Perception Of Vowel Duration Research Articles

The effect of linguistic experience on perceived vowel duration: Evidence from Taiwan Mandarin speakers

Perceived vowel duration is known to be influenced by many factors, including f0 height/movement and ones’ native phonological system. Using multiple experimental paradigms, this study examined whether native tonal representations and phonetic knowledge of duration associated with different lexical tones may further shape the ways in which vowel duration is perceived. In a perception experiment, Taiwan Mandarin and Korean listeners rated the duration of duration-controlled CV syllables carrying one of the four lexical tones in Mandarin or a reduced T3half (X21). The results showed that perceived vowel duration by Korean listeners, the control group, reflected general perceptual biases: contour tones were rated as longer than level tones, and high-f0 tones were rated as longer than low-f0 tones. Taiwan Mandarin listeners, on the other hand, overestimated the duration of vowels carrying T3 (X214) and T3half, despite their short phonetic duration in Taiwan Mandarin, indicating the significance of the canonical representation of the complex T3 contour. A spontaneous imitation experiment further supported the canonicity effect: T3half was again hyperarticulated, produced as longer and with similar f0 trajectories as T3full, based on its phonological association to T3. Taken together, the findings of the present study suggest that the perception of vowel duration is guided by higher-order phonological knowledge from speakers’ linguistic experience as well as by general perceptual biases.

A perceptual pathway for voicing-conditioned vowel duration

When codas and vowels are cross-spliced, vowels originally produced with voiced codas are perceived as longer than vowels of the same duration produced with voiceless codas. The spliced coda has the opposite effect: Vowels presented with voiced codas are perceived as shorter. To explain what characteristics make vowels produced with voiced codas sound longer than vowels produced with voiceless codas, four experiments tested how acoustic correlates of voicing affect English speakers’ perception of vowel duration. Vowels were manipulated in a ten-step duration continuum, and listeners categorized each vowel as ‘long’ or ‘short.’ Study 1 tested effects of vowel height categories (/æ, ε, ɪ/) and within-category F1. Study 2 tested effects of intensity contour. Study 3 tested effects of spectral tilt. Perceived vowel duration increased with vowel height and rising intensity. Perceived vowel duration decreased with falling intensity and with higher spectral tilt. There was no effect of within-category F1. Study 4 confirmed that the effect of the original coda environment is not specific to English stimuli. The effects of spectral tilt and intensity contour on perceived duration provide a possible perceptual pathway for the development of voicing-conditioned vowel duration; coda voicing influences these characteristics and they in turn influence perceived vowel duration.

Phrase-final lengthening modulates listeners' perception of vowel duration as a cue to coda stop voicing.

The present study addresses how listeners may be sensitive to temporal regularities associated with prosody in their perception of durational segmental cues. Specifically, this study tests whether expectations about phrase-final lengthening mediate listeners' categorization of a "coat"∼"code" vowel duration continuum, where vowel duration cues stop voicing. Prosodic position of the target was manipulated such that it was either medial, or final in a carrier phrase. Results indicate that this prosodic manipulation influences categorization such that listeners effectively require longer vowel duration for a "code" response when the target is phrase-final, suggesting that prosodic patterns can modulate listeners' processing of temporal cues.

Influence of coda stop features on perceived vowel duration

Four experiments tested what cues contribute to English speakers’ perception of vowel duration. Listeners categorized the duration of vowels as ‘long’ or ‘short’ for stimuli produced with voiced, voiceless, breathy voiced, or voiceless aspirated stop codas. Listeners demonstrated a strong ability to perceive vowel duration, though perception was continuous rather than categorical. There were several interacting factors influencing perceived vowel duration, based on expectations set by the presence of particular codas and also acoustic effects of the coda on the vowel. When the coda was removed, vowels that had been produced before voiced codas were perceived as longer than vowels produced before voiceless codas, though they exhibited the opposite effect when codas were present. Vowels were also perceived as longer when produced before breathy voiced stops, regardless of whether or not the stop was present. The steeper f0 falls associated with voiced codas within these stimuli likely contributed to the longer perceived duration of vowels from this environment; manipulating f0 contours eliminated effects of the original coda on perceived vowel duration. The effects of the production environment on perceived vowel duration suggest a possible perceptual pathway for the voicing effect on vowel duration.

Coda and tonal effects on perceived vowel duration

The shape of pitch contours has been shown to have an influence on the perceived vowel duration in that listeners tend to perceive vowels as shorter when they are produced as longer (compensatory listening strategy, Guessenhoven & Zhou, 2013). This study further investigates if the syllable structure allowed in one's native language and the frequency of tone types also affect perceived duration. An AX perceptual experiment was conducted using disyllabic structures (i.e., mepVC) in which the target vowel ([a] and [i]) in four duration steps (180, 210, 240, 270ms) and 5 pitch contours (LL, HH, HL, LH, HLH) and 7 codas ([p], [t], [k], [m], [n], [ŋ], [∅]) are embedded in the second syllable, to be compared with an anchor stimulus with a fixed vowel duration (225ms) and pitch (195Hz). Taiwanese Southern Min speakers, whose native language allows obstruent codas, and Mandarin speakers, whose native language only allows nasal codas, were recruited to participate in the experiment in which they were told to listen to pairs of meaningless words and asked to compare the durations of the second vowels and rate them on a 7-point scale. The results showed that perceived duration cannot be solely explained by compensatory listening strategy. Instead, tone inventory, tone frequency and the syllable structure allowed in the native language all contribute to the perceived vowel duration.

Speech perception and lexical effects in specific language impairment

Using an identification task, we examined lexical effects on the perception of vowel duration as a cue to final consonant voicing in 12 children with specific language impairment (SLI) and 13 age-matched (6;6–9;6) peers with typical language development (TLD). Naturally recorded CV/t/sets [word–word (WW), nonword–nonword (NN), word–nonword (WN) and nonword–word (NW)] were edited to create four 12-step continua. Both groups used duration as an identification cue but it was a weaker cue for children with SLI. For NN, WN and NW continua, children with SLI demonstrated certainty at shorter vowel durations than their TLD peers. Except for the WN continuum, children with SLI demonstrated category boundaries at shorter vowel durations. Both groups exhibited lexical effects, but they were stronger in the SLI group. Performance on the WW continuum indicated adequate perception of fine-grained duration differences. Strong lexical effects indicated reliance on familiar words in speech perception.

Interactions of fundamental frequency contour and perceived duration in Norwegian.

This study investigates the influence of fundamental frequency (F0) contour on perceived vowel duration in Norwegian. In the first of four experiments, a falling vs. flat contour in short vs. long vowels in isolated monosyllables was shown to cause a perceptual lengthening of the vowel. Contrary to the expectations, embedding the monosyllables sentence-medially in experiment 2 did not turn the lengthening into a shortening effect. Also unexpectedly, a rising vs. flat contour did not influence perceived duration in monosyllables (experiment 3). Experiment 4 focused on falling as well as rising contours in disyllabic test words. Here, too, a lengthening effect was found only for a falling pattern. In parallel with experiment 2, the presence of the test word's second syllable did not turn perceptual lengthening into perceptual shortening. Comparison of the present results with data previously reported for German leads to the conclusion that the interaction of F0 contour and perceived vowel duration is language-specific and cannot be explained by assuming a universal psychophysical mechanism.

Does dynamic F0 increase perceived duration? New light on an old issue

This paper investigates the influence of fundamental frequency (F 0 ) pattern on the perception of vowel duration. Three series of experiments were conducted. The first series examined dynamic vs . flat F 0 contours in short vs . long vowels in German disyllabic words. The data showed that, contrary to the established opinion, a dynamic vs . a flat F 0 contour shortens rather than lengthens perceived duration. This effect turned out to be independent of the character of the post-vocalic consonant, the position of the test word in the sentence and the presence or absence of a carrier phrase. The second series investigated perceived vowel duration in isolated monosyllabic words as opposed to disyllables and sentence-embedded monosyllables. The results revealed that the classical perceptual lengthening effect due to a changing F 0 is only present when using isolated monosyllables. As soon as phonetically voiced stretches of speech are added, the lengthening effect is reversed. The third part dealt with the interaction of F 0 and the perception of fortis/lenis plosives in disyllabic words. Here, the usual bias towards more lenis percepts due to a dynamic F 0 pattern was replicated. Previous investigations explain this phenomenon by a subjectively longer vowel, mediated by a dynamic F 0 contour. In view of the present results on vowel quantity perception this explanation seems no longer tenable. Instead, a production-perception link is assumed. In the light of all the present results, it must be concluded that the varying influences of F 0 on the perception of duration cannot be traced back to a single, universal mechanism.

Production and perception of vowel duration as a cue to the word‐final English /t/‐/d/ contrast by native and Chinese subjects

Vowel duration was measured in seven minimally paired English words such as beat‐bead and bat‐bad as spoken by native English (NE) subjects and four groups of Chinese subjects (ten per group). The Chinese subjects were either relatively inexperienced (MA, TA) or experienced (TB) adult learners of English, or else had learned English as an L2 before the age of 12 years (TC). The early learners in TC closely resembled the NE speakers in making vowels much longer before /d/ than /t/. The inexperienced adult learners (MA, TA) produced a voicing effect, but one that was far smaller than that of the subjects in NE and TC. The experienced adult learners in TB produced a significantly larger voicing effect than the inexperienced subjects in TA and MA, but their effect was also smaller than that of the subjects in NE and TC. Sensitivity to vowel duration as a perceptual cue to the English /t/‐/d/ contrast was investigated in three ways. The subjects identified the members of natural continua in which vowel duration was varied by deleting glottal pulses. One continuum ranged from bead to beat, the other from bad to bat. The subjects imitated the members of both continua, and also chose which members of the continua represented the best exemplars of bead, beat, bad, and bat. As expected from the production data, the early learners in TC resembled the NE speakers perceptually, whereas the inexperienced adult learners (MA, TA) showed little evidence of perceptual sensitivity to vowel duration. Some experienced adult learners in group TB, on the other hand, were perceptually sensitive to the vowel duration cue. The relationship between their production and perception will be discussed.

Speech feature recognition by profoundly hearing impaired children using a multiple-channel electrotactile speech processor and aided residual hearing

A group of prelinguistically hearing impaired children, between 7 and 11 years of age, were trained in the perception of vowel duration and place, the fricative /s/, and manner of articulation (/m/ vs /b/ and /s/ vs /t/) distinctions, using information provided by a multiple-channel electrotactile aid (Tickle Talker), and through aided hearing. Training was provided in the tactile-plus-aided hearing (TA) and tactile (T) conditions. Speech feature recognition tests were conducted in the TA, T, and aided hearing (A) conditions, during pretraining, training, and post-training phases. Test scores in the TA and T conditions were significantly greater than scores in the A condition for all tests, suggesting that perception of these features was improved when the tactile aid was worn. Test scores in the training and post-training phases were significantly greater than in the pretraining phase, suggesting that the training provided was responsible for the improvement in feature perception. Statistical analyses demonstrated a significant interaction between the main effects of condition and phase, suggesting that training improved perception in the TA and T conditions, but not in the A condition. Post-training and training test scores were similar suggesting that the perceptual skills acquired during training were retained after the removal of training. Recognition of trained features improved for trained, as well as for untrained words.

The contribution of vowel duration, F0 contour, and frication duration as cues to the /juz/-/jus/ distinction.

A model was quantified to describe the integration of vowel duration, fricative duration, and fundamental frequency (F0) contour as cues to final position fricatives differing in voicing. The basic assumptions are that perceived vowel duration and perceived frication duration are cues to the identity of final position fricatives and that both F0 contour and vowel duration influence perceived vowel duration. Binary choice and rating responses to synthetic stimuli varying independently along the three dimensions were collected. The results were consistent with the assumption that F0 contour operates by modifying perceived vowel duration, which is a direct cue. Unfortunately, the nature of the modification appears to be very similar in form to that which results from the integration of two independent cues in syllable identification. Therefore, the results do not allow a rejection of the idea that the perception of F0 contour may directly cue the identity of final position fricatives.

Temporal course of perceived vowel duration.

The current study explored the temporal course of the perception of vowel duration. A backward recognition masking paradigm was employed in which the subject was to determine which of two target vowels, differing only in duration, was presented on a given trial. The target was followed, after a variable silent intervowel interval, by a masking vowel having one of three possible durations. Subjects were instructed either to identify the long vowel as /i/ and the short vowel as /I/, or were told that the targets were nonsense sounds they were to identify as long or short. For both instruction conditions, identification of the long target improved consistently with increases in the intervowel interval, whereas identification of the short target was equally accurate at the long and the short intervals. Identification of the long target vowel was most accurate when followed by a long masking vowel, whereas identification of the short target vowel was most accurate when followed by a short masking vowel. An information-processing model provided a good description of the quantitative results.

Perception of vowel duration

Lehiste and Pisoni have independently shown that the perception of vowel duration is influenced by the F0 pattern that accompanies the vowel. Here we report some related results. Sixteen subjects are asked to judge the relative duration of pairs of synthesized stimuli. The stimulus pairs are made up of the vowels /i/, /a/, /ai/, and nonspeech, where nonspeech is a single formant at 1500 Hz. The F0 patterns are: level = 120 Hz, rising = 105–135 Hz, and falling = 135 to 105 Hz. The durations are 220, 240, 260, and 280 msec. The orthogonal combination of these factors makes up a total of 512 stimulus pairs. In comparing duration judgements of stimuli of rising (R), falling (F), and level (L) F0's, we found that the following relation obtains: R > F > L, where “>” denotes “perceived as having greater duration.” This relation holds to the same extent for both speech and nonspeech stimuli. There is no signficant difference in the perceived duration between /i/ and /ai/. The most consistent effect, found also earlier in a pilot experiment we performed with 58 subjects, is that /i/ is heard as longer than /a/, in a ratio of 60% : 40%. Since /i/ is normally shorter than /a/ in natural speech, we posit a compensation mechanism mediating between perception and production that is responsible for this negative correlation between vowel height and duration. It is interesting to note that although the processes of duration judgment and pitch judgement (cf. the abstract by Chuang and Wang) are different, they seem to share a common compensation mechanism between production and perception. [Work supported by NSF Grant No. BNS 76-00017-Wang-2/78J34.2.]

Fundamental frequency and perceived vowel duration

What is the relationship between variations in fundamental frequency and perceived duration? At the last meeting of the Society, Prof. Lehiste presented some data dealing with this question. Basically, she found that when listeners are asked to judge the duration of pairs of vowels of equal duration they typically judge the first member of the pair as longer than the second. However, when the second member of the pair contained some variation in FO, listeners perceived it as longer than the first stimulus. In this paper we present the results of two experiments that bear on the general questions raised by Prof. Lehiste's findings. Subjects were presented with all possible pairs of synthetic vowels which varied in duration (160, 200, 240 msec) and fundamental frequency (falling: 200–90 Hz; level: 145 Hz; or rising: 90–200 Hz). They were asked to judge which vowel was longer. The results showed that, in general, vowels containing either a rise or a fall in fundamental frequency were perceived as longer than the corresponding vowels with level fundamentals. These findings were true regardless of the order of presentation of the pair of vowels. The results will be discussed in terms of the interaction between segmental and suprasegmental cues in speech perception. [Research supported by NINCDS Grants NS-12179-01 and NS-07040-01.]

Perception of vowel duration in sentence contexts

The duration of a word such as “deal” ranges from about 310 msec in phrase-final positions in a sentence to as little as 160 msec when used in the phrase “dealer's choice.” A magnitude estimation technique has been used to quantify the expected duration and perceptual tolerance limits for the syllable “deal” in different spoken sentences, where one or more pitch periods of the vowel have been removed or duplicated. Results indicate that listeners adjust their expectations of vowel duration depending on the syntactic position of the vowel in the sentence and the syllable position of the vowel in a word. Thus, the longer durations for phrase-final syllables that were observed previously by one of the authors are part of an English listener's perceptual scheme.