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Some observations on the nasal-fricative sequences in English
Journal of Phonetics (1982) 10, 315-323
Some observations on the nasal-fricative sequences in English Latif H. Ali University of Bagh dad, Baghdad, Iraq Received 27th October 1981
Abstract:
Based on the results obtained by Ali et al. ( 1979), an aerodynamic and spec trographic investigation of the nasal-fricative sequences in British English was made to examine the following possibilities. ( 1) The likelihood of the existence of the silence gaps in the above sequences. (2) The existence of certain consonants specified as [+nasal) other than the traditional nasal consonants, namely [ m), [ n) and [ l) ). The results confirm positively the first possibility with some divergence: but as for the second one, it is found that sounds like [ Tl)) (known as 'labio-dental nasal-fricative) are not nasal, but nasalized .
Introduction
The acoustic characteristics of the English consonants form a notable part of laboratory phoneticians literature (Ali et al., 1979; Fischer-J¢rgensen, 1975; Heffner, 1949; Klatt, 1967, 1973, 1975 ; Lewis eta!., 1975; Liberman eta!., 1958; Lisker, 1970, 1975; Lisker & Abramson, 1964; Malmberg, 1963; Mermelstein, 1977; Nestell, 1969); while less attention was paid to the sequences of consonant clusters. In their investigation, Lewis et al. (1975) observed large silent gaps between [n] and [e] sequences. Previous research work (Liberman et al., 1958) has demonstrated that a silent gap can cue the perception of a stop consonant within the cluster. It is a well known phenomenon that in a nasal-fricative (NF) clusters an oral gap may intrude between the nasal and the following fricative consonant sound (Ali et al., 1979). Harms (1973, p. 6) hypothesizes that "a nasal plus fricative sequence as the output of the phonological rules will automatically lead to an inserted stop at the level of sound production owing to the disparity in timing between the neural commands and the motor events". He goes further explaining that such a stop is homorganic with the nasal consonant only in respect to place of articulation; thus the word "warmth /w~rmO/ may be perceived as /w~ rmpO/. Some recent studies (Mermelstein, 1977) assert that it is important to treat the transition between nasal and non-nasal as a dynamic articulatory event with some acoustic properties. According to the aerodynamic point of view Fischer-J¢rgensen (1975) states that nasal consonants are often classified as stop consonants in that if the oral air pressure has begun to rise before the release of the nasal consonant, the rapid release of the nasal constriction could cause a burst-transition, which is also an important cue for stop consonant perception. This paper is designed to assess the likelihood of the above possibilities by conducting aerodynamic and spectrographic studies to investigate whether such silent gaps exist in British English (Standard British) nasal-fricative clusters, since all the above assumptions deal 0095-4470/82/030315 + 09 $03 .00/0
© 1982 Academic Press Inc. (London) Ltd.
316
L. H. Ali
with American English. Also, the investigation examines the possibility of the existence of certain consonants specified as [+nasal] other than the three traditional nasal consonants transcribed as [m], [n], and [IJ]; this depends completely upon the results of the aerodynamic investigation. This possibility may occur only in the absence of the silent gaps mentioned above. Some phonological explanation will account for it. Procedures The study consisted of calibrated nasal and oral air flow with duplex base and the pharyngeal voicing prints of the utterances used in the experiments, as aerodynamic criteria. Also a spectrographic analysis of the same words (containing NF clusters) was used with the same time calibration (128 mm/s). Subjects were three young adult female British native speakers who were staff members at the Department of Phonetics, Leeds University. All subjects were with normal speech and hearing. Table I represents the set of nine words containing the intended NF, clusters. In all cases, the N was followed by a voiceless F, because we believe that the process of tracing the pharyngeal voicing prints of the Non the following consonant would yield more objectively accurate results than if this fricative consonant was a voiced one; the latter case would definitely result in overlapping. Table I Words spoken by three subjects. Each word contains at least one internal NF cluster. The list was recorded eight times for each subject
Cluster type
Words
[ns]
[nfl]
anthropology institute inspector anthem anthology influence consistency
[nf]
[mf]
influence
comfortable emphasis
The list was spoken in a normal conversational level of natural speech within the phrase carrier "Say . .. . ... . please". Each subject was fitted with a close fitting mask of B.O.C. Medical Division. Each mask was a partitioned surgical anaesthetic type with a form fitting visco-elastic bridge to separate oral from nasal air streams. The mask, with very sensitive microphones fitted inside it to detect the acoustic-speech signals, was connected to a mingograph 803 , Siemens-Elma type and a Revox A77 tape recorder at the same time, so that the speech signals in one hand and nasal and oral flow signals, and noise frication plus voicing prints in the other, were recorded simultaneously. Though the face-mask distorted the audio signal, the same recordings were subject to voice print spectrographic analysis. For this purpose a Sound Spectrograph, type VII Voice Identification Inc., 700 Series, was used. Criterion measures The measurements were designed to be obtained from the following points. (1) Duration offriction noise (Dfn). (2) Duration of silent interval (Dsil) if any. (3) Duration of nasal air flow after end of nasal voicing (DNf). DNf to get the percentage. (4) Calculation of Dfn + Dsil ( 5) Height of nasal air flow .
Nasal-fricative sequences
317
The points of interest to be measured were accomplished according to the following .
(1) A line was drawn at the end of the laryngeal voicing. (2) A line was drawn at the start point of the duplex friction. (3) A line was drawn at the end point of the nasal air flow (see Fig. 1) .
-++1/8 " ' 24 ms
Duplex Ph. voicing
I I
s
Figure 1
ei?aen
e am
p
.(.
i:
s
A schematized aerodynamic-spectrographic tracing of the sentence "Say
anthem please." (subject 3). DNf = duration of nasal flow, DfN =duration of fricative noise, Dsil = duration of silent gap, NfL = nasal flow line, OfL = oral flow-line. Table II gap Cluster type [ns ]
The list of words perceived by three listeners as containing no silent Word
No silent gap , Silent gap only no burst
institute inspector influence consistency consistency
3 2 1
anthropology anthem anthology
1 1 2
[nf]
influence
2
[mf]
comfortable emphasis
[ne J
1
2 1 13
1 1 1 1
Burst and silent gap
1 2 1
2 2
Total 3 3 3 3 3 3 3 3
3
8
1 2 12
3 3 33
318
L. H Ali
The speech sample used consisted of nine words shown in Table I. All words contain NF clusters; each word contains one NF cluster except two wrods which contain two clusters each. The stress of each word was determined prior to the recording process. Each subj ec read the list (within the phrase carrier mentioned above) eight times during recording procedure. Then, a list of the nine words was randomly selected for each subject from the eigh t readings. Results
Inspection of the time aligned, the nasal air flow , the duplex base friction , and the laryngeal voicing prints, revealed that in 19 of the 33 cases for the NF clusters the friction noise of [nf] [mf] and [ne] began simultaneously with no more than 6ms after the point of peak nasal flow. In the other 14 cases the friction duration during which nasal flow was observed ranged from 14-52% of the duration of the friction noise. The case of [ns] appeared to behave a little differently. In all cases the first occurance of [ns] behaved in a similar way as shown above , except for "influence" where surprisingly it showed a similar behaviour to that of the second occurance of this sequence in "consistency"; except for subject two , both occurances have similarities in common. They are in unstressed syllables and both come as second occurances of NF in their environment. In all cases of this type of [ns], the friction noise started at the end of the second third of the nasal flow whose peak reached almost one third of the peak height of the other nasal flow of [ns] (8 mm height for the former and 26 mm average for the latter). The silent interval was sporadically observed; two subjects showed a silent gap in (mf] which ranges between 18-24 ms. One subject showed a gap between (mf] of "comfortable" and none for "emphasis" , while subject three showed a silent interval in two occurances, "comfortable" and "emphasis"; there was no gap observed for the third subject. The observed gap in this sequence comprises 26% of all six occurances of this sequence for the three subjects. The duration of the silent interval was about 35% of the [f) duration noise friction (21 and 72ms average respectively). The [ns] sequence showed an interesting behaviour. The first occurance of this cluster in "inspector", "institute" and "consistency" showed no silent gap ; while in the second NF in "consistency" and "influence" there was a gap , except for subject two. The observed gap in [ns] of "influence" was small in duration if compared to that of "consistency" (14 and 36 ms respectively). Thus, it would appear that for the sibilant fricatives, where a gap was observed in [ns]. the oral port opened promptly, well in advance of velopharyngeal closure, with devoicing being complete at about the point of greatest nasal air flow in most cases. For dental fricatives accompanied by a silent interval, it would appear that the larynx devoiced promptly, the velopharyngeal port remained open throughout the silent gap and sometimes into the friction noise , and the release of the oral stoppage into the fricative slit may well have been delayed. In 26 of the 33 cases, nesal air flow reached at peak or beyond the point where voicing of nasal vibrations had damped out (12 ms beyond the peak) . It is interesting to note that the peak ranged 24-33 mm height in all cases except that the (ns] of "influence" and its second occurance in "consistency" showed relatively a very low air flow (8 mm height average) . The nasal air flow, in all 33 tokens , continued through a substantial portion of the friction noise, where sometimes it covers the whole friction noise (see Fig. 2). The N flow for (mf] and (nf] appeared to have the same height (see Figs 3 and 4). The main difference one might observe here is that the [m] duration is slightly less than the [n] in the [-f) environment (see Table III).
Nasal-fricative sequences
k
Figure 2
a
n
s
319
s
t
a
n
s
A schematized aerodynamic-spectrographic tracing of the word "consistency" (subject 2).
Table III Average duration of three points of measurements for the four types of clusters for the three subjects
Cluster type [nsL [ns],
[n8] [nf] [mf]
Duration of friction noise
Duration of nasal flow
Duration of silent gap
103 106 66 80 75
212.5 176 273 225 187
31 42 13
ns 1 = first occurance of ns in a word. ns 2 = second occurance of ns or ns as a second occurance of NF in a word.
Wideband voice print spectrograms with overlaid average amplitude curves comprised the data for analysis . For the [mf] six sequences, only two subjects showed a silent gap in one sequence: that is in "comfortable " (see Fig. 4). No silent gap was observed in [nf] sequences (see Fig. 3). In all 15 cases of the [ns] clusters, there was no silent gap in the first syllable occurances. The [ne] sequences showed a gap in three cases only (3/9 cases) in "anthem" (42ms average). In all cases of the [ns] clusters, the amplitude of the [s] friction noise rose either steadily throughout the duration of the friction or it levelled off and/or declined. To demonstrate certain aerodynamic phenomena discussed above, Figs 1-4 contain
320
L. H Ali
n
Figure 3
.e
u a
n
5
A schematized aerodynamic-spectrographic tracing of the word "influence" (subject 1) .
schematized aerodynamic spectrographic traces of selected utternaces for the three subjects. In Fig. 1, notice that the intrusive stop in [a:n tUJm] is exemplified by both a silent gap and a transient burst release into the [8] ; also the peak nasal flow occurs during the silent gap and that in the other two subjects nearly two thirds of the fricative consonant are marked by nasal flow. The two types of [ns] are represented in Figs 2 and 3. Notice in Fig. 2 there is no gap in both occurances . Contrary to the first and third subjects whose aerodynamic and spectrographic traces show a gap in the second occurance of [ns] in the same word; that is "consistency". This figure shows not only the lack of a silent gap but also shows clearly that peak nasal flow is simultaneous with the onset of [s] friction whose 75% duration exhibits nasal flow . · Two types of NF clusters are represented in Fig. 3 which shows the aerodynamic and spectrographic rep resentations of the word "influence". Note that there is no silent gap between [n] and [f], while the gap is clearly shown between [n] and [s]. Notice the difference between the heights of peak nasal flow in both cases , where [ns] receives less than 25% of the nasal flow height observed in the [nf], or even in [ns] of the occurance in "consistency". Figure 4 presents the data in question for the word "comfortable". Observe that the peak nasal flow proceeds after the cessation of the nasal vibration print. Though the gap between [n] and [f] is small relatively , the burst for the intrusive homorganic [p] is clearly shown. Table III summarizes the results of the selected points of measures made on 33 tokens of the words listed in Table I. The obvious thing here is the close agreement among all figure s of the points of measures of the DNf, except for the [nO] cluster which is longer than the
Nasal-fricative sequences
k
Figure 4
A
m
f
321
t e
b
A schematized aerodynamic-spectrographic tracing of the word " comfortable" (subject 1). Table IV Aerodynamic and temporal measures made on the nine words (17 clusters) listed in Table I. Each mean percentage represents an average mean of the three production by the three subjects over number examplars of each NF type
Cluster type
Number of cases
Mean percentage of friction noise (plus silent gap)
Mean delay between the end of the nasal segment and the point of peak nasal flow
[ns] [n8] [nf] [mf]
15 9 3 6
30 .5 31.4 75.1 68.7
8.5 10.2 12.1 9.3
51.45%
10.025 ms
Average
others while the Dfn varies in duration. What is very obvious is the lack of the D sil in [nf] and [ns] sequences. Table IV shows a kind of agreement between the measurements for the apical and dental fricatives . Peak friction noise air flows seem relatively close in value . Also notice that the delay between the end of the nasal segment and the point of peak nasal flow is similar for both groups of sounds; that is apical and dental. Table V shows the average differences between peak nasal flow and the start point of duplex friction where it is obvious that the [n8] and [mf] represent a longer duration than the other two cases (23.7-24ms) .
322
L. H Ali Table V Average differences between peak nasal flow and start point of duplex friction in ms
[nf]
[mf]
[ns]
[n ]
12
24
16
23.7
Inspecting Table II, reveals the possibility that listeners might expect pauses at the juncture boundary and so were disposed to interpret such a gap as a stop consonant. Examining the results reveals that a majority of the words show no silent gap; only seven of 33 cases (or 16%) show silent gaps. Most surprisingly the [ns] clusters in unstressed syllables manifested silent gaps; four of 15 cases (26.6%). The nine cases of [n8] show only two cases with a silent gap, or 22% of all [nO] clusters exhibits a silent gap. Discussion The results of this study demonstrate certain facts about the articulatory dynamics of nasalfricative clusters in British English. These results show that for the types of nasal-fricative clusters discussed in this investigation, the nasal airflow achieves maximum flow either at or shortly after the offset of nasal vibration. And that nasal airflow covers almost the whole onset of the following fricative and sometimes moves over a small part of its offset, 14-65% of the friction noise manifests nasal airflow. This can be explained in terms of LR (leftright) velar coarticulation. A small silent gap has been shown in a few cases; in certain occurances of [mf] 16% of all occurances of [mf] and [ns] whenever it is a second occurance of NF (26.6% of all cases of [ns]). Also this gap was observed in 22% of all [n8] clusters. In all cases of NF clusters, nasal voicing comes gradually to an end before the nasal air flow reaches its peak; and no voicing prints were observed affecting the frication noise. These results lead to the conclusion that it may not be the timing of the devoicing gesture, nor the timing and extent of the LR velar coarticulation contribute heavily to the realization, perceptually speaking, of the intrusive steps, which can be explained in terms of the aerodynamic mechanism as that the delayed release of the oral occlusion for the nasal which delays , in turn , the oral friction onset. The LR coarticulation of velopharyngeal opening may shunt the oral air pressure, delaying air pressure build up, has been observed by Ali et al. (1979). The nasal occlusive is released tremendously , resulting in a burst transient prior to the onset of friction noise which rises in intensity as the velum continues to close and pulmonic air enters the oro-pharynx through the open devoiced vocal folds. Since nasal flow covers the onset of the fricative consonants in the above clusters, and no voicing effect could be traced on the fricatives , then one could conclude that these fricative sounds are nasalized ones; thus, the nasal fricative [rTJ] recognised by many phoneticians Heffner, 1949; Malmberg, 1963, is not a nasal but nasalized consonant. At this point, one may argue phonologically about the possible occurance of the intrusive homorganic stops in NF clusters. First, this intrusive stop is by no means a universal phenomenon; nor is it found in all dialects of English. Our data showed that even all speakers of a dialect do not exhibit such a phen.::Jmenon, which comes, as a result, in support of Zwicky's assumption (1972) and in agreement with Roca (1976). Therefore, a stop of this kind is not really a physiological necessity and thus, should not be represented in the lexical underlying representation. Accordingly, a word like "prince" can be perceived as [prints ], and the [t], here, should be introduced by a minor rule later, on one level or another , and should not be confused with the [t] of "prints" [prints] which is normally represented in the underlying representation of its lexical form.
Nasal-fricative sequences
323
To conclude, the problem appears to be one of those which account for how and why such sound changes take place. The results of this study confirm that coarticulation involving LR velar coarticualtion , and the timing and release characteristics of the nasal consonant should be regarded as one of the crucial articulatory dynamic factors involved in this change. References Ali, L. H., Daniloff, R. G. & Hammarberg, R. (1979) . Intrusive stops in nasai-fricative clusters: an aerodynamic and acoustic investigation. Phonetica, 36, 85-97. Fischer-J¢rgensen, E. (1975). Trends in Phonological Theory. Copenhagen: Akademisk Forlag. Fujmura, 0 . (1962) . Analysis of nasal consonants. Journal of the Acoustical Society of America, 34, 1865-1875. Harris, K. S., Lysaught , G. F. & Schvey , M. V. (1965). Some aspects of the production of oral and nasal labial stops. Language and Speech , 9, 135-14 7. Heffner, R. M.S. (1949). General Phonetics. Madison. Klatt, D. H. (1967). Articulatory activity and air flow during the production of fricative consonants. Massachusetts Institute of Technology, Quarterly Progress Report, 48, 257-260. Klatt, D. H. (1973). Durational characteristics of prestressed word initial consonant clusters. Massachusetts Institute of Technology, Quarterly Progress Report, 108, 253-260. Klatt, D. H. (1975). Voice onset time, frication and aspiration in word initial consonant clusters. Journal of Speech and Hearing Research, 18, 686-706. Lewis, J ., Daniloff, R. G. & Hammer berg, R. (1975). Apical co articulation and junctura! boundaries. Journal of Phonetics, 3, 1-7. Liberman, A.M ., DeLattre, P. C. & Cooper, F. S. (1958). Some cues for the distinction between voiced and voiceless stops in initial positions. Language and Speech , 1, 153-167. Liberman, A.M., Harris, K. S., Eimas, P. , Lisker, L. & Bastian, J. (1961). An effect of learning on speech perception: the discrimination of duration of silence with and without phonetic significance. Language and Speech, 4, 175-195. Lisker, L. (1970). Supraglottal air pressure in the production of English stops. Language and Speech, 13, 215-230. Lisker, L. (1975). Is it VOT or a first-formant transition detector? Journal of the Acoustical Society of America, 57, 154 7-1551. Lisker, L. & Abramson, P. C. (1964) . Across-language study of voicing in initial stops: acoustical measurements. Words, 20 , 384-422. Malmberg, R. (1963). Phonetics. New York: Dover Publications, Inc. Mermelstein, P. (1977). On detecting nasals in continuous speech. Journal of the Acoustical Society of America, 2, 581-587 . Nestell, R. (1969). Subglottal and intra-{)ral air pressure during the intervocalic contacts of /t/ and /d/. Phonetica, 20, 68-73 . Roca, I. M. (1976). Who is afraid of universal statements? Journal of Phonetics, 4 , 83-90. Stevens, K. N. (1971). Air flo w and turbulence noise for fricative and stop consonants. Journal of the Acoustical Society of America, 50, 1180-1192. Stevens, K. N. & Klatt, D. H. (1971). The role of formant transition in voice-voiceless distinction for stops. Journal of the Acoustical Society of America, 55, 653-659. Umeda, N. ( 1977). Consonant duration in American English. Journal of the Acoustical Society of America, 3, 846-858 . Zwicky, A.M. (1972). Note on a phonological hierarchy in English. In Linguistic Change and Generative Theory (Stickwall and McCawley Eds). Bloomington: Indiana University Press.
Some observations on the nasal-fricative sequences in English Latif H. Ali University of Bagh dad, Baghdad, Iraq Received 27th October 1981
Abstract:
Based on the results obtained by Ali et al. ( 1979), an aerodynamic and spec trographic investigation of the nasal-fricative sequences in British English was made to examine the following possibilities. ( 1) The likelihood of the existence of the silence gaps in the above sequences. (2) The existence of certain consonants specified as [+nasal) other than the traditional nasal consonants, namely [ m), [ n) and [ l) ). The results confirm positively the first possibility with some divergence: but as for the second one, it is found that sounds like [ Tl)) (known as 'labio-dental nasal-fricative) are not nasal, but nasalized .
Introduction
The acoustic characteristics of the English consonants form a notable part of laboratory phoneticians literature (Ali et al., 1979; Fischer-J¢rgensen, 1975; Heffner, 1949; Klatt, 1967, 1973, 1975 ; Lewis eta!., 1975; Liberman eta!., 1958; Lisker, 1970, 1975; Lisker & Abramson, 1964; Malmberg, 1963; Mermelstein, 1977; Nestell, 1969); while less attention was paid to the sequences of consonant clusters. In their investigation, Lewis et al. (1975) observed large silent gaps between [n] and [e] sequences. Previous research work (Liberman et al., 1958) has demonstrated that a silent gap can cue the perception of a stop consonant within the cluster. It is a well known phenomenon that in a nasal-fricative (NF) clusters an oral gap may intrude between the nasal and the following fricative consonant sound (Ali et al., 1979). Harms (1973, p. 6) hypothesizes that "a nasal plus fricative sequence as the output of the phonological rules will automatically lead to an inserted stop at the level of sound production owing to the disparity in timing between the neural commands and the motor events". He goes further explaining that such a stop is homorganic with the nasal consonant only in respect to place of articulation; thus the word "warmth /w~rmO/ may be perceived as /w~ rmpO/. Some recent studies (Mermelstein, 1977) assert that it is important to treat the transition between nasal and non-nasal as a dynamic articulatory event with some acoustic properties. According to the aerodynamic point of view Fischer-J¢rgensen (1975) states that nasal consonants are often classified as stop consonants in that if the oral air pressure has begun to rise before the release of the nasal consonant, the rapid release of the nasal constriction could cause a burst-transition, which is also an important cue for stop consonant perception. This paper is designed to assess the likelihood of the above possibilities by conducting aerodynamic and spectrographic studies to investigate whether such silent gaps exist in British English (Standard British) nasal-fricative clusters, since all the above assumptions deal 0095-4470/82/030315 + 09 $03 .00/0
© 1982 Academic Press Inc. (London) Ltd.
316
L. H. Ali
with American English. Also, the investigation examines the possibility of the existence of certain consonants specified as [+nasal] other than the three traditional nasal consonants transcribed as [m], [n], and [IJ]; this depends completely upon the results of the aerodynamic investigation. This possibility may occur only in the absence of the silent gaps mentioned above. Some phonological explanation will account for it. Procedures The study consisted of calibrated nasal and oral air flow with duplex base and the pharyngeal voicing prints of the utterances used in the experiments, as aerodynamic criteria. Also a spectrographic analysis of the same words (containing NF clusters) was used with the same time calibration (128 mm/s). Subjects were three young adult female British native speakers who were staff members at the Department of Phonetics, Leeds University. All subjects were with normal speech and hearing. Table I represents the set of nine words containing the intended NF, clusters. In all cases, the N was followed by a voiceless F, because we believe that the process of tracing the pharyngeal voicing prints of the Non the following consonant would yield more objectively accurate results than if this fricative consonant was a voiced one; the latter case would definitely result in overlapping. Table I Words spoken by three subjects. Each word contains at least one internal NF cluster. The list was recorded eight times for each subject
Cluster type
Words
[ns]
[nfl]
anthropology institute inspector anthem anthology influence consistency
[nf]
[mf]
influence
comfortable emphasis
The list was spoken in a normal conversational level of natural speech within the phrase carrier "Say . .. . ... . please". Each subject was fitted with a close fitting mask of B.O.C. Medical Division. Each mask was a partitioned surgical anaesthetic type with a form fitting visco-elastic bridge to separate oral from nasal air streams. The mask, with very sensitive microphones fitted inside it to detect the acoustic-speech signals, was connected to a mingograph 803 , Siemens-Elma type and a Revox A77 tape recorder at the same time, so that the speech signals in one hand and nasal and oral flow signals, and noise frication plus voicing prints in the other, were recorded simultaneously. Though the face-mask distorted the audio signal, the same recordings were subject to voice print spectrographic analysis. For this purpose a Sound Spectrograph, type VII Voice Identification Inc., 700 Series, was used. Criterion measures The measurements were designed to be obtained from the following points. (1) Duration offriction noise (Dfn). (2) Duration of silent interval (Dsil) if any. (3) Duration of nasal air flow after end of nasal voicing (DNf). DNf to get the percentage. (4) Calculation of Dfn + Dsil ( 5) Height of nasal air flow .
Nasal-fricative sequences
317
The points of interest to be measured were accomplished according to the following .
(1) A line was drawn at the end of the laryngeal voicing. (2) A line was drawn at the start point of the duplex friction. (3) A line was drawn at the end point of the nasal air flow (see Fig. 1) .
-++1/8 " ' 24 ms
Duplex Ph. voicing
I I
s
Figure 1
ei?aen
e am
p
.(.
i:
s
A schematized aerodynamic-spectrographic tracing of the sentence "Say
anthem please." (subject 3). DNf = duration of nasal flow, DfN =duration of fricative noise, Dsil = duration of silent gap, NfL = nasal flow line, OfL = oral flow-line. Table II gap Cluster type [ns ]
The list of words perceived by three listeners as containing no silent Word
No silent gap , Silent gap only no burst
institute inspector influence consistency consistency
3 2 1
anthropology anthem anthology
1 1 2
[nf]
influence
2
[mf]
comfortable emphasis
[ne J
1
2 1 13
1 1 1 1
Burst and silent gap
1 2 1
2 2
Total 3 3 3 3 3 3 3 3
3
8
1 2 12
3 3 33
318
L. H Ali
The speech sample used consisted of nine words shown in Table I. All words contain NF clusters; each word contains one NF cluster except two wrods which contain two clusters each. The stress of each word was determined prior to the recording process. Each subj ec read the list (within the phrase carrier mentioned above) eight times during recording procedure. Then, a list of the nine words was randomly selected for each subject from the eigh t readings. Results
Inspection of the time aligned, the nasal air flow , the duplex base friction , and the laryngeal voicing prints, revealed that in 19 of the 33 cases for the NF clusters the friction noise of [nf] [mf] and [ne] began simultaneously with no more than 6ms after the point of peak nasal flow. In the other 14 cases the friction duration during which nasal flow was observed ranged from 14-52% of the duration of the friction noise. The case of [ns] appeared to behave a little differently. In all cases the first occurance of [ns] behaved in a similar way as shown above , except for "influence" where surprisingly it showed a similar behaviour to that of the second occurance of this sequence in "consistency"; except for subject two , both occurances have similarities in common. They are in unstressed syllables and both come as second occurances of NF in their environment. In all cases of this type of [ns], the friction noise started at the end of the second third of the nasal flow whose peak reached almost one third of the peak height of the other nasal flow of [ns] (8 mm height for the former and 26 mm average for the latter). The silent interval was sporadically observed; two subjects showed a silent gap in (mf] which ranges between 18-24 ms. One subject showed a gap between (mf] of "comfortable" and none for "emphasis" , while subject three showed a silent interval in two occurances, "comfortable" and "emphasis"; there was no gap observed for the third subject. The observed gap in this sequence comprises 26% of all six occurances of this sequence for the three subjects. The duration of the silent interval was about 35% of the [f) duration noise friction (21 and 72ms average respectively). The [ns] sequence showed an interesting behaviour. The first occurance of this cluster in "inspector", "institute" and "consistency" showed no silent gap ; while in the second NF in "consistency" and "influence" there was a gap , except for subject two. The observed gap in [ns] of "influence" was small in duration if compared to that of "consistency" (14 and 36 ms respectively). Thus, it would appear that for the sibilant fricatives, where a gap was observed in [ns]. the oral port opened promptly, well in advance of velopharyngeal closure, with devoicing being complete at about the point of greatest nasal air flow in most cases. For dental fricatives accompanied by a silent interval, it would appear that the larynx devoiced promptly, the velopharyngeal port remained open throughout the silent gap and sometimes into the friction noise , and the release of the oral stoppage into the fricative slit may well have been delayed. In 26 of the 33 cases, nesal air flow reached at peak or beyond the point where voicing of nasal vibrations had damped out (12 ms beyond the peak) . It is interesting to note that the peak ranged 24-33 mm height in all cases except that the (ns] of "influence" and its second occurance in "consistency" showed relatively a very low air flow (8 mm height average) . The nasal air flow, in all 33 tokens , continued through a substantial portion of the friction noise, where sometimes it covers the whole friction noise (see Fig. 2). The N flow for (mf] and (nf] appeared to have the same height (see Figs 3 and 4). The main difference one might observe here is that the [m] duration is slightly less than the [n] in the [-f) environment (see Table III).
Nasal-fricative sequences
k
Figure 2
a
n
s
319
s
t
a
n
s
A schematized aerodynamic-spectrographic tracing of the word "consistency" (subject 2).
Table III Average duration of three points of measurements for the four types of clusters for the three subjects
Cluster type [nsL [ns],
[n8] [nf] [mf]
Duration of friction noise
Duration of nasal flow
Duration of silent gap
103 106 66 80 75
212.5 176 273 225 187
31 42 13
ns 1 = first occurance of ns in a word. ns 2 = second occurance of ns or ns as a second occurance of NF in a word.
Wideband voice print spectrograms with overlaid average amplitude curves comprised the data for analysis . For the [mf] six sequences, only two subjects showed a silent gap in one sequence: that is in "comfortable " (see Fig. 4). No silent gap was observed in [nf] sequences (see Fig. 3). In all 15 cases of the [ns] clusters, there was no silent gap in the first syllable occurances. The [ne] sequences showed a gap in three cases only (3/9 cases) in "anthem" (42ms average). In all cases of the [ns] clusters, the amplitude of the [s] friction noise rose either steadily throughout the duration of the friction or it levelled off and/or declined. To demonstrate certain aerodynamic phenomena discussed above, Figs 1-4 contain
320
L. H Ali
n
Figure 3
.e
u a
n
5
A schematized aerodynamic-spectrographic tracing of the word "influence" (subject 1) .
schematized aerodynamic spectrographic traces of selected utternaces for the three subjects. In Fig. 1, notice that the intrusive stop in [a:n tUJm] is exemplified by both a silent gap and a transient burst release into the [8] ; also the peak nasal flow occurs during the silent gap and that in the other two subjects nearly two thirds of the fricative consonant are marked by nasal flow. The two types of [ns] are represented in Figs 2 and 3. Notice in Fig. 2 there is no gap in both occurances . Contrary to the first and third subjects whose aerodynamic and spectrographic traces show a gap in the second occurance of [ns] in the same word; that is "consistency". This figure shows not only the lack of a silent gap but also shows clearly that peak nasal flow is simultaneous with the onset of [s] friction whose 75% duration exhibits nasal flow . · Two types of NF clusters are represented in Fig. 3 which shows the aerodynamic and spectrographic rep resentations of the word "influence". Note that there is no silent gap between [n] and [f], while the gap is clearly shown between [n] and [s]. Notice the difference between the heights of peak nasal flow in both cases , where [ns] receives less than 25% of the nasal flow height observed in the [nf], or even in [ns] of the occurance in "consistency". Figure 4 presents the data in question for the word "comfortable". Observe that the peak nasal flow proceeds after the cessation of the nasal vibration print. Though the gap between [n] and [f] is small relatively , the burst for the intrusive homorganic [p] is clearly shown. Table III summarizes the results of the selected points of measures made on 33 tokens of the words listed in Table I. The obvious thing here is the close agreement among all figure s of the points of measures of the DNf, except for the [nO] cluster which is longer than the
Nasal-fricative sequences
k
Figure 4
A
m
f
321
t e
b
A schematized aerodynamic-spectrographic tracing of the word " comfortable" (subject 1). Table IV Aerodynamic and temporal measures made on the nine words (17 clusters) listed in Table I. Each mean percentage represents an average mean of the three production by the three subjects over number examplars of each NF type
Cluster type
Number of cases
Mean percentage of friction noise (plus silent gap)
Mean delay between the end of the nasal segment and the point of peak nasal flow
[ns] [n8] [nf] [mf]
15 9 3 6
30 .5 31.4 75.1 68.7
8.5 10.2 12.1 9.3
51.45%
10.025 ms
Average
others while the Dfn varies in duration. What is very obvious is the lack of the D sil in [nf] and [ns] sequences. Table IV shows a kind of agreement between the measurements for the apical and dental fricatives . Peak friction noise air flows seem relatively close in value . Also notice that the delay between the end of the nasal segment and the point of peak nasal flow is similar for both groups of sounds; that is apical and dental. Table V shows the average differences between peak nasal flow and the start point of duplex friction where it is obvious that the [n8] and [mf] represent a longer duration than the other two cases (23.7-24ms) .
322
L. H Ali Table V Average differences between peak nasal flow and start point of duplex friction in ms
[nf]
[mf]
[ns]
[n ]
12
24
16
23.7
Inspecting Table II, reveals the possibility that listeners might expect pauses at the juncture boundary and so were disposed to interpret such a gap as a stop consonant. Examining the results reveals that a majority of the words show no silent gap; only seven of 33 cases (or 16%) show silent gaps. Most surprisingly the [ns] clusters in unstressed syllables manifested silent gaps; four of 15 cases (26.6%). The nine cases of [n8] show only two cases with a silent gap, or 22% of all [nO] clusters exhibits a silent gap. Discussion The results of this study demonstrate certain facts about the articulatory dynamics of nasalfricative clusters in British English. These results show that for the types of nasal-fricative clusters discussed in this investigation, the nasal airflow achieves maximum flow either at or shortly after the offset of nasal vibration. And that nasal airflow covers almost the whole onset of the following fricative and sometimes moves over a small part of its offset, 14-65% of the friction noise manifests nasal airflow. This can be explained in terms of LR (leftright) velar coarticulation. A small silent gap has been shown in a few cases; in certain occurances of [mf] 16% of all occurances of [mf] and [ns] whenever it is a second occurance of NF (26.6% of all cases of [ns]). Also this gap was observed in 22% of all [n8] clusters. In all cases of NF clusters, nasal voicing comes gradually to an end before the nasal air flow reaches its peak; and no voicing prints were observed affecting the frication noise. These results lead to the conclusion that it may not be the timing of the devoicing gesture, nor the timing and extent of the LR velar coarticulation contribute heavily to the realization, perceptually speaking, of the intrusive steps, which can be explained in terms of the aerodynamic mechanism as that the delayed release of the oral occlusion for the nasal which delays , in turn , the oral friction onset. The LR coarticulation of velopharyngeal opening may shunt the oral air pressure, delaying air pressure build up, has been observed by Ali et al. (1979). The nasal occlusive is released tremendously , resulting in a burst transient prior to the onset of friction noise which rises in intensity as the velum continues to close and pulmonic air enters the oro-pharynx through the open devoiced vocal folds. Since nasal flow covers the onset of the fricative consonants in the above clusters, and no voicing effect could be traced on the fricatives , then one could conclude that these fricative sounds are nasalized ones; thus, the nasal fricative [rTJ] recognised by many phoneticians Heffner, 1949; Malmberg, 1963, is not a nasal but nasalized consonant. At this point, one may argue phonologically about the possible occurance of the intrusive homorganic stops in NF clusters. First, this intrusive stop is by no means a universal phenomenon; nor is it found in all dialects of English. Our data showed that even all speakers of a dialect do not exhibit such a phen.::Jmenon, which comes, as a result, in support of Zwicky's assumption (1972) and in agreement with Roca (1976). Therefore, a stop of this kind is not really a physiological necessity and thus, should not be represented in the lexical underlying representation. Accordingly, a word like "prince" can be perceived as [prints ], and the [t], here, should be introduced by a minor rule later, on one level or another , and should not be confused with the [t] of "prints" [prints] which is normally represented in the underlying representation of its lexical form.
Nasal-fricative sequences
323
To conclude, the problem appears to be one of those which account for how and why such sound changes take place. The results of this study confirm that coarticulation involving LR velar coarticualtion , and the timing and release characteristics of the nasal consonant should be regarded as one of the crucial articulatory dynamic factors involved in this change. References Ali, L. H., Daniloff, R. G. & Hammarberg, R. (1979) . Intrusive stops in nasai-fricative clusters: an aerodynamic and acoustic investigation. Phonetica, 36, 85-97. Fischer-J¢rgensen, E. (1975). Trends in Phonological Theory. Copenhagen: Akademisk Forlag. Fujmura, 0 . (1962) . Analysis of nasal consonants. Journal of the Acoustical Society of America, 34, 1865-1875. Harris, K. S., Lysaught , G. F. & Schvey , M. V. (1965). Some aspects of the production of oral and nasal labial stops. Language and Speech , 9, 135-14 7. Heffner, R. M.S. (1949). General Phonetics. Madison. Klatt, D. H. (1967). Articulatory activity and air flow during the production of fricative consonants. Massachusetts Institute of Technology, Quarterly Progress Report, 48, 257-260. Klatt, D. H. (1973). Durational characteristics of prestressed word initial consonant clusters. Massachusetts Institute of Technology, Quarterly Progress Report, 108, 253-260. Klatt, D. H. (1975). Voice onset time, frication and aspiration in word initial consonant clusters. Journal of Speech and Hearing Research, 18, 686-706. Lewis, J ., Daniloff, R. G. & Hammer berg, R. (1975). Apical co articulation and junctura! boundaries. Journal of Phonetics, 3, 1-7. Liberman, A.M ., DeLattre, P. C. & Cooper, F. S. (1958). Some cues for the distinction between voiced and voiceless stops in initial positions. Language and Speech , 1, 153-167. Liberman, A.M., Harris, K. S., Eimas, P. , Lisker, L. & Bastian, J. (1961). An effect of learning on speech perception: the discrimination of duration of silence with and without phonetic significance. Language and Speech, 4, 175-195. Lisker, L. (1970). Supraglottal air pressure in the production of English stops. Language and Speech, 13, 215-230. Lisker, L. (1975). Is it VOT or a first-formant transition detector? Journal of the Acoustical Society of America, 57, 154 7-1551. Lisker, L. & Abramson, P. C. (1964) . Across-language study of voicing in initial stops: acoustical measurements. Words, 20 , 384-422. Malmberg, R. (1963). Phonetics. New York: Dover Publications, Inc. Mermelstein, P. (1977). On detecting nasals in continuous speech. Journal of the Acoustical Society of America, 2, 581-587 . Nestell, R. (1969). Subglottal and intra-{)ral air pressure during the intervocalic contacts of /t/ and /d/. Phonetica, 20, 68-73 . Roca, I. M. (1976). Who is afraid of universal statements? Journal of Phonetics, 4 , 83-90. Stevens, K. N. (1971). Air flo w and turbulence noise for fricative and stop consonants. Journal of the Acoustical Society of America, 50, 1180-1192. Stevens, K. N. & Klatt, D. H. (1971). The role of formant transition in voice-voiceless distinction for stops. Journal of the Acoustical Society of America, 55, 653-659. Umeda, N. ( 1977). Consonant duration in American English. Journal of the Acoustical Society of America, 3, 846-858 . Zwicky, A.M. (1972). Note on a phonological hierarchy in English. In Linguistic Change and Generative Theory (Stickwall and McCawley Eds). Bloomington: Indiana University Press.