-hearing and hearing-impaired subjects.

Multichannel compression (MCC) processing can alter the speech spectrum, perhaps reducing spectral contrasts that are important for the discrimination of certain speech sounds. The effect of MCC processing on the discrimination of vowels and voiced stop consonants was studied. Vowels and voiced stop consonants were MCC-processed in two ways: 1) FLAT MCC having the same compression ratio in each channel, and 2)SHAPED MCC having compression ratios in each channel adjusted to the auditory area of the particular subject. The stimuli were processed both ways using 2, 4, 8, 16, and 31 independent compression channels. Unprocessed and linearly amplified stimuli were used as control conditions. Normal-hearing and hearing-impaired subjects were tested for changes in discrimination performance as a function of the MCC processing parameters. When the MCC processing was adjusted specifically for an individual hearing impared subject, no negative effect of increasing numbers of channels (2 to 31)was found. In the case of FLAT MCC processing, increasingly degraded discrimination performance was found for both subject groups as the compression ratio increased and as the number of channels increased. There was also a strong interaction between the effects of the number of channels and the compression ratio, with the negative effects of increasing numbers of channels being much greater at the highest compression ratio. Negative effects of MCC were found only for very extreme MCC conditions. MCC processing with compression ratios adjusted in each channel for the individual subject, and having as many as 31 channels, revealed no negative effects on vowel or voiced stop-consonant discrimination. These results do not support the prevalent view that MCC with more than two or three channels will be detrimental and should encourage further research on MCC processing with larger numbers of channels.

Discrimination of multichannel-compressed stop consonants

The effect of full-range multichannel compression (MCC) on stop consonant discrimination was studied. For normal-hearing subjects MCC was fit to three hypothetical flat losses, with thresholds ranging from 70 to 90 dB SPL, and one hypothetical sloped loss, with thresholds normal at 500 Hz and 90 dB SPL at 4 kHz. Hearing-impaired subjects were tested with the flat MCC as well as MCC fit to the subject’s hearing loss. The MCC had compression ratios from 1.75 to 7.00, numbers of channels from 2 to 31, and Robinson–Huntington compression [C. E. Robinson and D. A. Huntington, J. Acoust. Soc. Am. 54, 314 (1973)] with 10-ms time windows. Unprocessed stimuli and frequency-equalized linear amplification were control conditions. Deleterious effects of MCC on discrimination of voice onset time (VOT) were minimal. Normal-hearing subjects had difficulty with stop-consonant place discrimination in the most severe compression conditions. Hearing-impaired subjects needed either fitted MCC or frequency-equalized linear amplification to perform consistent place discriminations on these synthetic vowel–consonant–vowel (VCV) syllables. Complete results and their implications for the application of MCC in hearing aids will be discussed. [Work supported by Department of Veterans Affairs.]

Modeling phoneme perception. II: A model of stop consonant discrimination.

Combining elements from two existing theories of speech sound discrimination, dual process theory (DPT) and trace context theory (TCT), a new theory, called phoneme perception theory, is proposed, consisting of a long-term phoneme memory, a context-coding memory, and a trace memory, each with its own time constants. This theory is tested by means of stop-consonant discrimination data in which interstimulus interval (ISI; values of 100, 300, and 2000 ms) is an important variable. It is shown that discrimination in which labeling plays an important part (2IFC and AX between category) benefits from increased ISI, whereas discrimination in which only sensory traces are compared (AX within category), decreases with increasing ISI. The theory is also tested on speech discrimination data from the literature in which ISI is a variable [Pisoni, J. Acoust. Soc. Am. 36, 277-282 (1964); Cowan and Morse, J. Acoust. Soc. Am. 79, 500-507 (1986)]. It is concluded that the number of parameters in trace context theory is not sufficient to account for most speech-sound discrimination data and that a few additional assumptions are needed, such as a form of sublabeling, in which subjects encode the quality of a stimulus as a member of a category, and which requires processing time.

Modeling phoneme perception. I: Categorical perception.

On the basis of a number of vowel and stop-consonant discrimination experiments (AX and 2IFC fixed and roving) with natural stimuli, it is concluded that stop-consonant perception is highly categorical: there were few significant differences between the discrimination results and the phoneme identification results. Moreover, the discrimination and identification response maxima differed significantly from the other data points. Vowel perception was much less categorical: the maxima in the functions were much less significant, and there were significant differences between the various paradigms. Consonant discrimination was much less (if at all) subject to range effects than vowel discrimination. All these results point to different memory types for stop consonants and vowels, and, consequently, to a combination of two different theories of speech sound discrimination: dual-process theory (DPT) for consonants, and trace-context theory (TCT) for vowels.

Age-related differences in processing dynamic acoustic cues to initial stops.

The present study examines possible age-related differences in the ability to process rapidly changing acoustic information in the identification and discrimination of initial stop consonants. As described in Fox etal. [J. Acoust. Soc. Am. 89, 1935(A) (1991)], older adults show lower accuracy rates in identifying both consonants and vowels in so-called ‘‘silent-center’’ tokens. Such results are compatible with the suggestion that older listeners have greater difficulty than younger listeners in processing dynamic acoustic cues, such as those represented by consonant transitions. Two sets of stimuli were created: one set represented a 7-step [beh]–[deh] continuum with a 40-ms transition followed by a 150-ms steady-state vowel; the second set was composed of a 7-step [beh]–[deh] continuum with the same transition followed by a 10-ms vowel. There were two sets of normal hearing listeners including 15 listeners aged 20–24 and 15 listeners aged 60–75. There was an identification task and two AX discrimination tasks (with either a 500- or 2000-ms ISI). Older listeners showed shallower slopes in their identification functions than did the younger listeners, particularly in the stimuli composed primarily of formant transitions. In the discrimination task, older listeners were significantly less sensitive to formant transition differences than were the younger listeners, but there were no significant differences related to interstimulus interval. [Work supported, in part, by an NIA grant to R. Fox.]

Vocal-auditory functions of the chimpanzee: consonant perception

The perception of consonants which were followed by the vowel [a] was studied in chimpanzees and humans, using a reaction time task in which reaction times for discrimination of syllables were taken as an index of similarity between consonants. Consonants used were 20 natural French consonants and six natural and synthetic Japanese stop consonants. Cluster and MDSCAL analyses of reaction times for discrimination of the French consonants suggested that the manner of articulation is the major determinant of the structure of the perception of consonants by the chimpanzees. Discrimination of stop consonants suggested that the major grouping in the chimpanzees was by voicing. The place of articulation from the lips to the velum was reproduced only in the perception of the synthetic unvoiced stop consonants in the two dimensional MDSCAL space. The phoneme-boundary effect (categorical perception) for the voicing and place-of-articulation features was also examined by a chimpanzee using synthetic [ga]-[ka] and [ba]-[da] continua, respectively. The chimpanzee showed enhanced discriminability at or near the phonetic boundaries between the velar voiced and unvoiced and also between the voiced bilabial and alveolar stops. These results suggest that the basic mechanism for the identification of consonants in chimpanzees is similar to that in humans, although chimpanzees are less accurate than humans in discrimination of consonants.