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Perception of anticipatory coarticulation for selected English consonants
Journal of Phonetics (1977) 5, 313-316
Perception of anticipatory coarticulation for selected English consonants Z. S. Bond School of Hearing and Speech Sciences, Ohio University, Athens, Ohio 45701, U.S.A. Received 28th September 1976
Abstract:
This study attempted to determine whether the spectral information contained in a vowel segment excerpted from a eve sequence contained sufficient information to enable listeners to identify the final consonant from the set /1, n, d, r/. Even though such excerpted vowel segments show shifts in identification patterns conditioned by the following consonant, this spectral information is apparently not adequate to enable subjects to predict the consonant.
Introduction In several studies concerning the perceptual effects of coarticulation, it has been found that anticipatory ("forward") coarticulation effects are fairly noticeable; in particular, it seems that a vowel carries considerable information concerning the identity of the following consonant. Ali, Gallagher, Goldstein & Daniloff (1971) report that when both the final consonant and the transition in eve or evve utterances is eliminated, subjects can still predict whether the final consonant was nasal or non-nasal. Kuehn & Moll (1972) report that nasals and fricatives (with the exception of fsf and /z/) can be identified at better than chance expectation when only the transition to the ev syllable is presented at the end of the carrier phrase "had a (eV)". Progressive ("backward") coarticulation appears to be much less identifiable perceptually. Grimm ( 1966) investigated the identifiability of ev syllables with various portions of the initial consonant removed. He found that subjects' responses were essentially random until at least a portion of the consonant was included in the test stimulus. Furthermore, the perceptual effects of coarticulation do not seem to extend to vowels. Lehiste & Shockey (1972) report that the identity of deleted vowels in vev sequences can not be predicted from the ve or ev sequence remaining, after the original sequence is cut in two during the stop closure. Thus, although the data are far from complete, it seems that the identity of consonants is at least in part encoded in the preceding vowel, but that in other types of sequences, the perceptual effect of coarticulation is negligible. In these studies investigating the perceptual correlates of anticipatory coarticulation, subjects have been presented with an utterance of at least a syllable. However, the final consonant can affect the structure of a syllable in more than one way. In particular, the effect can be predominantly spectral, as in the case of the nasalization of a vowel preceding a nasal consonant, or the effect can be predominantly temporal , as in the lengthening of vowels preceding voiced obstruents. The studies of the perceptual effects of anticipatory coarticulation certainly establish that coarticulation cues can be employed to identify deleted consonants ; however, the exact nature of the cues which subjects are using to make the identification is not specified.
314
Z. S. Bond
If vowel segments are excerpted from the vocalic portion of naturally occurring CVC syllables, the formant structure of the vowel segments and the consequ ent identification patterns will be different, depending on the following conso nant (Bond , 1976a, b). In other words, the coarticulation effects of at least some consonants affect the identification patterns of vowels when all but spectral cues of vowel and conso nant id entity are eliminated. An experiment was conducted to determine if these spectral cues are sufficient to enable subjects to predict the consonantal environment from which the vowel was excerpted . Method
Stimuli The four English vowels, /i, E, a , u j, which can be followed by the four consonants / n, I, d, r j were selected for study. Sixteen CVC syllables were constructed. The first consonant of the syllable was /h/, followed by each of the four vowels in combination with each of the four fin al consonants. Two male speakers of midwestern American English recorded the sequences under standard recording conditions. One pitch period was excerpted from each vowel. Using a PDP-1 computer, the analog signal of each word was digitized at 25 K samples/sand displayed on the CRT. One pitch period was selected and excerpted from approximately the mid-point of each vowel. The pitch period was stored for later recall and recording through a digital-to-analog converter. The tape which was used to test subjects was assembled from the excerpted pitch periods. For each stimulus item, 10 iterations of one pitch period were produced without pauses so that each test item was approximately 100 ms in duration . The listening tape consisted of three repetitions of four vowels from four phonetic contexts as produced by two speakers, for a total of 96 test item·s, presented in random order. The interstimulus interval was approximately 5 s. In several respects, stimuli created by this procedure are unnatural : the onset and offset of the vowel is abrupt ; the fundamental frequency is constant ; neither duration nor amplitude vary as in natural speech ; and any spectral changes are eliminated. On the other hand , the procedure serves to eliminate all but spectral cues for the context identification task, and thus makes it possible to assess the perceptual effects of spectral changes due to coarticulation quite directly. Furthermore, vowel tokens created by this procedure have been found to provide adequate spectral information for identification, yet also to be affected , in terms of identification patterns, by the following consonant (Bond, 1976a, b) .
Subjects Two groups of subjects were tested. The fi rst group, 12 undergraduate students at the University of Dayton, Dayton, Ohio, with no training in phonetics, were paid for their participation in the experiment. The second group, 14 undergraduate students enrolled in a phonetics course at Ohio University, Athens, Ohio, were given credit towards completion of course requirements for participation in the experiment. Testing procedure The testing procedure for both groups of subjects was identical. Subjects were instructed to listen to each test item very carefully, and to decide (or guess) if the vowel had been
Anticipatory coarticulation for English consonants
315
followed by /n/, /1/, /d/ or jrf. The listening tape was presented over earphones. Subjects recorded their decisions for each item on a prepared answer sheet. 100 .---------------------,-------------------, Context I II
Context l r I
u
'"
8 c
'"u
&!
Figure 1
The percent correct identification of the final consonant is given for each consonant (in the four quadrants) and vowel tested. The performance of the phonetically experienced subjects is represented by the dark bars; the performance of the phonetically untrained subjects is represented by the light bars.
Results and discussion
The per cent correct identification of each consonant, from the coarticulatory information contained in the vowel, is summarized in Fig. I, for both groups of subjects and for each vowel and consonant tested. It is apparent that for some combinations of vowels and final consonants, subjects were correct in identifying the consonant at better than chance expectation. However, for other vowel-consonant sequences, there was an equally strong tendency to respond with some other consonant than the correct. Overall performance was essentially at chance: 25% correct responses for the phonetically trained subjects and 26 % correct responses for the phonetically untrained subjects. Therefore, although for a few sequences of vowels and consonants, the subjects appeared to be able to guess the missing consonant, perhaps more emphasis should be placed on the over-all performance scores: given the methodology employed in this experiment it appears that the spectral information contained in one excerpted pitch period is not sufficient to enable subjects to identify the following consonant. The research reported in this paper was sponsored in part by the Neurophysiology Branch of the Aerospace Medical Research Laboratory, Aerospace Medical Division, Air Force Systems Command , Wright- Patterson Air Force Base, Ohio, 45433, and supported in part by a research associateship from National Research Council. The voluntary informed consent of the subjects used in this research was obtained as required by Air Force Regulation 80- 33. This paper has been identified by Aerospace Medical Research Laboratory as AMRL-TR-76-77.
References Ali, Latif, Gallagher, Tanya, Goldstein, Jeffrey, & Daniloff, Raymond (1971). Perception of coarticulated nasality. Journal of the Acoustical Society of America 49, 538-40. Bond, Z . S. (l976a) . Identification of vowels excerpted from neutral and nasal context. Journal of the Acoustical Society of America 59, 1229-32. Bond, z. S. (1976b). Identification of vowels excerpted from /1/ and /r/ contexts. Journal of the Acoustical Society of America 60, 906-10.
316
Z. S. Bond
Grimm, W. A. (1966). Perception of segments of English-spoken consonant-vowel syllables. Journal of the Acoustical Society of America 40, 1454-61. Kuehn, David P. & Moll, Kenneth L. (1972). Perceptual effects of forward coarticulation. Journal of Speech and Hearing Research 15, 654-64. Lehiste, lise and Shockey, Linda (1972). On the perception of coarticulation effects in English VCV syllables. Journal of Speech and Hearing Research 15, 500-506.
Perception of anticipatory coarticulation for selected English consonants Z. S. Bond School of Hearing and Speech Sciences, Ohio University, Athens, Ohio 45701, U.S.A. Received 28th September 1976
Abstract:
This study attempted to determine whether the spectral information contained in a vowel segment excerpted from a eve sequence contained sufficient information to enable listeners to identify the final consonant from the set /1, n, d, r/. Even though such excerpted vowel segments show shifts in identification patterns conditioned by the following consonant, this spectral information is apparently not adequate to enable subjects to predict the consonant.
Introduction In several studies concerning the perceptual effects of coarticulation, it has been found that anticipatory ("forward") coarticulation effects are fairly noticeable; in particular, it seems that a vowel carries considerable information concerning the identity of the following consonant. Ali, Gallagher, Goldstein & Daniloff (1971) report that when both the final consonant and the transition in eve or evve utterances is eliminated, subjects can still predict whether the final consonant was nasal or non-nasal. Kuehn & Moll (1972) report that nasals and fricatives (with the exception of fsf and /z/) can be identified at better than chance expectation when only the transition to the ev syllable is presented at the end of the carrier phrase "had a (eV)". Progressive ("backward") coarticulation appears to be much less identifiable perceptually. Grimm ( 1966) investigated the identifiability of ev syllables with various portions of the initial consonant removed. He found that subjects' responses were essentially random until at least a portion of the consonant was included in the test stimulus. Furthermore, the perceptual effects of coarticulation do not seem to extend to vowels. Lehiste & Shockey (1972) report that the identity of deleted vowels in vev sequences can not be predicted from the ve or ev sequence remaining, after the original sequence is cut in two during the stop closure. Thus, although the data are far from complete, it seems that the identity of consonants is at least in part encoded in the preceding vowel, but that in other types of sequences, the perceptual effect of coarticulation is negligible. In these studies investigating the perceptual correlates of anticipatory coarticulation, subjects have been presented with an utterance of at least a syllable. However, the final consonant can affect the structure of a syllable in more than one way. In particular, the effect can be predominantly spectral, as in the case of the nasalization of a vowel preceding a nasal consonant, or the effect can be predominantly temporal , as in the lengthening of vowels preceding voiced obstruents. The studies of the perceptual effects of anticipatory coarticulation certainly establish that coarticulation cues can be employed to identify deleted consonants ; however, the exact nature of the cues which subjects are using to make the identification is not specified.
314
Z. S. Bond
If vowel segments are excerpted from the vocalic portion of naturally occurring CVC syllables, the formant structure of the vowel segments and the consequ ent identification patterns will be different, depending on the following conso nant (Bond , 1976a, b). In other words, the coarticulation effects of at least some consonants affect the identification patterns of vowels when all but spectral cues of vowel and conso nant id entity are eliminated. An experiment was conducted to determine if these spectral cues are sufficient to enable subjects to predict the consonantal environment from which the vowel was excerpted . Method
Stimuli The four English vowels, /i, E, a , u j, which can be followed by the four consonants / n, I, d, r j were selected for study. Sixteen CVC syllables were constructed. The first consonant of the syllable was /h/, followed by each of the four vowels in combination with each of the four fin al consonants. Two male speakers of midwestern American English recorded the sequences under standard recording conditions. One pitch period was excerpted from each vowel. Using a PDP-1 computer, the analog signal of each word was digitized at 25 K samples/sand displayed on the CRT. One pitch period was selected and excerpted from approximately the mid-point of each vowel. The pitch period was stored for later recall and recording through a digital-to-analog converter. The tape which was used to test subjects was assembled from the excerpted pitch periods. For each stimulus item, 10 iterations of one pitch period were produced without pauses so that each test item was approximately 100 ms in duration . The listening tape consisted of three repetitions of four vowels from four phonetic contexts as produced by two speakers, for a total of 96 test item·s, presented in random order. The interstimulus interval was approximately 5 s. In several respects, stimuli created by this procedure are unnatural : the onset and offset of the vowel is abrupt ; the fundamental frequency is constant ; neither duration nor amplitude vary as in natural speech ; and any spectral changes are eliminated. On the other hand , the procedure serves to eliminate all but spectral cues for the context identification task, and thus makes it possible to assess the perceptual effects of spectral changes due to coarticulation quite directly. Furthermore, vowel tokens created by this procedure have been found to provide adequate spectral information for identification, yet also to be affected , in terms of identification patterns, by the following consonant (Bond, 1976a, b) .
Subjects Two groups of subjects were tested. The fi rst group, 12 undergraduate students at the University of Dayton, Dayton, Ohio, with no training in phonetics, were paid for their participation in the experiment. The second group, 14 undergraduate students enrolled in a phonetics course at Ohio University, Athens, Ohio, were given credit towards completion of course requirements for participation in the experiment. Testing procedure The testing procedure for both groups of subjects was identical. Subjects were instructed to listen to each test item very carefully, and to decide (or guess) if the vowel had been
Anticipatory coarticulation for English consonants
315
followed by /n/, /1/, /d/ or jrf. The listening tape was presented over earphones. Subjects recorded their decisions for each item on a prepared answer sheet. 100 .---------------------,-------------------, Context I II
Context l r I
u
'"
8 c
'"u
&!
Figure 1
The percent correct identification of the final consonant is given for each consonant (in the four quadrants) and vowel tested. The performance of the phonetically experienced subjects is represented by the dark bars; the performance of the phonetically untrained subjects is represented by the light bars.
Results and discussion
The per cent correct identification of each consonant, from the coarticulatory information contained in the vowel, is summarized in Fig. I, for both groups of subjects and for each vowel and consonant tested. It is apparent that for some combinations of vowels and final consonants, subjects were correct in identifying the consonant at better than chance expectation. However, for other vowel-consonant sequences, there was an equally strong tendency to respond with some other consonant than the correct. Overall performance was essentially at chance: 25% correct responses for the phonetically trained subjects and 26 % correct responses for the phonetically untrained subjects. Therefore, although for a few sequences of vowels and consonants, the subjects appeared to be able to guess the missing consonant, perhaps more emphasis should be placed on the over-all performance scores: given the methodology employed in this experiment it appears that the spectral information contained in one excerpted pitch period is not sufficient to enable subjects to identify the following consonant. The research reported in this paper was sponsored in part by the Neurophysiology Branch of the Aerospace Medical Research Laboratory, Aerospace Medical Division, Air Force Systems Command , Wright- Patterson Air Force Base, Ohio, 45433, and supported in part by a research associateship from National Research Council. The voluntary informed consent of the subjects used in this research was obtained as required by Air Force Regulation 80- 33. This paper has been identified by Aerospace Medical Research Laboratory as AMRL-TR-76-77.
References Ali, Latif, Gallagher, Tanya, Goldstein, Jeffrey, & Daniloff, Raymond (1971). Perception of coarticulated nasality. Journal of the Acoustical Society of America 49, 538-40. Bond, Z . S. (l976a) . Identification of vowels excerpted from neutral and nasal context. Journal of the Acoustical Society of America 59, 1229-32. Bond, z. S. (1976b). Identification of vowels excerpted from /1/ and /r/ contexts. Journal of the Acoustical Society of America 60, 906-10.
316
Z. S. Bond
Grimm, W. A. (1966). Perception of segments of English-spoken consonant-vowel syllables. Journal of the Acoustical Society of America 40, 1454-61. Kuehn, David P. & Moll, Kenneth L. (1972). Perceptual effects of forward coarticulation. Journal of Speech and Hearing Research 15, 654-64. Lehiste, lise and Shockey, Linda (1972). On the perception of coarticulation effects in English VCV syllables. Journal of Speech and Hearing Research 15, 500-506.