The perceptual weighting of speech-related acoustic cues for 3 & 1/2-year-old children differs from that of adults: Results using natural and synthetic stimuli

Previous studies have found that children’s judgments of syllable-initial /s/ and / ∫ / are more related to the vocalic F2 transition and less related to the fricative-noise spectrum than are adults’ judgments [Nittrouer & Studdert- Kennedy, JSHR, 30 (1987); Nittrouer, J. Phon., 20 1992]. These results have been taken as evidence that young children organize linguistic input in units more closely approximating syllable size than phoneme size. Furthermore, such results have led to a model of speech development proposing that children’s weighting of the acoustic cues for phonemic categories changes as they gain linguistic experience, with a general shift in weighting away from dynamic acoustic parameters (those associated with overall syllable production) towards more static acoustic parameters (those associated with the individual phonemic segments of which the syllable is composed). The present study investigated identification by adults and by 3 & 1/2-year-olds of syllable-initial fricatives for stimuli with either natural or synthetic vocalic portions. The two goals of this work were (1) to see if previous findings indicating children’s enhanced weighting of formant transitions and diminished weighting of fricative-noise spectra could be replicated for stimuli with natural vocalic portions, and (2) to see if these same patterns would be demonstrated for stimuli with synthetic vocalic portions. Results for children showed that the previously observed patterns of weighting of speech-relevant acoustic information held for stimuli with natural vocalic portions only. For stimuli with synthetic vocalic portions, children’s results resembled those of adults. That is, their judgments of fricative identity were more strongly related to the fricative-noise spectrum and less strongly related to the vocalic F2 transition than those judgments had been for stimuli with natural vocalic portions. It was concluded that children’s weighting schemes are not simply the consequence of immature psychoacoustic capacities, and that certain schemes are specific to speech stimuli

Phonetic categorisation and cue weighting in adolescents with Specific Language Impairment (SLI)

This study investigates phonetic categorisation and cue weighting in adolescents and young adults with Specific Language Impairment (SLI). We manipulated two acoustic cues, vowel duration and F1 offset frequency, that signal word-final stop consonant voicing ([t] and [d]) in English. Ten individuals with SLI (14.0–21.4 years), 10 age-matched controls (CA; 14.6–21.9 years) and 10 non-matched adult controls (23.3–36.0 years) labelled synthetic CVC non-words in an identification task. The results showed that the adolescents and young adults with SLI were less consistent than controls in the identification of the good category representatives. The group with SLI also assigned less weight to vowel duration than the adult controls. However, no direct relationship between phonetic categorisation, cue weighting and language skills was found. These findings indicate that some individuals with SLI have speech perception deficits but they are not necessarily associated with oral language skills

Native Speaker Perceptions of Accented Speech: The English Pronunciation of Macedonian EFL Learners

The paper reports on the results of a study that aimed to describe the vocalic and consonantal features of the English pronunciation of Macedonian EFL learners as perceived by native speakers of English and to find out whether native speakers who speak different standard variants of English perceive the same segments as non-native. A specially designed computer web application was employed to gather two types of data: a) quantitative (frequency of segment variables and global foreign accent ratings on a 5-point scale), and b) qualitative (open-ended questions). The result analysis points out to three most frequent markers of foreign accent in the English speech of Macedonian EFL learners: final obstruent devoicing, vowel shortening and substitution of English dental fricatives with Macedonian dental plosives. It also reflects additional phonetic aspects poorly explained in the available reference literature such as allophonic distributional differences between the two languages and intonational mismatch

The use of acoustic cues in phonetic perception: Effects of spectral degradation, limited bandwidth and background noise

Hearing impairment, cochlear implantation, background noise and other auditory degradations result in the loss or distortion of sound information thought to be critical to speech perception. In many cases, listeners can still identify speech sounds despite degradations, but understanding of how this is accomplished is incomplete. Experiments presented here tested the hypothesis that listeners would utilize acoustic-phonetic cues differently if one or more cues were degraded by hearing impairment or simulated hearing impairment. Results supported this hypothesis for various listening conditions that are directly relevant for clinical populations. Analysis included mixed-effects logistic modeling of contributions of individual acoustic cues for various contrasts. Listeners with cochlear implants (CIs) or normal-hearing (NH) listeners in CI simulations showed increased use of acoustic cues in the temporal domain and decreased use of cues in the spectral domain for the tense/lax vowel contrast and the word-final fricative voicing contrast. For the word-initial stop voicing contrast, NH listeners made less use of voice-onset time and greater use of voice pitch in conditions that simulated high-frequency hearing impairment and/or masking noise; influence of these cues was further modulated by consonant place of articulation. A pair of experiments measured phonetic context effects for the "s/sh" contrast, replicating previously observed effects for NH listeners and generalizing them to CI listeners as well, despite known deficiencies in spectral resolution for CI listeners. For NH listeners in CI simulations, these context effects were absent or negligible. Audio-visual delivery of this experiment revealed enhanced influence of visual lip-rounding cues for CI listeners and NH listeners in CI simulations. Additionally, CI listeners demonstrated that visual cues to gender influence phonetic perception in a manner consistent with gender-related voice acoustics. All of these results suggest that listeners are able to accommodate challenging listening situations by capitalizing on the natural (multimodal) covariance in speech signals. Additionally, these results imply that there are potential differences in speech perception by NH listeners and listeners with hearing impairment that would be overlooked by traditional word recognition or consonant confusion matrix analysis

Auditory and speech processing in specific language impairment (SLI) and dyslexia

This thesis investigates auditory and speech processing in Specific Language Impairment (SLI) and dyslexia. One influential theory of SLI and dyslexia postulates that both SLI and dyslexia stem from similar underlying sensory deficit that impacts speech perception and phonological development leading to oral language and literacy deficits. Previous studies, however, have shown that these underlying sensory deficits exist in only a subgroup of language impaired individuals, and the exact nature of these deficits is still largely unknown. The present thesis investigates three aspects of auditory-phonetic interface: 1) The weighting of acoustic cues to phonetic voicing contrast 2) the preattentive and attentive discrimination of speech and non-linguistic stimuli and 3) the formation of auditory memory traces for speech and non-linguistic stimuli in young adults with SLI and dyslexia. This thesis focuses on looking at both individial and group-level data of auditory and speech processing and their relationship with higher-level language measures. The groups of people with SLI and dyslexia who participated were aged between 14 and 25 and their performance was compared to a group of controls matched on chronological age, IQ, gender and handedness. Investigations revealed a complex pattern of behaviour. The results showed that individuals with SLI or dyslexia are not poor at discriminating sounds (whether speech or non-speech). However, in all experiments, there was more variation and more outliers in the SLI group indicating that auditory deficits may occur in a small subgroup of the SLI population. Moreover, investigations of the exact nature of the input-processing deficit revealed that some individuals with SLI have less categorical representations for speech sounds and that they weight the acoustic cues to phonemic identity differently from controls and dyslexics

Invariance of speech percepts

A fundamental question is about the invariance of the ultimate, percepts or features. The present paper gives an overall picture of the issues relevant to this question, aiming at finding a solution. A discussion of the main elements contributing to invariance will be made explicit, namely coupling and interaction. The main question will be that of the principles guiding coupling and interaction during perceptual development. The conclusion of this research work is that perceptual invariance appears to be based on a radial representation of the vocal tract around a singular point at which boundaries are context-free, natural and coincide with the neutral vocoid

Production and perception of Libyan Arabic vowels

PhD ThesisThis study investigates the production and perception of Libyan Arabic (LA) vowels by native speakers and the relation between these major aspects of speech. The aim was to provide a detailed acoustic and auditory description of the vowels available in the LA inventory and to compare the phonetic features of these vowels with those of other Arabic varieties. A review of the relevant literature showed that the LA dialect has not been investigated experimentally. The small number of studies conducted in the last few decades have been based mainly on impressionistic accounts. This study consists of two main investigations: one concerned with vowel production and the other with vowel perception. In terms of production, the study focused on gathering the data necessary to define the vowel inventory of the dialect and to explore the qualitative and quantitative characteristics of the vowels contained in this inventory. Twenty native speakers of LA were recorded while reading target monosyllabic words in carrier sentences. Acoustic and auditory analyses were used in order to provide a fairly comprehensive and objective description of the vocalic system of LA. The results showed that phonologically short and long Arabic vowels vary significantly in quality as well as quantity; a finding which is increasingly being reported in experimental studies of other Arabic dialects. Short vowels in LA tend to be more centralised than has been reported for other Arabic vowels, especially with regards to short /a/. The study also looked at the effect of voicing in neighbouring consonants and vowel height on vowel duration, and the findings were compared to those of other varieties/languages. The perception part of the study explored the extent to which listeners use the same acoustic cues of length and quality in vowel perception that are evident in their production. This involved the use of continua from synthesised vowels which varied along duration and/or formant frequency dimensions. The continua were randomised and played to 20 native listeners who took part in an identification task. The results show that, when it comes to perception, Arabic listeners still rely mainly on quantity for the distinction between phonologically long and short vowels. That is, when presented with stimuli containing conflicting acoustic cues (formant frequencies that are typical of long vowels but with short duration or formant frequencies that are typical of short vowels but with long duration), listeners reacted consistently to duration rather than formant frequency. The results of both parts of the study provided some understanding of the LA vowel system. The production data allowed for a detailed description of the phonetic characteristics of LA vowels, and the acoustic space that they occupy was compared with those of other Arabic varieties. The perception data showed that production and perception do not always go hand in hand and that primary acoustic cues for the identification of vowels are dialect- and language-specific

Highly complex syllable structure: A typological and diachronic study

The syllable is a natural unit of organization in spoken language whose strongest cross-linguistic patterns are often explained in terms of a universal preference for the CV structure. Syllable patterns involving long sequences of consonants are both typologically rare and theoretically marginalized, with few approaches treating these as natural or unproblematic structures. This book is an investigation of the properties of languages with highly complex syllable patterns. The two aims are (i) to establish whether these languages share other linguistic features in common such that they constitute a distinct linguistic type, and (ii) to identify possible diachronic paths and natural mechanisms by which these patterns come about in the history of a language. These issues are investigated in a diversified sample of 100 languages, 25 of which have highly complex syllable patterns. Languages with highly complex syllable structure are characterized by a number of phonetic, phonological, and morphological features which serve to set them apart from languages with simpler syllable patterns. These include specific segmental and suprasegmental properties, a higher prevalence of vowel reduction processes with extreme outcomes, and higher average morpheme/word ratios. The results suggest that highly complex syllable structure is a linguistic type distinct from but sharing some characteristics with other proposed holistic phonological types, including stress-timed and consonantal languages. The results point to word stress and specific patterns of gestural organization as playing important roles in the diachronic development of these patterns out of simpler syllable structures

Highly complex syllable structure: A typological and diachronic study

The syllable is a natural unit of organization in spoken language whose strongest cross-linguistic patterns are often explained in terms of a universal preference for the CV structure. Syllable patterns involving long sequences of consonants are both typologically rare and theoretically marginalized, with few approaches treating these as natural or unproblematic structures. This book is an investigation of the properties of languages with highly complex syllable patterns. The two aims are (i) to establish whether these languages share other linguistic features in common such that they constitute a distinct linguistic type, and (ii) to identify possible diachronic paths and natural mechanisms by which these patterns come about in the history of a language. These issues are investigated in a diversified sample of 100 languages, 25 of which have highly complex syllable patterns. Languages with highly complex syllable structure are characterized by a number of phonetic, phonological, and morphological features which serve to set them apart from languages with simpler syllable patterns. These include specific segmental and suprasegmental properties, a higher prevalence of vowel reduction processes with extreme outcomes, and higher average morpheme/word ratios. The results suggest that highly complex syllable structure is a linguistic type distinct from but sharing some characteristics with other proposed holistic phonological types, including stress-timed and consonantal languages. The results point to word stress and specific patterns of gestural organization as playing important roles in the diachronic development of these patterns out of simpler syllable structures