Vowels In Children Research Articles

Later but Not Weaker: Neural Categorization of Native Vowels of Children at Familial Risk of Dyslexia

Although allophonic speech processing has been hypothesized to be a contributing factor in developmental dyslexia, experimental evidence is limited and inconsistent. The current study compared the categorization of native similar sounding vowels of typically developing (TD) children and children at familial risk (FR) of dyslexia. EEG response was collected in a non-attentive passive oddball paradigm from 35 TD and 35 FR Dutch 20-month-old infants who were matched on vocabulary. The children were presented with two nonwords “giep” [ɣip] and “gip” [ɣIp] that contrasted solely with respect to the vowel. In the multiple-speaker condition, both nonwords were produced by twelve different speakers while in the single-speaker condition, single tokens of each word were used as stimuli. For both conditions and for both groups, infant positive mismatch response (p-MMR) was elicited, and the p-MMR amplitude was comparable between the two groups, although the FR children had a later p-MMR peak than the TD children in the multiple-speaker condition. These findings indicate that FR children are able to categorize speech sounds, but that they may do so in a more effortful way than TDs.

Overruled!: Implicit cues rather than an orthographic rule determine Dutch children's vowel spelling

This study addressed the question why vowel spelling acquisition is relatively difficult for young Dutch spellers. A spelling rule guides vowel spelling, but implicit cues could also play a role. We evaluated the role of phonology, morphology, and orthography. Grade 1 (N = 113) and 2 (N = 59) children were presented with dictations of real and pseudowords differing in the degree of consistency and familiarity. Correct scores of consistent vowel spelling in Grade 1 and 2 students were near ceiling, whereas those for inconsistent vowels were low, even in Grade 2 children, who have had explicit instruction of the spelling rule. Correct scores were affected by phonological and morphological consistency, and orthographic familiarity. Effects of these implicit cues were even more pronounced in Grade 2. Findings indicate that vowel length spelling is difficult to acquire because the explicit spelling rule is overruled by various sources of implicit information.

Children's perception of conversational and clear American-English vowels in noise.

Much of a child's day is spent listening to speech in the presence of background noise. Although accurate vowel perception is important for listeners' accurate speech perception and comprehension, little is known about children's vowel perception in noise. Clear speech is a speech style frequently used by talkers in the presence of noise. This study investigated children's identification of vowels in nonsense words in noise and examined whether adults' use of clear speech would result in the children's more accurate vowel identification. Two female American-English (AE) speaking adults were recorded producing the nonsense word /gəbVpə/ with AE vowels /ɛ-æ-ɑ-ʌ/ in phrases in conversational and clear speech. These utterances were presented to 15 AE-speaking children (ages 5.0-8.5 years) at a signal-to-noise ratio of -6 dB. The children repeated the utterances. Clear-speech vowels were repeated significantly more accurately (87%) than conversational-speech vowels (59%), suggesting that clear speech aids children's vowel identification. Children repeated one talker's vowels more accurately than the other's, and front vowels more accurately than central and back vowels. The findings support the use of clear speech for enhancing adult-to-child communication in AE in noisy environments.

A cross-linguistic study of the effect of perceived gender on the categorization of children's vowels

Previous research has shown that listeners classify acoustically gender-ambiguous vowels differently depending on whether they believe the speaker to be a man or a woman (Johnson, Strand, & D'Imperio, 1999). In real-world listening situations, this tendency could be especially pronounced in the perception of vowels produced by children, as children's voices are inherently gender-ambiguous (Perry, Ohde, & Ashmead, 2001). Given Johnson et al.'s findings, we would predict that adults would categorize children's vowels differently depending on whether they believe the speaker to bes male or female. To examine this hypothesis, a set of experiments was conducted in which native speakers of Cantonese, Japanese, and English categorized a series of synthetic vowels (Menard et al., 2006). These were generated using an articulatory synthesizer, and were meant to represent the vocal tracts of newborn children, 2-, 4-, 5-, 10-, 16-, and 21-year olds. Adults categorized these vowels and provided judgments of the perceived gender and age of the speakers. Preliminary results suggest that speakers of English categorize vowels differently depending on whether they judge the child to be male or female. This tendency is especially marked for the most gender-ambiguous stimulus set, those based on the 10-year-old vocal tract.

Bilateral Cochlear Implants in Infants

The purpose of this feasibility study was to evaluate whether the use of a shorter-length cochlear implant (10 mm) on one ear and a standard electrode (24 mm) on the contralateral ear is a viable bilateral option for children with profound bilateral sensorineural hearing loss. A secondary purpose of this study was to determine whether the ear with the shorter-length electrode performs similarly to the standard-length electrode. Our goal was to provide an option of electrical stimulation that theoretically might preserve the structures of the scala media and organ of Corti. The study is being conducted as a repeated-measure, single-subject experiment. University of Iowa-Department of Otolaryngology. Eight pediatric patients with profound bilateral sensorineural hearing loss between the ages of 12 and 24 months. Nucleus Hybrid S12 10-mm electrode and a Nucleus Freedom implant in the contralateral ear. The Infant-Toddler Meaningful Auditory Integration Scale (IT-MAIS) parent questionnaire, Early Speech Perception, Glendonald Auditory Screening Procedure word test, and Children's Vowel tests will be used to evaluate speech perception and the Minnesota Child Development Inventory and Preschool Language Scales 3 test will be used to evaluate language growth. Preliminary results for 8 children have been collected before and after the operation using the IT-MAIS. All 3 children showed incremental improvements in their IT-MAIS scores overtime. Early Speech Perception, Glendonald Auditory Screening Procedure word test, and Children's Vowel word perception results indicated no difference between the individual ears for the 2 children tested. Performance compared with age-matched children implanted with standard bilateral cochlear implants showed similar results to the children implanted with Nucleus Hybrid S12 10-mm electrode and a Nucleus Freedom implant in contralateral ears. The use of a shorter-length cochlear implant on one ear and a standard-length electrode on the contralateral ear might provide a viable option for bilateral cochlear implantation in children with bilateral profound sensorineural hearing loss. Further study of this patient population will be continued.

Electrophysiological Indices of Discrimination of Long-Duration, Phonetically Similar Vowels in Children With Typical and Atypical Language Development

The authors investigated the neurophysiological bases of vowel perception in children with specific language impairment (SLI) compared with typical language development (TLD) controls using 250-ms phonetically similar vowels. In a previous study, children with SLI showed a poor neurophysiological response (the mismatch negativity [MMN]) to 50-ms versions of these vowels, regardless of whether attention was directed to (attend) or away (passive) from the auditory modality (V. Shafer, M. Morr, H. Datta, D. Kurtzberg, & R. Schwartz, 2005). They hypothesized that longer vowels would allow for improved speech perception. Brain responses were elicited to the vowel contrast in 2 conditions: (a) attend and (b) passive. Behavioral discrimination and identification responses were also examined. Both SLI and TLD groups showed evidence of discrimination (MMN) of the vowels in the attend and passive conditions. Only subtle differences in the scalp topography of a late negative (LN) brain component were observed between groups. The SLI compared with the TLD group showed significantly poorer identification of these long vowels, as found previously with the shorter vowels. Increased vowel duration can improve discrimination in children with SLI. However, poor identification of these longer vowels by some children with SLI suggests a deficit in long-term phonological representations or accessing these representations.

Identification of frequency-shifted vowels

Within certain limits, speech intelligibility is preserved with upward or downward scaling of the spectral envelope. To study these limits and assess their interaction with fundamental frequency (F0), vowels in /hVd/ syllables were processed using the STRAIGHT vocoder and presented to listeners for identification. Identification accuracy showed a gradual decline when the spectral envelope was scaled up or down in vowels spoken by men, women, and children. Upward spectral envelope shifts led to poorer identification of children's vowels compared to adults, while downward shifts had a greater impact on men's vowels compared to women and children. Coordinated shifts (F0 and spectral envelope shifted in the same direction) generally produced higher accuracy than conditions with F0 and spectral envelope shifted in opposite directions. Vowel identification was poorest in conditions with very high F0, consistent with suggestions from the literature that sparse sampling of the spectral envelope may be a factor in vowel identification. However, the gradual decline in accuracy as a function of both upward and downward spectral envelope shifts and the interaction between spectral envelope shifts and F0 suggests the additional operation of perceptual mechanisms sensitive to the statistical covariation of F0 and formant frequencies in natural speech.

Tongue-Palate Contact during Selected Vowels in Children with Cleft Palate

This study reports tongue-palate contact recorded using electropalatography (EPG) during five vowels /i/, /Θ/, /I/, /o/ and / / spoken by school-aged children with cleft palate and a group of normal speakers. All the children had articulation disorders affecting consonants but none had obvious vowel errors. Two measures were taken from the EPG data at the temporal midpoint of the vowels. The first identified the percentage of vowels produced with complete coronal constriction and the second calculated amount of contact. The results showed that children with cleft palate frequently produced the high vowel /i/ with complete constriction, with 40% of /i/ targets articulated in this way. There were lower percentages for /Θ/ and /I/ and no complete constrictions during the lower vowels /o/ and / /. None of the normal speakers produced any vowels with complete constriction. In terms of amount of contact, the vowels ranked /i/ > /Θ/ > /I/ > /o/ > / /, with /i/ having the most and / / the least contact. Although this ranking held for both groups, the cleft group had more contact than normal speakers, especially during high vowels. Complete constriction is viewed as a clinically relevant phenomenon that blocks oral airflow and as a result increases nasal airflow during vowels.

Identification of children's and adults' vowels: intrinsic fundamental frequency, fundamental frequency dynamics, and presence of voicing

Three experiments investigated the role of fundamental frequency (F0) in the perception of vowels produced by children and adults. The stimuli were based on a set of American English vowels recorded in /hVd/ syllables by three groups of children (ages 3, 5, and 7 yr) and adult males and females. Experiment 1 presented natural and synthesized vowels to adult listeners for identification. To determine whether vowel-specific differences inF0 (intrinsic F0) contribute to the accuracy of vowel identification, listeners identified stimuli in which F0was held constant at the mean value across the entire vowel set for a given talker. These manipulations had no effect on identification accuracy, either when F0conditions varied from trial to trial (Experiment 1) or were blocked within a set of trials (Experiment 2). Holding F0constant over the duration of the vowel did not lower accuracy, suggesting that time-varying changes in F0make little contribution to vowel identification. Experiment 3 assessed whether the presence of F0per se provides benefits for vowel identification. This was achieved by replacing the pulsed excitation source of the synthesized voiced vowels with white noise to simulate whispered speech. Identification accuracy was lower for noise-excited than pulse-excited vowels for all talker groups. Differences between noise-excited and voiced vowels were larger for adult males than for children, suggesting that the benefits ofF0 are not due simply to improved specification of the spectrum envelope. Taken together, the results suggest that (1) F0plays a small but complex role in vowel identification in isolated words; (2) the periodicity or harmonicity contributed by F0carries more perceptual weight than either vowel-inherentF0 dynamics or a vowel's intrinsic F0, and (3) F0characteristics (dynamic patterns and intrinsic F0) provide a relatively small contribution to the reduced intelligibility commonly noted for children's vowels.

Time-varying spectral change in the vowels of children and adults.

Recent studies have shown that time-varying changes in formant pattern contribute to the phonetic specification of vowels. This variation could be especially important in children's vowels, because children have higher fundamental frequencies (f0's) than adults, and formant-frequency estimation is generally less reliable when f0 is high. To investigate the contribution of time-varying changes in formant pattern to the identification of children's vowels, three experiments were carried out with natural and synthesized versions of 12 American English vowels spoken by children (ages 7, 5, and 3 years) as well as adult males and females. Experiment 1 showed that (i) vowels generated with a cascade formant synthesizer (with hand-tracked formants) were less accurately identified than natural versions; and (ii) vowels synthesized with steady-state formant frequencies were harder to identify than those which preserved the natural variation in formant pattern over time. The decline in intelligibility was similar across talker groups, and there was no evidence that formant movement plays a greater role in children's vowels compared to adults. Experiment 2 replicated these findings using a semi-automatic formant-tracking algorithm. Experiment 3 showed that the effects of formant movement were the same for vowels synthesized with noise excitation (as in whispered speech) and pulsed excitation (as in voiced speech), although, on average, the whispered vowels were less accurately identified than their voiced counterparts. Taken together, the results indicate that the cues provided by changes in the formant frequencies over time contribute materially to the intelligibility of vowels produced by children and adults, but these time-varying formant frequency cues do not interact with properties of the voicing source.

Phonological and Orthographic Influences on Children's Vowel Spelling

Vowel representations are particularly difficult for children to learn because most vowel phonemes can be spelled in several different ways. Children in Grades 1, 2, and 3 spelled nonwords with an ambiguous vowel and reported their spelling strategies. Analysis of the children's spellings and strategy reports revealed a shift in relying solely on phonological information to considering orthographic information for making vowel letter choices. Implications for vowel spelling development are discussed.

Children's vowel duration and stuttering modification following speech motor training

Children's vowel duration and stuttering modification following speech motor training

Acoustic analysis and perception of vowels in children’s and teenagers’ stuttered speech

The syllable repetitions of 24 child and eight teenage stutterers were investigated to assess whether the vowels neutralize and, if so, what causes this. In both groups of speakers, the vowel in CV syllable repetitions and the following fluent vowel were excised from conversational speech samples. Acoustic analyses showed the formant frequencies of vowels in syllable repetitions to be appropriate for the intended vowel and the duration of the dysfluent vowels to be shorter than those of the fluent vowels for both groups of speakers. The intensity of the fluent vowels was greater than that of the dysfluent vowels for the teenagers but not the children: For both age groups, excitation waveforms obtained by inverse filtering showed that the excitation spectra associated with dysfluent vowels fell off more rapidly with frequency than did those associated with the fluent vowels. The fundamental frequency of the children's dysfluent speech was higher than their fluent speech while there was no difference in the teenager's speech. The relationship between the intensities of the glottal volume velocities was the same as that of the speech waveforms. Perceptual tests were also conducted to assess whether duration and the differences found in the source excitation would make children's vowels sound neutral. The experiments show that in children neither vowel duration nor fundamental frequency differences cause the vowels to be perceived as neutral. The results suggest that the low intensity and characteristics of the source of excitation which cause vowels to sound neutral may only occur in late childhood. Furthermore, monitoring stuttered speech for the emergence of neutral vowels may be a way of indexing the progress of the disorder.

Modifications in deaf children's vowel production: perceptual evidence.

This study examined the perceived changes in vowel articulation by profoundly deaf children as a function of the method of teaching: with visual feedback provided by the Computer Vowel Trainer (CVT) vs conventional methods. The assessment carried out by experienced listeners consisted in marking the sounds heard on the vowel quadrilateral. It was found that changes in perception were feedback and age dependent: younger children taught with the CVT were perceived as displaying more mobility in articulation and they approximated more closely the target vowels than their control counterparts or older children. Progress was evident in particular for back and central vowels. Analysis of perceived discrepancies between target and judged vowels, too, suggested that visual feedback was beneficial: perception of experimental children's utterances showed a marked reduction in substitutions with central vowels, a characteristic pattern of deaf speech. Comparison of these findings with the results yielded by the judgement of the same items by naive listeners indicated broad agreement between the two categories of assessors. Results were discussed in terms of the perceptual and articulatory intervening variables with reference to the specific advantages and constraints imposed by evaluating vowel quality on the vowel plane.

Acoustic characteristics of flap productions by American English‐speaking children and adults

Acoustic characteristics of underlying, intervocalic /d/ and /t/ flaps produced by a number of children and adults were studied to determine whether children's flaps showed similar properties to their other speech segments when compared with adults' productions. Closure durations of flaps and other consonents and a number of vowel durations were measured using a laboratory mini‐computer system. Contrasts such as “pudding/putting” and “writer/rider” produced in a carrier phrase were elicited using pictures so that no auditory model would be available for the children. Preliminary results showed that flaps from underlying /d/ were about 10% longer in duration than flaps from underlying /t/ for both the children and adults. Although stressed vowels preceding underlying /d/ flaps were longer in duration than those preceding underlying /t/ flaps for both groups, this contrast was substantially greater for the adults. It was also observed that flap durations were approximately 40% longer for the children than for the adults, while the durations of the children's vowels and nonflap consonant productions were more comparable to the adult's durations for those segments.

Quantal characteristics and motor control in early child speech

In the late babbling and early word stages of development, the vowels that children produce are not as “well formed” as those of adults. Taking into consideration the higher formant frequencies of children's vowels, which follow from their shorter supralaryngeal vocal tracts, one finds, for example, that F1 of an [i] is higher than it should be relative to F2 at ages of approximately 70 weeks. This is presumably a consequence of the shorter length of the child's pharynx relative to the oral cavity (King, 1952). As the child matures, the relative position of F1 and F2 of [i] come closer to the adult model. In addition, there is a greater variability in the formant frequencies of all vowels at earlier ages. This may be a consequence of the child's pharynx not being equal in length to the oral cavity, making vowels like [i] less characteristically “quantal” (Stevens, 1952). This variation may also be due to a lack of motor control. In this study, the relative importance of quantalness versus motor control is assessed by comparing the variability of quantal vowels, such as [i] and [u], with other vowels as a function of age.

Intrinsic vowel duration and formant frequencies: Data from speech acquisition

The vowels of American English are specified by particular formant frequency patterns and durations. Acoustic data derived from the speech of children between the ages of 69 and 145 weeks show that the vowels that they produce in meaningful words often have mismatched formant frequency patterns and durations. The formant frequency pattern of an intended [i], for example, may have the duration of an [1]. Psychoacoustic experiments using computer edited stimuli derived from the children's vowel productions demonstrate the interaction of formant frequency patterns and duration as acoustic cues to vowel perception. Intrinsic vowel duration and control of the supralaryngeal vocal tract appear to be independent parameters in the acquisition of speech. Hypothetical phonetic features like Tenseness thus can not be causally linked to relative vowel duration.

Vowel and speaker identification in natural and synthetic speech.

The study describes the results of a listening test in which subjects were required to identify both the vowel and the sex of the speaker. Ten monophthongal American English vowels were selected: /i I ε æ a u Λ 3/. These vowels were produced by a male speaker, a female speaker, and a child. Formant values were read from spectrograms made of these vowels and used for synthesizing the same 30 vowels on a Glace-Holmes synthesizer. A third set of vowels was generated synthetically using formant and fundamental frequency values reported by Peterson and Barney (1952). In this set, the fundamental frequency characteristic of male, female and children's voices was combined with male, female and children's formants. The set of 150 stimuli was presented to 60 listeners, who were asked to identify the speakers and vowels. Overall speaker identification scores were higher than overall vowel identification scores for both normal speakers and vowels synthesized from measurements; for the Peterson-Barney set, the scores were approximately the same. The highest overall correct score was 88.3%, obtained for the normal male speaker; the lowest correct score was 31.0%, obtained for children's vowels synthesized from measurements.

Acoustical features of children's vowel sounds: development by chronological age versus bone age.

The acoustic development of four vowel sounds in children's speech during the first six years was studied to determine whether statistically significant differences in formant frequency are apparent when chronological age is compared with a measure of physiological age. Thirty pre-school children were recorded in free verbalization situations. Representative productions of the four vowels /i/, /æl /α/, /u/ were analysed with a sound spectrograph and measurements made of Formants 1 and 2. Results indicate that when the formant frequency measurements are compared as chronological age v. physiological age, no difference is found. It is concluded that grouping children by a measure of physiological maturity, rather than by chronological age, does not change the final results when examining the development of formant frequencies.