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Purpose: To examine the developmental course of labial and alveolar manner of articulation contrasts, and to determine how that course may be different for typically developing (TD) children with cochlear implants (CI)., Method: Eight young adults, eight TD 5-8 year-old children, and seven 5-8 year-old children with CIs participated. Labial /ba/-/wa/ and alveolar /da/-/ja/ continua stimuli were presented, with each continuum consisting of nine synthetic stimuli varying in F2 and F3 transition duration. Participants were asked to label the stimuli as either a stop or glide, and responses were analysed for phonetic boundaries and slopes., Result: For the /ba/-/wa/ contrast, children with CIs required longer transition durations compared to TD children or adults to cross from one phoneme category to another. The children with CIs demonstrated less confidence in labelling the stimuli (i.e. less steep slopes) than the TD children or the adults. For the /da/-/ja/ contrast, the children with CIs showed less steep slope values than adults., Conclusion: These results suggest that there are differences in the way TD children and children with CIs develop and maintain phonetic categories, perhaps differences in phonetic representation or in linking acoustic and phonetic representations.

Purpose: This study was conducted to determine whether the perceptions of nasal consonants in children with normal hearing and children with cochlear implants were predicted by the discontinuity hypothesis. Methods Four groups participated: 8 adults, 8 children with normal hearing (ages 5-7 years), 8 children with normal hearing (ages 3.5-4 years), and 5 children with cochlear implants (ages 5-7 years). Stimuli were 128 nasal consonant + vowel (/m/ /n/ + /i/ /æ/ /u/ //) syllables produced by a male adult. Each syllable production was edited into 4 segment types: (a) 50-ms murmur, (b) 25-ms murmur + 25-ms transition, (c) 50-ms transition, and (d) full syllable., Results: Developmental effects were observed across listener groups. The children performed better in the 25-ms murmur + 25-ms transition condition, which suggests that they benefit from an integrated perceptual cue. The children wearing cochlear implants performed poorer than children with normal hearing on all segments., Conclusions: Developmental differences in perception of nasal consonants were evident. Children wearing cochlear implants showed weaker integration and perception abilities compared to younger children with normal hearing. As predicted by the discontinuity hypothesis, the segment with the spectral discontinuity provided the strongest perceptual cues to place of articulation of nasals in children with normal hearing.

The purpose of this study was to determine whether children give more perceptual weight than do adults to dynamic spectral cues versus static cues. Listeners were 10 children between the ages of 3;8 and 4;1 (mean 3;11) and ten adults between the ages of 23;10 and 32;0 (mean 25;11). Three experimental stimulus conditions were presented, with each containing stimuli of 30 ms duration. The first experimental condition consisted of unchanging formant onset frequencies ranging in value from frequencies for [i] to those for [a], appropriate for a bilabial stop consonant context. The second two experimental conditions consisted of either an [i] or [a] onset frequency with a 25 ms portion of a formant transition whose trajectory was toward one of a series of target frequencies ranging from those for [i] to those for [a]. Results indicated that the children attended differently than the adults on both the [a] and [i] formant onset frequency cue to identify the vowels. The adults gave more equal weight to the [i]-onset and [a]-onset dynamic cues as reflected in category boundaries than the children did. For the [i]-onset condition, children were not as confident compared to adults in vowel perception, as reflected in slope analyses., (© 2011 Acoustical Society of America)

The general purpose of this research was to describe coarticulation across voiced stop consonant place of articulation in 10 children younger than 2 years of age. A total of 1,182 voiced stop CV productions was analyzed using the locus equation metric, which yielded 3 regression lines that described the relation of F2 onset and F2 vowel for /bV/, /dV/, and /gV/ productions. The results revealed significant differential effects for slope and y-intercept as a function of stop consonant place of articulation. The ordering of the mean slope values for stop consonant place of articulation was /g/>/b/ and /d/, indicating that /g/ was produced with significantly greater coarticulation than /b/ or /d/. However, the unique vowel allophonic pattern of [g] coarticulation reported in the literature for English-speaking adults was generally not learned by these young children. Group and individual coarticulation trends are described in relation to developmental theories of sound acquisition. Results suggest that early coarticulation patterns are phoneme specific.

Purpose: To investigate the holistic versus incremental phonological encoding processes of young children who stutter (CWS; N = 26) and age- and gender-matched children who do not stutter (CWNS; N = 26) via a picture-naming auditory priming paradigm., Method: Children named pictures during 3 auditory priming conditions: neutral, holistic, and incremental. Speech reaction time (SRT) was measured from the onset of picture presentation to the onset of participant response., Results: CWNS shifted from being significantly faster in the holistic priming condition to being significantly faster in the incremental priming condition from 3 to 5 years of age. In contrast, the majority of 3- and 5-year-old CWS continued to exhibit faster SRT in the holistic than the incremental condition., Conclusion: CWS are delayed in making the developmental shift in phonological encoding from holistic to incremental processing, a delay that may contribute to their difficulties establishing fluent speech.

The contribution of the nasal murmur and vocalic formant transition to the perception of the [m]-[n] distinction by adult listeners was investigated for speakers of different ages in both consonant-vowel (CV) and vowel-consonant (VC) syllables. Three children in each of the speaker groups 3, 5, and 7 years old, and three adult females and three adult males produced CV and VC syllables consisting of either [m] or [n] and followed or preceded by [i ae u a], respectively. Two productions of each syllable were edited into seven murmur and transitions segments. Across speaker groups, a segment including the last 25 ms of the murmur and the first 25 ms of the vowel yielded higher perceptual identification of place of articulation than any other segment edited from the CV syllable. In contrast, the corresponding vowel+murmur segment in the VC syllable position improved nasal identification relative to other segment types for only the adult talkers. Overall, the CV syllable was perceptually more distinctive than the VC syllable, but this distinctiveness interacted with speaker group and stimulus duration. As predicted by previous studies and the current results of perceptual testing, acoustic analyses of adult syllable productions showed systematic differences between labial and alveolar places of articulation, but these differences were only marginally observed in the youngest children's speech. Also predicted by the current perceptual results, these acoustic properties differentiating place of articulation of nasal consonants were reliably different for CV syllables compared to VC syllables. A series of comparisons of perceptual data across speaker groups, segment types, and syllable shape provided strong support, in adult speakers, for the "discontinuity hypothesis" [K. N. Stevens, in Phonetic Linguistics: Essays in Honor of Peter Ladefoged, edited by V. A. Fromkin (Academic, London, 1985), pp. 243-255], according to which spectral discontinuities at acoustic boundaries provide critical cues to the perception of place of articulation. In child speakers, the perceptual support for the "discontinuity hypothesis" was weaker and the results indicative of developmental changes in speech production.

The effect of high speech presentation levels on consonant recognition and feature transmission was assessed in eight participants with normal hearing. Consonant recognition in noise (0 dB signal-to-noise ratio) was measured at five overall speech levels ranging from 65 to 100 dB SPL. Consistent with the work of others, overall percent correct performance decreased as the presentation level of speech increased [e.g., G. A. Studebaker, R. L. Sherbecoe, D. M. McDaniel, and C. A. Gwaltney, J. Acoust. Soc. Am. 105(4), 2431-2444 (1999)]. Confusion matrices were analyzed in terms of relative percent information transmitted at each speech presentation level, as a function of feature. Six feature sets (voicing, place, nasality, duration, frication, and sonorance) were analyzed. Results showed the feature duration (long consonant duration fricatives) to be most affected by increases in level, while the voicing feature was relatively unaffected by increases in level. In addition, alveolar consonants were substantially affected by level, while palatal consonants were not. While the underlying mechanisms responsible for decreases in performance with level increases are unclear, an analysis of common error patterns at high levels suggests that saturation of the neural response and/or a loss of neural synchrony may play a role.

The purpose of the current study was to examine the role of syllable duration context as well as static and dynamic acoustic properties in child and adult speech perception. Ten adults and eleven 4-5-year-old children identified a syllable as [ba] or [wa] (stop-glide contrast) in 3 conditions differing in synthetic continua. The 1st condition tested the potential existence of the syllable duration effect in young children, whereas the 2nd and 3rd conditions examined the developmental role of static and dynamic cues, respectively, as related to syllable duration context effects. In the 1st condition, the 1st and 2nd formant transition duration of stimuli varied from those appropriate for [ba] to those appropriate for [wa]. For the 2nd condition, a static burst was added to Condition 1 stimuli. For the 3rd condition, the dynamic transition frequency and transition duration for the first 3 formants varied as appropriate for [ba] and [wa]. In each condition, 3 syllable context durations of 105 ms, 170 ms, and 315 ms were tested. The results indicated that syllable duration context effects were present across all conditions for both adults and children. However, the adults and children did differ in the 3rd condition, in which both the transition frequency and the transition duration were altered. Thus, children used the dynamic formant transitions differently than adults when transition frequency was varied along with transition duration. These findings show that children have a bias toward formant transitions and indicate that young children of 4-5 years of age attend differently than adults to changes in dynamic cues such as formant transitions, as predicted by the developmental cue weighting shift model.

Unlabelled: The purpose of this study was to assess the effect of phonological neighborhood density on the speech reaction time (SRT) and errors of children who do and do not stutter during a picture-naming task. Participants were nine 3-5-year-old children who stutter (CWS) matched in age and gender to nine children who do not stutter (CWNS). Initial analyses indicated that both CWNS and CWS were significantly faster (i.e., exhibited shorter SRTs) and more accurate on phonologically sparse than phonologically dense words, findings consistent with those found with older children (Newman & German, 2002). Further analyses indicated that talker group differences in receptive language scores weakened these findings. These preliminary findings were taken to suggest that phonological neighborhood density appears to influence the picture-naming speed and accuracy of preschool-aged children., Educational Objectives: The reader will learn about and be able to: (1) recognize the relevance of examining phonological variables in relation to childhood stuttering; and (2) describe the method of measuring speech reaction times and errors during a picture-naming task as a means of assessing linguistic skills.

The purpose of this study was to assess the influence of phonological priming on the speech reaction time (SRT) of children who do (CWS) and who do not (CWNS) stutter during a picture-naming task. Participants were eighteen 3-5-year-old CWS (M = 50.67 months, SD = 11.83 months), matched in age and gender with 18 CWNS (M = 49.44 months, SD = 10.22 months). The picture-naming task required each child to name, one at a time, computer-presented, white-on-black line drawings of common, age-appropriate objects "as quickly as you can" during 3 different conditions: (a) no prime, (b) related prime, and (c) unrelated prime, with naming latency (alternatively referred to as SRT; in milliseconds) as the main dependent variable. Results indicated that all children exhibited faster or shorter SRTs during the related condition compared to the no prime condition. Similarly, SRT was influenced with advancing age for all children, with 5-year-olds exhibiting faster SRTs than 3-year-olds. Furthermore, CWNS, but not CWS, demonstrated a negative correlation between articulatory mastery and SRT. Findings were taken to suggest that phonological priming is a feasible procedure for studying the speech-language planning and production of 3-5-year-old children and that preschool children who stutter, as a group, may have somewhat less well developed articulatory systems than preschool children who do not stutter.

The purpose of this study was to assess anticipatory coarticulation and second formant (F2) transition rate (FTR) of speech production in young children who stutter (CWS) and who do not stutter (CWNS). Fourteen CWS and 14 age- and gender-matched CWNS in three age groups (3-, 4-, and 5-year-olds) participated in a picture-naming task that elicited single-word utterances. The initial consonant-vowel (CV) syllables of these utterances, comprising either bilabial [b m] or alveolar [d n s z] consonants and a number of vowels [i I e epsilon ae u o c aI av],were used for acoustic analysis. To assess coarticulation and speech movement velocity, the F2 onset frequency and F2 vowel target frequency (for coarticulation) and FTR (for speech movement velocity) were computed for each CV syllable and for each participant. Based on these measures, locus equation statistics of slope, y-intercept, and standard error of estimate as well as the FTR were analyzed. Findings revealed a significant main effect for place of articulation and a significantly larger difference in FTR between the two places of articulation for CWNS than for CWS. Findings suggest that the organization of the FTR production for place of articulation may not be as contrastive or refined in CWS as in CWNS, a subtle difficulty in the speed of speech-language production, which may contribute to the disruption of their speech fluency.

The purpose of this study was to determine the role of static, dynamic, and integrated cues for perception in three adult age groups, and to determine whether age has an effect on both consonant and vowel perception, as predicted by the "age-related deficit hypothesis." Eight adult subjects in each of the age ranges of young (ages 20-26), middle aged (ages 52-59), and old (ages 70-76) listened to synthesized syllables composed of combinations of [b d g] and [i u a]. The synthesis parameters included manipulations of the following stimulus variables: formant transition (moving or straight), noise burst (present or absent), and voicing duration (10, 30, or 46 ms). Vowel perception was high across all conditions and there were no significant differences among age groups. Consonant identification showed a definite effect of age. Young and middle-aged adults were significantly better than older adults at identifying consonants from secondary cues only. Older adults relied on the integration of static and dynamic cues to a greater extent than younger and middle-aged listeners for identification of place of articulation of stop consonants. Duration facilitated correct stop-consonant identification in the young and middle-aged groups for the no-burst conditions, but not in the old group. These findings for the duration of stop-consonant transitions indicate reductions in processing speed with age. In general, the results did not support the age-related deficit hypothesis for adult identification of vowels and consonants from dynamic spectral cues.

The purpose of this study was to examine the acoustic characteristics of children's speech and voices that account for listeners' ability to identify gender. In Experiment I, vocal recordings and gross physical measurements of 4-, 8-, 12-, and 16-year olds were taken (10 girls and 10 boys per age group). The speech sample consisted of seven nondiphthongal vowels of American English (/ae/ "had," /E/ "head," /i/ "heed," /I/ "hid," /a/ "hod," /inverted v/ "hud," and /u/ "who'd") produced in the carrier phrase, "Say /hVd/ again." Fundamental frequency (f0) and formant frequencies (F1, F2, F3) were measured from these syllables. In Experiment II, 20 adults rated the syllables produced by the children in Experiment I based on a six-point gender rating scale. The results from these experiments indicate (1) vowel formant frequencies differentiate gender for children as young as four years of age, while formant frequencies and f0 differentiate gender after 12 years of age, (2) the relationship between gross measures of physical size and vocal characteristics is apparent for at least 12- and 16-year olds, and (3) listeners can identify gender from the speech and voice of children as young as four years of age, and with respect to young children, listeners appear to base their gender ratings on vowel formant frequencies. The findings are discussed in relation to the development of gender identity and its perceptual representation in speech and voice.

Measures of monaural temporal processing and binaural sensitivity were obtained from 12 young (mean age = 26.1 years) and 12 elderly (mean age = 70.9 years) adults with clinically normal hearing (pure-tone thresholds < or = 20 dB HL from 250 to 6000 Hz). Monaural temporal processing was measured by gap detection thresholds. Binaural sensitivity was measured by interaural time difference (ITD) thresholds. Gap and ITD thresholds were obtained at three sound levels (4, 8, or 16 dB above individual threshold). Subjects were also tested on two measures of speech perception, a masking level difference (MLD) task, and a syllable identification/discrimination task that included phonemes varying in voice onset time (VOT). Elderly listeners displayed poorer monaural temporal analysis (higher gap detection thresholds) and poorer binaural processing (higher ITD thresholds) at all sound levels. There were significant interactions between age and sound level, indicating that the age difference was larger at lower stimulus levels. Gap detection performance was found to correlate significantly with performance on the ITD task for young, but not elderly adult listeners. Elderly listeners also performed more poorly than younger listeners on both speech measures; however, there was no significant correlation between psychoacoustic and speech measures of temporal processing. Findings suggest that age-related factors other than peripheral hearing loss contribute to temporal processing deficits of elderly listeners.

Recent research on 5- to 11-year-old children's perception of stop consonants and vowels indicates that they can generally identify these sounds with relatively high accuracy from short duration stimulus onsets [Ohde et al., J. Acoust. Soc. Am. 97, 3800-3812 (1995); Ohde et al., J. Acoust. Soc. Am. 100, 3813-3824 (1996)]. The purpose of the current experiments was to determine if younger children, aged 3-4 years, can also recover consonant and vowel features from stimulus onsets. Ten adults, ten 3-year olds, and ten 4-year-olds listened to synthesized syllables composed of combinations of [b d g] and [i u a]. The synthesis parameters included manipulations of the following stimulus variables: formant transition (moving or straight), noise burst (present or absent), and voicing duration (10, 30, or 46 ms). Developmental effects were found for the perception of both stop consonants and vowels. In general, adults identified these sounds at a significantly higher level than children, and perception by 4-year-olds was significantly better than 3-year-olds. A developmental effect of dynamic formant motion was obtained, but it was limited to only the [g] stop consonant. Stimulus duration affected the children's perception of vowels indicating that they may utilize additional auditory information to a much greater extent than adults. The results support the importance of information in stimulus onsets for syllable identification, and developmental changes in sensitivity to these cues for consonant and vowel perception.

The purpose of this study was to assess the perceptual role of brief synthetic consonant-vowel syllables as cues for vowel perception in children and adults. Nine types of consonant-vowel syllables comprised of the stops [b d g] followed by the vowels [i a u] were synthesized. Stimuli were generated with durations of 10, 30, or 46 ms, and with or without formant transition motion. Eight children at each of five age levels (5, 6, 7, 9, and 11 years) and a control group of eight adults were trained to identify each vowel in a three-alternative forced-choice (3AFC) paradigm. The results showed that children and adults extracted vowel information at a generally high level from stimuli as brief as 10 ms. For many stimuli, there was little or no difference between the performance of children and adults. However, developmental effects were observed. First, the accuracy of vowel perception was more influenced by the consonant context for children than for adults. Whereas perception was similar across age levels for stimuli in the alveolar context, the youngest children perceived vowels in the labial and velar contexts at significantly lower levels than adults. Second, children were more affected by variations in stimulus duration than were adults. This finding was particularly prominent for the syllable [ga], where the dependency on duration decreased with age in a nearly linear fashion. These findings are discussed in relation to current hypotheses of vowel perception in adults, and hypotheses of speech perception development.

It has been hypothesized that the acoustic properties within a temporal domain of 10 to 30 ms of boundaries between speech sounds contain significant information on the phonetic features of segments, and that these cues are perceptually integrated by the auditory system [Stevens, Phonetic Linguistics: Essays in Honor of Peter Ladefoged (Academic, London, 1985)]. The purpose of the current research was to examine the effects of stimulus duration adjacent to speech sound boundaries on the perceptual integration of place of articulation of nasals before and after disruption of the abrupt changes in spectra between the murmur and transition. In experiment I, three children, aged 3, 5, and 7 years, and an adult female and male produced consonant-vowel (CV) syllables consisting of [m] and [n] in four vowel contexts, [i ae u a]. Approximately 25-ms segments of the murmur and vowel transition adjacent to the speech sound boundary were digitally removed from these productions. Intervals of silence ranging from 0 to 2000 ms, which can potentially perturb integration processes, were inserted between these segments. The stimuli were then presented to adult listeners for the identification of the nasal. The main findings revealed a consistent decline in identification with gap durations up to 150 ms across speakers and vowel context. However, the adult labial feature was resistant to perceptual change as a function of gap duration. This result appeared to relate to formant transition duration, and not to response bias. In experiment II, stimuli with durations shorter than those in experiment I were further analyzed for adult speakers. The main finding was a quantification of the acoustic segment duration needed for perceptual integration of the murmur and vowel transition. Across both experiments, the results reveal a decline in the identification of both alveolar and labial nasals within a time interval mediated by short-term auditory memory, and that the duration of the acoustic segment needed for perceptual integration is longer for [n] than [m].

Previous research has noted a reduction in perceptual identification performance when the speaker varies from stimulus to stimulus and has interpreted this finding as an effect of a normalization process that compensates for variability in the physical content of the speech signal. The purpose of the present investigation was to examine whether the physical variability introduced by this experimental design can result in general stimulus uncertainty effects that extend beyond the realm of traditional delineations of normalization processes. The stimuli were short segments taken from nasal consonant + vowel syllables produced by 1 male adult, 1 female adult, and 2 children. Segments of 25 and 50 ms duration were edited from the nasal murmur and the onset of the vowel. The stimuli were ordered according to four variability conditions and presented to listeners for place of articulation identification. The results showed that identification was significantly reduced when variability affected either speaker identity or segment type. Further analyses revealed that segment variability impaired perception of all segment types approximately equally, but that the 50-ms vowel segments were selectively spared in the speaker variability condition. These findings indicate that general uncertainty effects should be considered in speech perception experiments, and that dynamic properties of speech are particularly important in the perceptual compensation for speaker variability.

The importance of different acoustic properties for the perception of place of articulation in prevocalic stop consonants was investigated from a developmental perspective. Eight adults and eight children in each of the age groups, 5, 6, 7, 9, and 11 years, listened to synthesized syllables comprised of all combinations of [b d g] and [i a]. The synthesis parameters were adapted from Blumstein and Stevens [J. Acoust. Soc. Am. 67, 648-662 (1980)], and included manipulations of the following stimulus variables: formant transitions (moving or straight), noise burst (present or absent), and voicing duration (10 or 46 ms). Identification performance was high for all age groups across most stimulus types. Formant transition motion generally was not necessary for accurate identification, and there was no difference between age groups in terms of the perceptual weight placed on this cue. Furthermore, the results did not support the salience of duration as a developmental cue to place of articulation. The presence of a burst improved identification for the velar and alveolar places of articulation for all age groups, but was particularly important for the 11-year-olds and adults. These findings indicate that children, by age 5, do not rely on dynamic formant motion any more than adults do, and that the ability to integrate acoustic cues across regions of spectral change shows developmental patterns.

The processes involved in the perception of spectral change between the nasal murmur and the vocalic transition for speakers of different ages were assessed before and after disruption of the variation in spectra between these elements. Three children, aged 3, 5, and 7, and an adult female and male produced consonant-vowel (CV) syllables consisting of either [m] or [n] followed by [i] or [u]. In one condition (spectrally noncontiguous), the acoustic information surrounding the region of spectral change was digitally removed and in another condition (spectrally contiguous) this portion of the signal was retained. In both of these conditions, intervals of silence ranging from 0 to 2000 ms were inserted between 50-ms segments of murmur and vocalic transition. These gap duration conditions were then presented to adult listeners for the identification of the nasal. Across speakers, the results for the spectral contiguous condition support a primary mechanism in the perception of spectral relations that is mediated by processes within short-term auditory memory, but the results for the spectral noncontiguous condition revealed little consistent support for either short-term or long-term memory processes.

The contribution of the nasal murmur and vocalic formant transition to the perception of the [m]-[n] distinction by adult listeners was investigated for speakers of different ages. Children, aged 3, 5, and 7, and an adult female and male produced consonant-vowel (CV) syllables consisting of either [m] or [n] and followed by [i ae u a]. Three productions of each syllable were computer edited into the following segments: (1) full murmur; (2) 50-ms murmur preceding release; (3) 25-ms murmur preceding release; (4) 25-ms murmur preceding release +25-ms transition following release; (5) 25-ms transition following release; (6) 50-ms transition following release; and (7) full transition+vowel. The results indicate that both the murmur and transition provide cues to place of articulation, but that the latter property is more prominent in perception than the former across speaker age. The salience of the murmur and vocalic transition cues was greater for adults than children indicating a developmental progression of the encoding of gestures associated with these properties. Although the simultaneous presence of murmur and vocalic transition cues surrounding the point of spectral discontinuity improved perception of place of articulation across speakers, there was evidence of a developmental progression of this property also. For speakers of all ages, as segment duration decreased, consistent decrements in identification of place of articulation occurred only for transition stimuli. The murmur+transition was the most salient cue supporting the importance of spectral discontinuities and/or relational properties in production and perception particularly in the acquisition of sound features.

The amplitude of frication relative to vowel onset amplitude in the F3 and F5 formant frequency regions was manipulated for the synthetic fricative contrasts /s/-/integral of/ and /s/-/theta/, respectively. The influence of this relative amplitude manipulation on listeners' perception of place of articulation was tested by (1) varying the duration of frication from 30 to 140 ms, (2) pairing the frication noise with different vowels /i a u/, (3) placing formant transitions in conflict with relative amplitude, and (4) holding relative amplitude constant within a continuum while varying formant transitions and the amplitudes of spectral regions where relative amplitude was not manipulated. To determine if listeners were using absolute spectral cues or relative amplitude comparisons between frication and vowel for fricative identification, the frication and vowel were separated by (1) presenting the frication in isolation, and (2) inserting a gap of silence between the frication and vowel. The results showed that relative amplitude was perceived across vowel context and frication duration, and overrode context-dependent formant transition cues. The findings for temporal separations between the frication and vowel suggest that short-term memory processes may dominate the mediation of the relative-amplitude comparison. However, the overall results indicate that relative amplitude is only a component of spectral prominence, which is comprised of a primary frication spectral peak and a secondary frication/vowel peak comparison.

The perception of voicing in final velar stop consonants was investigated by systematically varying vowel duration, change in offset frequency of the final first formant (F1) transition, and rate of frequency change in the final F1 transition for several vowel contexts. Consonant-vowel-consonant (CVC) continua were synthesized for each of three vowels, [i,I,ae], which represent a range of relatively low to relatively high-F1 steady-state values. Subjects responded to the stimuli under both an open- and closed-response condition. Results of the study show that both vowel duration and F1 offset properties influence perception of final consonant voicing, with the salience of the F1 offset property higher for vowels with high-F1 steady-state frequencies than low-F1 steady-state frequencies, and the opposite occurring for the vowel duration property. When F1 onset and offset frequencies were controlled, rate of the F1 transition change had inconsistent and minimal effects on perception of final consonant voicing. Thus the findings suggest that it is the termination value of the F1 offset transition rather than rate and/or duration of frequency change, which cues voicing in final velar stop consonants during the transition period preceding closure.

The purpose of this study was to determine the importance of the vocalic transition relative to other acoustic cues in the perception of both CV and VC syllables. Subjects identified stops, /p, t, k, b, d, g/ and vowels, /i, u, 3/ from the aperiodic, aperiodic + vocalic transition, vocalic transition, and vocalic transition + vowel segments edited from VC and CV syllables. The major findings were as follows: (1) no significant difference was found in consonant identification scores between aperiodic, aperiodic + vocalic transition, and vocalic transition segments in CV syllables compared to those in VC syllables; (2) consonant identifications from vocalic transition + vowel segments in VC syllables were significantly greater than those from vocalic transition + vowel segments in CV syllables; (3) no significant difference was found in vowel identification scores between aperiodic + vocalic transition, vocalic transition + vowel, and vocalic transition segments in CV syllables compared to those in VC syllables; and (4) vowel identifications from aperiodic segments were significantly greater in CV syllables than in VC syllables. The results revealed a significant right-to-left perceptual advantage for both vowels and consonants. The findings for consonant identification emphasize the importance of the temporal order relationship between the vocalic transition and steady-state vowels in the perceptual process.

We have examined the effects of the relative amplitude of the release burst on perception of the place of articulation of utterance-initial voiceless and voiced stop consonants. The amplitude of the burst, which occurs within the first 10-15 ms following consonant release, was systematically varied in 5-dB steps from -10 to +10 dB relative to a "normal" burst amplitude for two labial-to-alveolar synthetic speech continua--one comprising voiceless stops and the other, voiced stops. The distribution of spectral energy in the bursts for the labial and alveolar stops at the ends of the continuum was consistent with the spectrum shapes observed in natural utterances, and intermediate shapes were used for intermediate stimuli on the continuum. The results of identification tests with these stimuli showed that the relative amplitude of the burst significantly affected the perception of the place of articulation of both voiceless and voiced stops, but the effect was greater for the former than the latter. The results are consistent with a view that two basic properties contribute to the labial-alveolar distinction in English. One of these is determined by the time course of the change in amplitude in the high-frequency range (above 2500 Hz) in the few tens of ms following consonantal release, and the other is determined by the frequencies of spectral peaks associated with the second and third formants in relation to the first formant.

Fundamental frequency (F0) and voice onset time (VOT) were measured in utterances containing voiceless aspirated [ph, th, kh], voiceless unaspirated [sp, st, sk], and voiced [b, d, g] stop consonants produced in the context of [i, e, u, o, a] by 8- to 9-year-old subjects. The results revealed that VOT reliably differentiated voiceless aspirated from voiceless unaspirated and voiced stops, whereas F0 significantly contrasted voiced with voiceless aspirated and unaspirated stops, except for the first glottal period, where voiceless unaspirated stops contrasted with the other two categories. Fundamental frequency consistently differentiated vowel height in alveolar and velar stop consonant environments only. In comparing the results of these children and of adults, it was observed that the acoustic correlates of stop consonant voicing and vowel quality were different not only in absolute values, but also in terms of variability. Further analyses suggested that children were more variable in production due to inconsistency in achieving specific targets. The findings also suggest that, of the acoustic correlates of the voicing feature, the primary distinction of VOT is strongly developed by 8-9 years of age, whereas the secondary distinction of F0 is still in an emerging state.

Adult and Child manifolds were generated by synthesizing 5 X 5 matrices of /Cej/ type utterances in which F2 and F3 frequencies were systematically varied. Manifold stimuli were presented to 11 graduate-level speech-language pathology students in two conditions: (a) a rating condition in which stimuli were rated on a 4-point scale between good /r/ and good /w/; and (b) a labeling condition in which stimuli were labeled as "R," "W," "distorted R," or "N" (for none of the previous choices). It was found that (a) stimuli with low F2 and high F3 frequencies were rated 1.0-1.4; those with high F2 and low F3 frequencies were rated 3.6-4.0 were labeled as "R"; (c) none of the Child manifold stimuli were labeled as distorted "R" and one of the Adult manifold stimuli approached a level of identification that approached the percentage of identification for "R" and "W"; and (d) rating and labeling tasks were performed with a high degree of reliability.

The purpose of this study was to determine if children who misarticulate (r) differ from normal children and adults in the perception of sound features that are produced correctly and incorrectly. Children with normal articulation, children who produced (r) misarticulations, and adults listened to synthesized child and adult (r-w) continua in two separate sessions, and to an adult (b-w) control continuum in one session. Perception was evaluated on the basis of measures of phonetic boundary location and the consistency of response to each stimulus in a continuum. The (r)-misarticulating children were found to be significantly less consistent than child and adult controls in responding to the (r-w) stimuli. Moreover, consistency scores were significantly higher for the adult continuum than for the child continuum. The performance of children was different from that of adults. Due to inconsistent performance, boundaries could not be computed for (r)-misarticulating children, but it was found that the boundaries for children in the control group were closer to the (r)-end of the continuum than those for adults. In the case of the (b-w) continuum, it was found that (r)-misarticulating children were significantly less consistent than adults. The phonetic boundaries of children were significantly closer to the (b)-end of the continuum than the boundary for adults. Thus, the results reveal that variability in stimulus response was influenced primarily by the productive ability of the subjects, whereas differences in stimulus categorization were influenced by the age of the subjects. The perceptual variability was most clearly reflected by responses to stimuli produced incorrectly, whereas categorization differences extended to sounds produced correctly.

The purpose of this study was to reexamine the factors leading to stop-consonant perception for consonant-vowel (CV) stimuli with just two formants over a range of vowels, under both an open- and closed-response condition. Five two-formant CV stimulus continua were synthesized, each covering a range of second-formant (F2) starting frequencies, for vowels corresponding roughly to [i,I,ae,u,a]. In addition, for the [I] and [a] continua, the duration of the first-formant (F1) transition was systematically varied. Three main findings emerged. First, criterion-level labial and alveolar responses were obtained for those stimuli with substantial F2 transitions. Second, for some stimuli, increases in the duration of the F1 transition increased velar responses to criterion level. Third, the response paradigm had a substantial influence on stop-consonant perception across all vowel continua. The results support a model of stop-consonant perception that includes spectral and time-varying spectral properties as integral components of analysis.

Important issues in selective adaptation research concern the relative contribution of response related (perceptual) and stimulus related (acoustic) effects of the adaptor in the adaptive process. Two response related issues pertain to the effects of the adaptor percept and verbal transformations on adaptation. This investigation systematically examined perceptual and acoustic contributions of the adaptor on the adaptation of the voicing feature. Subjects rated the degree of voicing/voicelessness of end-point VOT adaptors, i.e., 5- and 55-ms VOT, and an acoustically neutral adaptor, i.e., 25-ms VOT, during periods of repetitions. The number of adaptor repetitions during each of ten trials was either 5, 32, or 95, and the intensity of the adapting stimulus was either 50, 70, or 90 dB SPL. The major findings were as follows: (1) No significant correlations were found between ratings of voicing percept of the adaptor and magnitude of boundary shift; (2) Increases in repetitions and relative intensity level of end-point adaptors produced significantly greater phonetic boundary shifts and generally greater affects on ratings of test stimuli; and (3) The end-point adaptors produced significant shifts in rating of boundary and nonboundary stimuli. The findings indicate that neigher the adaptor percept or verbal transformations affected the magnitude of adaptation. These results and those for acoustic parameters strongly suggest an acoustic as opposed to a phonetic basis of adaptation of the voicing feature. Furthermore, the effects of end-point adaptors on boundary and nonboundary stimuli support the generalized change in feature sensitivity assumed by a fatigue model of adaptation.

The purpose of this study was to investigate the perception of transformations by varying the voice onset time (VOT) of the repeating stimulus, its repetition number, and intensity level. Fifteen subjects rated the 5-, 25-, and 55-ms VOT stimuli during periods of repetitions so that transformations could be identified according to their place and voicing characteristics. The number of stimulus repetitions was 5, 32, or 95, and the sound-pressure level of the repeating stimulus was 50, 70, or 90 dB. The major findings were as follows (1) The 90-dB level condition produced significantly more transformations than either the 50- or 70-dB conditions for the 55-ms stimulus only; (2) A significant difference in number of transformations was obtained for each paired copmparison of the 55-ms stimulus, but only between the 5-, 32-, and 95- repetition pairs for the 5 and 25 ms stimuli; and (3) Significant correlations were obtained between the voiceless and alveolar features of transformations for the 55-ms stimulus, and between the voiced, alveolar, and velar features of transformations for the 5- and 25-ms stimuli. The findings support a transformation process sensitive to voicing and place cues and a peripheral component of transformations.

Fundamental frequency (F0) and voice onset time (VOT) were measured in utterances containing voiceless aspirated /ph,th,kh/, voiceless unaspirated /sp,st,sk/, and voiced /b,d,g/ stop consonants. Although VOT was very similar for voiceless unaspirated and voiced stops, F0 contours were nearly identical for voiceless unaspirated and voiceless aspirated stops, and both types of voiceless stops were associated with significantly higher F0 values than were voiced stops. The F0 contours in all context were generally falling; the data do not support a simple rise-fall dichotomy in F0 at voicing onset as an invariant acoustic correlate of the voicing feature. The variations in F0 as a function of voicing appear to be best accounted for by vocal cord tension rather than aerodynamic influences. Moreover, the results are consistent with physiological data showing that the position of the hyoid bone and the height of the larynx influence the absolute value of F0.

In a recent article in the Journal [L. C. W. Pols and M. E. H. Schouten, J. Acoust. Soc. Am. 64, 1333-1337 (1978)], it was concluded that perception experiments which present CV syllables with the consonant bursts deleted invoke a "click sensation" and that this sensation has a deleterious affect on the perception of the consonants. In order to directly assess the "click sensation" hypothesis, a computer-based speech editing system was used which smooths onsets and offsets of stimuli and therefore eliminates the possibility of an acoustic click. Subjects identified voiced and voiceless stops from vocalic transition + vowel stimuli edited from CV and VC syllables. The findings were as follows: (1) Consonant identification from vocalic transition + vowel segments in VC syllables was significantly greater than that from vocalic transition + vowel segments in CV syllables; and (2) The superiority of the scores for VC vocalic transition + vowel segment was found for both voiced and voiceless stops, but it was not as great for voiced stops. Although there are differences in magnitude of findings between this study and those which employed other deletion techniques, the reliability and direction of the results were similar. The results do not support the "click sensation"hypothesis and suggest that other mechanisms must account for differences between CV and VC syllables in the perception of sound segments.

The purpose of this study was to assess the extent to which listeners can perceive intraphonemic differences. In Experiment 1, subjects identified synthesized acoustic tokens of child-like speech that varied in second and third formant (F2 and F3) onset frequencies as (w), (r), or distorted (r) in two conditions: (a) with and without feedback of the group response choices, and (b) before and after training to identify the best examples of (w), (r), and distorted (r) based on their identification in the first condition. The results were: (a) some subjects consistently identified distorted (r) above criterion, and (b) feedback was more effective in increasing distorted (r) identification than was training. In Experiment 2, the same subjects participated in discrimination tasks using stimuli from a synthesized child (w-r) continuum that varied in F2 and F3 onsets and from a synthesized adult (t-d) continuum that varied in preconsonantal vowel duration. The results were: (a) perception was not categorical for both continua, (b) little relation was found between distorted-(r) identification and measures of (w-r) discrimination, and (c) a high and significant correlation was found between identification of distorted (r) and within-(d) discrimination. In Experiment 3, different subjects identified the child manifold stimuli and discriminated stimuli in a synthesized child (w-r) continuum and in a synthesized adult (t-d) continuum. The results were: (a) neither (w-r) or (t-d) perception was categorical although the former came closer than the latter in terms of individual subject performance, (b) there was a high and significant correlation between distorted-(r) identification and within-(r) discrimination of (w-r) stimuli, and (c) there were high and significant correlations between distorted-(r) identification and mean, cross-category boundary, and within-(t) discrimination of (t-d) stimuli.

The purpose of this study was to assess the use of psychophysical transformations for analyzing the differentiation of /w/ and /r/ sounds of children and adults. Stimuli from Adult and Child manifolds, consisting of 25 synthesized /Cej/-type utterances with different F2 and F3 onset frequencies, were presented in random order to eight naive subjects. Subjects rated the stimuli on a four-point scale between good /r/ and good /w/. Correlations between mel transformations and Bark transformations of the F3-F2 differences among the stimuli and their percent /r/ responses were close to or greater than .90. Predictions of percent /r/ responses derived from regression analyses based on mel transformations and Bark transformations of F3-F2 differences among stimuli indicated that some sounds identified as /w/ for /r/ substitutions could be differentiated from /w/ sounds. The category boundaries between /r/ and /w/ were estimated to be 5.0 Bark for adult stimuli and 5.7 Bark for child stimuli.

Identification of place of articulation in the synthesized syllables /bi/, /di/, and /gi/ was examined in three groups of listeners: (a) normal hearers, (b) subjects with high-frequency sensorineural hearing loss, and (c) normally hearing subjects listening in noise. Stimuli with an appropriate second formant (F2) transition (moving-F2 stimuli) were compared with stimuli in which F2 was constant (straight-F2 stimuli) to examine the importance of the F2 transition in stop-consonant perception. For straight-F2 stimuli, burst spectrum and F2 frequency were appropriate for the syllable involved. Syllable duration also was a variable, with formant durations of 10, 19, 28, and 44 ms employed. All subjects' identification performance improved as stimulus duration increased. The groups were equivalent in terms of their identification of /di/ and /gi/ syllables, whereas the hearing-impaired and noise-masked normal listeners showed impaired performance for /bi/, particularly for the straight-F2 version. No difference in performance among groups was seen for /di/ and /gi/ stimuli for moving-F2 and straight-F2 versions. Second-formant frequency discrimination measures suggested that subjects' discrimination abilities were not acute enough to take advantage of the formant transition in the /di/ and /gi/ stimuli.

The purpose of this research was to assess the perceptual effects of a range of second (F2) and third (F3) formant transition rates that occur naturally in the production of /w/ and /r/ by children and adults. Synthesized CV continua that varied in the second (F2) and third (F3) formant onset frequencies between values appropriate for /w/ and /r/ were used as stimuli. Subjects participated in four experimental conditions that involved changing the rate of transition of either F2 or F3 by varying the duration of the transition between the glide onset and an /eI/ vowel nucleus for child and adult stimuli. In each condition, the transition rates of the /w/-endpoint stimulus, the /r/-endpoint stimulus, and at least one of the midpoint stimuli were varied across values appropriate for /w/ and /r/. Mean ratings of the stimuli were compared to test the predictions that /w/ perception increases with increased F2 transition rate and increases with decreased F3 transition rate. The results were as follows: (a) one of the 10 comparisons for the child F2 stimuli was significant, but it involved a change opposite to the predicted direction; (b) four of the six comparisons for the child F3 stimuli were significant, but they involved changes opposite to the predicted direction; (c) 14 comparisons of adult F2 stimuli were significant, but 12 of these 14 comparisons involved changes opposite to the predicted direction; and (d) four of the six comparisons for the adult F3 stimuli were significant, but none of them involved changes in the predicted direction. Only one of all the comparisons involved a significant change in rating between the /w/ and /r/ categories.