Kolia phoniat. 27: 423 437 (1975)
Simultaneous Oral and Nasal Airflow during Stop Consonant Production by Hearing-Impaired Speakers H.R. Gilbert Speech Science Laboratory, The Pennsylvania State University, University Park. Pa.
Introduction Characteristics which have been described as typical of hearing-impaired speech include slow rate (Voelker, 1935, 1938; Colton and Cooker, 1968), high pitch (Haycock, 1942; Ewing and Ewing, 1946; Boone, 1966), breathiness (Peterson, 1946; Silverman, 1960), misarticulations (Hudgins, 1934; Hudgins and Numbers, 1942; Silverman, 1960; Calvert, 1963\ D¡Carlo, 1964; Schwab, 1964), nasality (Voorhees, 1940; Haycock, 1942; Hudgins and Numbers, 1942; Numbers, 1946; Peterson, 1946; Miller, 1960; Silverman, 1960), faulty rhythm and faulty intonation patterns (Hudgins and Numbers. 1942; Silverman, 1960; Schwab, 1964). Despite the recognized need for research concerned with the speech of hearing-impaired individuals, only a few researchers (Bensen, 1951; McClumpha, 1966; Smith and Hutchinson, 1974) have used objective measures to study the physiological characteristics of hearing-impaired speech. Two studies have employed airflow-sensing systems, Bensen (1951) who used nasal u-tubes and Smith and Hutchinson (1974) who employed total airflow measure ments. To date, no one has used simultaneous oral and nasal airflows to study the aerodynamics of hearing-impaired speech. It would appear that a system using flow-sensing instrumentation designed to obtain simultaneous oral and nasal airflow measurements during stop conso nant production by hearing-impaired individuals can provide (1) objective data in the form of aerodynamic characteristics of hearing-impaired speech, and (2) a comparison of airflow data obtained from hearing-impaired speakers with avail able data from normally hearing subjects. Accordingly, the present investigation
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Received: September 1, 1975; accepted: September 15, 1975.
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was designed to fulfill the above needs through a study of the effects of ( 1) place of articulation (2) voicing, and (3) phonetic context upon simultaneous oral and nasal airflows during production of stop consonants by hearing-impaired speak ers.
Method Instrumentation A large anesthesia mask was modified in order to provide a means for independent channeling of oral and nasal airflows. The mask was divided into oral and nasal chambers by a hard rubber diaphragm which fitted snugly against the upper lip. The regular outlet of the mask served as an opening through which oral airflow was directed to one pneumotachome ter while nasal airflow was channeled to a second pneumotachometer through an outlet drilled into the front wall of the nasal chamber. figure 1 is a block diagram of the instrumentation used in the present study. The general technique used to record volume rate of oral and nasal airflows was similar to the pneumotachographic procedure described by Lubker and Moll (1965). Both oral and nasal airflow rates were determined by systems consisting of (1) a Fleisch pneumotachometer. (2) a Statham model I’M-15 bidirectional differential airpressure transducer, (3) an Accudata model 113 bridge amplifier, (4) a Honeywell M16S0 galvanometer, and (5) a Honeywell model 1508A Visicordcr direct-recording optical oscillo graph. The airflow-sensing systems were calibrated against a rotometer. The system used to sense the speech signal consisted of ( l ) a Grason-Stadlcr model E7300M throat microphone. (2) an Accudata model 120 DC amplifier, (3)3 Honeywell model M1650 galvanometer, and (4) a Honeywell model 1508A Visicorder. The output of this system served as an index of the acoustic onset and cessation of consonants and vowels. Subjects Ten subjects, 5 males and 5 females, ranging in age from L6 to 26 years, participated in the present investigation. All subjects were diagnosed as having moderate to profound bilateral sensorineural hearing losses. The hearing loss in each case was determined to be congenital or onset during the first year of life as ascertained from medical histories. All the hearing-impaired subjects exhibited a minimum hearing loss of 65 dB in the frequencies 500,
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Fig. I. A diagram of the instrumentation used in the present study.
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1,000, and 2,000 Hz. The subjects had no other handicap other than the hearing impair ment. The speech of the 10 subjects was rated by 3 teachers of the hearing-impaired and was judged in each case to be typical of hearing-impaired speakers. A further criterion for inclusion in the present study was that each speaker fit into the modified face mask, so that the seals around the edges of the mask and between the oral and nasal chambers were airtight (Lubker and Moll, 1965). Speech Sample The speech sample consisted of isolated syllables constructed so that the sample con tained both voiced and voiceless stop consonants, various places of articulation, and various phonetic contexts in the exploded mode of production. The test phonemes in these syllables were the 6 English stop consonants /p, t, k, b, d, g/, each produced in the pre-, inter-, and postvocalic phonetic contexts in combination with the neutral vowel /A/, i.c. /pAp, ApA/. F.ach of the 12 syllables was produced 3 times in succession with a brief pause between productions / pAp, pAp, pAp/. No attempts were made to change the productions of the speakers. They were asked to produce the utterances to the best of their abilities.
Results
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Oral Airflow Profiles Figures 2 a, b present the characteristic features for the voiced stops and which, in many respects, represent the essential features for the voiceless stops. Figure 2a is an example of a recording of the syllable /dAd/. As may be seen in the oral airflow profile of figure 2 a, an inspiratory flow of small magnitude and short duration is noted prior to the marked rise in flow rate. The next activity is an extremely rapid volume acceleration associated with the prevocalic / d/. Upon reaching a peak value, the flow rate begins a rapid deceleration. As the decelera tion proceeds, it is characterized by rapid a.c. fluctuations in rate of flow which continue through the vowel. Upon cessation of the vowel, the flow rate de creases to zero. The first activity observed in the flow record for the postvocalic Id/ is a marked volume acceleration in a positive direction. Upon attainment of the maximum value, a.c. fluctuations are again noted. The acoustical record shows voicing from the prevocalic consonant through the vowel. Upon cessation of the vowel, voicing ends. Voicing is again noted in association with the post vocalic consonant. Figure 2 b shows a recording of the syllable / AgA/. Many of the features which typify the CVC utterances are also apparent in the VCV oral airflow profiles. As can be seen in figure 2 b, there is a lack of a.c. fluctuations through out the oral airflow trace with a similar lack of voicing continuity in the acous tical record. Voicing is associated with the initial vowel, followed by an interval where no activity in the acoustical record is noted. With the volume acceleration associated with the intervocalic consonant, voicing is again apparent and con tinues through the final vowel.
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For legend, see p. 428.
Nasal A irflow Profiles Seven subjects consistently exhibited nasal airflows during production of the speech samples studied. 1 subject exhibited only slight nasal airflows asso ciated with the Ipl and /b/ phonemes in the pre- and intervocalic phonetic contexts. 2 subjects showed nasal flows which occurred either during or after cessation of the final phoneme in the sequence. In addition, several different nasal airflow patterns were apparent. These different flow profiles were not mutually exclusive in that one subject may have, and often did, exhibit more than one type of pattern. Figure 2c is a profile of the syllable /pAp/ and illustrates the essential features of the first group of nasal airflow profiles. In this group, peak nasal flows coincide in time with peak oral flows associated with the pre- and post vocalic stops. This general pattern was observed consistently in 7 subjects for/p, t, k/ in the 3 phonetic contexts. For the voiced stop plosives, the number of
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Inspiratory Jluws. Inspiratory or negative flows in the oral flow profiles occurred for 9 of the 10 subjects. These flows were primarily associated with the /k/ and /g/ phonemes occurring somewhat less frequently with It. d, p, b/. These inspiratory flows occurred most often in the pre- and intervocalic phonetic contexts. Only in a few cases were inspiratory flows present in the postvocalic context. The negative flows ranged in value from 0.5 to 9.35 liters/min.
427
subjects exhibiting this pattern varied from 3 for the prevocalic / g/ to 7 subjects for the pre- and postvocalic /b/. As seen in figure 2c, peak oral airflows lead slightly in time peak nasal airflows. The degree to which oral and nasal airflows were out of phase varied with each subject. Figure 2d represents a record of the syllable /kAk/ and is illustrative of a second group of profiles. 4 subjects consistently showed nasal airflows which either coincided with production of the vowel or occurred in the interval be tween the vowel and the postvocalic consonant in the CVC syllable. The first nasal flow activity noted in figure 2d occurs just prior to the rapid volume acceleration in oral flow associated with the prevocalic / k/. Nasal flow activity is again seen during production of the initial consonant with the peak nasal flow occurring sometime after cessation of the vowel. Nasal flow of small magnitude is again observed during the deceleration phase of oral airflow for the postvocalic /k/. This pattern was also observed in VCV syllables associated with either vowel or in the interval between the initial vowel and consonant or between the con sonant and final vowel. The second pattern of nasal flows occurred with equal frequency for both the voiced and voiceless stops. Figures 2e, f are profiles of the syllables /pAp/ and /AtA/, respectively, and illustrate a third group of profiles. This pattern is represented by nasal airflows occurring in conjunction with both the consonant and vowel production in CVC and VCV syllables. The first notable nasal flow activity in the syllable /pAp/
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Aerodynamic Characteristics ot' Hearing-Impaired Speech
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begins sometime after the attainment of peak oral flow associated with the prevocalic /p/. Peak nasal How occurs at the end of the deceleration phase of the oral airflow associated with the initial consonant. The next nasal flow activity noted occurs towards the end of the vowel production with a final peak nasal flow occurring in conjunction with the postvocalic /p/. In the syllable /AtA/, the first nasal flow activity is associated with the initial vowel. Nasal flow is next noted in conjunction with the intervocalic / 1/. As seen in figure 2 f, peak oral flow associated with / 1/ leads slightly peak nasal flow. The next nasal flow
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Fig. 2. Oral and nasal flow rate profiles and speech signal for the syllables /dAd/ (a), /AgA/ (b), /pAp/ (c), /kA k/ (d), /pAp/ (e), /A tA / (0, and /kAk/ (g).
429
Aerodynamic Characteristics of Hearing-Impaired Speech
Table I. Mean peak oral flow rates (liters/min) and standard deviations presented in rank order of magnitude for the 6 stops in 3 phonetic contexts as produced by the 10 hearing-impaired speakers Prevocalic
Intervocalic
Postvocalic
con sonant
mean * SD
con sonant
mean ± SD
con sonant
mean i SD
in /p/ M /d / M M
91.05 86.22 79.18 57.48 47.24 42.88
N N 111 IM /g/ /b/
86.24 77.65 76.57 54.18 41.91 36.44
ipi /k/ III Idl Isl /w
69.13 67.91 59.72 47.80 41.70 41.09
± 27.17 i 33.87 ± 26.94 i 19.38 ± 16.04 i 19.37
t 28.52 ± 28.69 ± 38.51 t 23.05 i 16.08 t 23.90
± 34.70 t 30.38 ± 27.88 t 20.75 ± 16.22 t 23.28
activity is associated with the final vowel. The nasal flow accelerates slowly during the vowel with a peak flow occurring after cessation of the vowel. This general pattern of profiles occurred most frequently in the CVC paradigm with the voiceless stops. Figure 2 g which is a profile of the syllable / kAk/ shows the essential fea tures of a fourth pattern of nasal airflows exhibited by 2 subjects. Nasal airflows, in this pattern, occurred at utterance end. While nasal airflows may have started during the final phoneme in the sequence, peak (low rate did not occur until sometime after cessation of the final phoneme.
The 0.05 % level of confidence was used in all statistical tests reported in this study.
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Peak Oral Flow Rate Measurements Table I presents the means and standard deviations of the peak oral flow rates for the stops in the 3 phonetic contexts as produced by the speaker group. On the basis of peak oral flow rate, several differences among the stops are clearly evident. Regardless of phonetic context, mean peak oral flow rates were greater for the voiceless stops than for their voiced cognates. With the exception of the It, d/ comparison in the postvocalic phonetic context, each of the voice less stops was accompanied by signigicantly1 greater mean peak oral airflow rates than its voiced cognate. When comparing peak oral flow rates with regard to phonetic context, peak flow rates were greater in the pre- than in the postvocalic phonetic context. Significant differences were found only for /p, t, k/. Peak flow rates were greater in the pre- than in the intervocalic phonetic context. No differences, however,
430
Gilbert
Table II. Mean peak nasal flow rates (liters/min) presented in rank order of magnitude for the 6 stops in 3 phonetic contexts as produced by the 10 hearing-impaired speakers Prevocalic
Postvocalic
Intervocalic
con sonant
n
mean
con sonant
n
mean
con sonant
n
mean
N Ipl M W M l&l
7 8 6 4 7 3
6.34 5.60 5.54 3.12 2.07 1.60
m M Ipl Ibl l&l IV
6 7 8 6 4 5
7.49 5.27 5.18 2.38 2.18 2.01
ipi /k / N 1V l&l
7 6 7 5 4 7
5.97 5.77 5.41 5.75 5.43 3.02
Peak Nasal Flow Rate Measurements Table II presents the mean peak nasal flow rates as produced by the speaker group. No statistical tests were performed on the peak nasal airflow data because the number of subjects contributing to the mean was small and varied for the specific phoneme being produced. However, several patterns were evident from the data presented. With the exception of the /t, d/ comparison in the postvo calic phonetic context, mean peak nasal flow rates were greater for the voiceless stop consonants than for their voiced cognates. This trend was noted for all speakers with only a few exceptions. A comparison of peak nasal airflow rates with respect to phonetic context indicated that, with the exception of /t/, nasal flows were greater in the postvo calic context than in the pre- or intervocalic phonetic contexts. Greater nasal flows were associated with /p, k, d/ in the pre- than in the intervocalic context. While for / 1, b, g/, peak nasal airflows were greater in the inter- than in the prevocalic phonetic context.
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were found to be significant. When the data were compared between the interand postvocalic phonetic contexts, 5 of the 6 consonants exhibited higher mean flow rates in the intervocalic phonetic context. Significant differences were found only for the / 1/. With regard to place of articulation, consonant rank order for the voiceless stops appeared to depend upon phonetic context. Consonant rank order for the voiced stop consonants was invariant across phonetic context. Results of statis tical contrasts within the voiceless category indicated that /t/ had a significantly higher flow rate that /k/ in the prevocalic phonetic context. For the voiced consonants, / d/ was found to exhibit significantly higher flow rates than / b/ in both the pre- and intervocalic phonetic contexts.
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Examining table II with reference to place of articulation, consonant rank order for both the voiceless and voiced stops is dependent upon phonetic con text.
Oral Airflow Profiles Oral flow rate profiles obtained in the present study for the voiced and voiceless stops were similar to those described by Gilbert (1973) who character ized stop consonant production as a three-stage model. The three stages which occurred consecutively were: (1) a reduction in oral flow rate which is related to an increase in vocal tract constriction, (2) a cessation of oral flow associated with an infinite resistance to respiratory flow brought about by a complete closure of the vocal tract at some point, and (3) a marked increase in oral flow which is associated with a rapid opening of the vocal tract. A feature noted by Gilbert (1973) in conjunction with the voiced stops was rapid a.c. fluctuations in the oral flow rate throughout the model. The fluctuations were associated with continuous periods of voicing in the acoustical record and supported the obser vations of Fant (1962) relative to the continuity of vocal cord vibration over a series of voiced sounds. While production of stop consonants by the hearing-impaired speakers con formed to the three-stage model discussed by Gilbert (1973), one unique feature was noted. The feature which was associated with voiced stop production con sisted of a lack of both continuous a.c. fluctuations in the oral airflow record and continuous voicing in the acoustical record. In the CVC paradigm, voicing ended after cessation of the vowel and was not noted again until the onset of the postvocalic consonant. A.c. fluctuations in the flow profile typically were not seen during this interval. In the VCV syllables, voicing and a.c. fluctuations ended after cessation of the initial vowel. Acoustical activity was again noted with the onset of the intervocalic consonant and continued through the final vowel. The lack of continuity of voicing perhaps can be attributed to analytical methods frequently used in teaching speech to hearing-impaired individuals. These methods emphasize mastery of individual phonemes with a gradual com bination of phenemes into meaningful units. These techniques do not stress the timing effects of coarticulation and typically rob the individual’s speech of its naturalness. With regard to inspiratory flows, the present findings support the results reported by Gilbert (1973) that negative flows occurred most often with /k/ and /g/. He attributed these inspiratory flows to posterior movements of the articula tors which bring about volumetric changes in the cavity between the screen of the pneumotachometer and the articulatory structures. In the present study,
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Discussion
con sonant
N Ip/ N
/d / /g /
M
Postvocalic
Intervocalic hearingimpaired mean ±SD
mean
91.05 86.22 79.18 57.48 47.24 42.88
107.33 i 23.48 91.76 ± 24.07 92.05 i 23.79 58.40 t 14.86 38.98 ± 14.40 40.92 ± 14.91
27.17 ± 33.87 i 26.94 ± 19.38 i 16.04 ± 19.37 ±
normals ±
con sonant SD N N Ipl
/d/ iBl lb/
hearingimpaired mean ± SD
normals
86.24 t 28.52 77.65 + 28.69 76.57 < 38.51 54.18 * 23.05 41.91 ± 16.08 36.44 ± 23.90
85.74 t 28.14 74.42 ± 26.90 75.98 ± 27.85 44.31 i 13.45 31.38 -t 12.53 34.42 i 12.21
mean
±
con sonant SD ip i /k /
N /d /
/g/ Ibl
hearingimpaired mean ± SD
normals
69.13 i 34.70 67.91 ± 30.38 59.72 * 27.88 47.80 ± 20.75 41.70 ± 16.22 41.09 t 23.28
77.57 i 29.99 61.08 * 23.70 75.55 i 29.02 36.12 i 13.57 31.71 i 11.51 32.12 ± 13.94
mean
t
SD
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Prevocalic
Gilbert
Table III. A comparison of mean peak oral How rates (liters/min) and standard deviations for the 6 stops in 3 phonetic contexts as produced by the 10 hearing-impaired speakers with those values reported by Gilbert (1973) for 9 normally hearing speakers
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inspiratory flows did not occur as frequently nor were they as great in magni tude as those negative Hows obtained by Gilbert (1973) from a normally hearing population. A possible explanation for the difference in results may be due to the speaker group studied. From the nature of the negative flows obtained, it would appear that posterior movements of the articulators in the hearing-im paired speakers were more restricted than in the normally hearing population, resulting in fewer negative Hows and negative (lows of smaller magnitudes. It is clear, however, that the airflow records of the present study provided only indirect information about articulatory events. As a consequence, further infor mation concerning articulator motility in hearing-impaired speakers must await further study.
Peak Airflow Rates Table III compares the mean peak oral airflow rates and standard deviations for the hearing-impaired subjects in the present study and the values reported by
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Nasal A irflow Profiles Nasal airflows consistently occurred during the test syllables as produced by 7 of the 10 hearing-impaired subjects. 1 subject exhibited only slight nasal flows, while for 2 subjects nasal airflows occurred during the last phoneme in the syllable or at utterance end. When the nasal airflow profiles of the 10 subjects were examined, a number of different nasal airflow patterns were evident. These findings support the cinefluorographic observations of McClumpha (1966) who found considerable variation among deaf speakers in both extent and duration of velopharyngeal function. In the 5 deaf speakers studied by AlcClump ha, velo pharyngeal function ranged from no closure on the speech samples studied to function similar to that of normals. The nasal airflow profiles obtained in the present study support the hypothesis that hearing-impaired speakers represent a heterogeneous population with regard to velopharyngeal function. In several subjects, peak nasal flows associated with both stop consonant and vowel production did not coincide with peak oral flows. In both cases, it appeared that peak oral airflows lead in time the peak nasal airflows. It was also evident from the profiles that peak nasal flows occurred during the closure phase of stop consonant production where no oral flow was observed or occurred after cessation of a phoneme at utterance end. The nasal flow profiles obtained in the present study may reflect an inability of the hearing-impaired speaker to coor dinate velopharyngeal function with the activity of other speech articulators. Martony (1965), in an attempt to specify differences in the speech of normally hearing and deaf boys between the ages of 13 and 15, found abnormal and misplaced nasalization of vowels and too early denasalization of nasal conso nants. His findings clearly indicated that one of the characteristics of hearingimpaired speech was a lack of coordination among articulators.
434
1
■
1
- M wM^cn
aioo-
_ol o1 o1 o]__o1__o1_o_1_o_1_o_1_o_1_o1
Gilben
IU Ipt
/k/ /d/
Ptevocalic
11 Iql Ibl
l \ l /k7 /p/ /d/ /g/ /b/
Intervocalic
Postvocahc
Gilbert (1973) for normally hearing subjects. The mean values in table 111 are also graphically portrayed in figure 3. The peak oral airflows are remarkably similar for the two groups of subjects. In the prevocalic phonetic context, the normally hearing subjects exhibited greater peak Hows for /t. p, k. d/, while the hearing-impaired subjects showed somewhat higher Hows for /g, b/. The hearingimpaired subjects showed somewhat higher mean peak oral airflows for all the phonemes in the intervocalic phonetic context. Ir. the postvocalic phonetic con text, greater peak flows for /k. d, g, b/ were exhibited by the hearing-impaired speakers, while the normal speakers exhibited higher oral flows for /p, t/. The peak oral airflows obtained in the present study were greater than those values reported by Emanuel and Counihan (1970) for normal subjects. They used a divided face mask with two warm wire anemometers to assess simulta neous oral and nasal airflows. Those studies which have used warm-wire anemometry to assess airflow events (Subtelny el al., 1966; Emanuel and Counihan
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Fig. 3. A graphic representation of mean peak oral now rate values (liters/min) during production of the 6 stop consonants in 3 phonetic contexts as produced by the 9 normally hearing speakers (■) reported by Gilbert (1973) and 10 hearing-impaired speakers O') ob tained from the present study.
Aerodynamic Characteristics of Hearing-Impaired Speech
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1970) have consistently reported peak flow rates well below values reported in studies where face mask-pneumotachographic procedures were used. Subtelny et al. (1966) have attributed these differences to an increased effort required to overcome resistance imposed by the face mask. Emanuel and Counihan (1970) used a face mask and reported peak flow values for stop consonant production which were less than those reported by Gilbert (1973) for normal subjects. It appears that the difference in basic flow instrumentation rather than the use of a face mask may account for the differences in peak flows obtained by Emanuel and Counihan (1970) and those reported by Gilbert (1973) and flow values reported in the present study. Smith and Hutchison (1974) reported total airflow rates for stop consonant production by an adult hearing-impaired population that were lower in magni tude than the peak oral airflows obtained in the present investigation. Since airtight velopharyngeal closure may not occur during the speech of hearing-im paired individuals, the total flow measurements may not represent only oral articulatory events. With regard to peak nasal flow rates, Lubker and Moll (1965) observed from a normally hearing subject only slight nasal flows preceding or coincidental with the initiation of phonation during production of non-sense syllables. Emanuel and Counihan (1972) reported peak nasal flow rates for stop consonants be tween 0.12 to 1.54 liters/min for their normally hearing subjects. Warren (1967) reported that cleft-palate speakers with velopharyngeal inadequacy exhibited nasal flow rates greater than 10.5 liters/min. Peak nasal airflows obtained in the present investigation ranged from 0.57 to 21.45 liters/min. Mean peak nasal airflows (table II) for the hearing-impaired speakers were between those values reported for normals and nasal airflows reported for cleft-palate speakers with velopharyngeal inadequacy. The nasal flow patterns and peak nasal airflows obtained in the present study may not solely reflect velopharyngeal function. Research has shown that nasal airflows are also dependent upon size of oral port constriction {Lubker and Moll, 1965; Warren and Ryon, 1967), nasal resistance and respiratory effort (Warren and Devereux, 1966; Warren and Ryon, 1967). Furthermore, while the airflow-sensing system used in the present study has certain limitations (Lubker and Moll, 1965; and Gilbert, 1973) and by itself may not be sufficient to describe articulatory events, the simultaneous oral and nasal airflows provided appear to be of importance in specifying certain aerodynamic characteristics heretofore not studied in the speech of hearing-impaired individuals.
Simultaneous oral and nasal airflows were obtained from a group of moderately to profoundly hearing-impaired young adults during production of the stop consonants /p, t, k,
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Summary
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436
b, d, g/. Both oral and nasal airflow profiles as well as peak oral and nasal airflows are presented. Oral airflows were similar to those obtained from normally hearing subjects. Several different nasal airflow patterns were observed which suggest that the hearing-im paired population is heterogeneous with regard to velopharyngeal function.
Bensen, J.: An experimental study of the relationship between the amount of nasal emission of air and judged nasality; unpubl. MA thesis Morgantown West Virginia University (1951). Boone, D.R.: Modification of the voices of deaf children. Volta Rev. 68: 686 692 (1966). Calvert, D.R.: An approach to the study of deaf speech. Proc. 41st Conv. Am. Instr. Deaf, vol. 65, pp. 242 245 (1963). Colton, R.H. and Cooker, H.S.: Perceived nasality in the speech of the deaf. J. Speech Hear. Res. 11: 553 559(1968). DiCarlo, L.M.: The deaf (Prentice Hall, New York 1964). Emanuel, F.W. and Cotinihan, D.T.: Some characteristics of oral and nasal air flow during plosive consonant production. Cleft Palate J. 7: 249-260 (1970). Ewing, 1. and Ewing, A.: The handicap of deafness (Longmans Green, New York 1946). Fant, G.: Descriptive analysis of the acoustic aspects of speech. Logos 5: 3-17 (1962). Gilbert, H.R.: Oral airflow during stop consonant production. Folia phoniat. 25: 288 301 (1973). Haycock. G.S.: The teaching of speech (The Volta Bureau. Washington 1942). Hudgins, C.V.: A comparative study of the co-ordinations of deaf and normal voice. J. genet. Psychol. 44: 3-46 (1934). Hudgins, C. V. and Numbers. F.C.: An investigation of the intelligibility of the speech of the deaf. Genet. Psychol. Monogr. 25: 289-392 (1942). Lubker, J.F. and Moll, K.L.: Simultaneous oral-nasal flow measurements and cinefluorographic observations during speech production. Cleft Palate J. 2: 257 272 (1965). Martony, J.: Studies on the speech of the deaf. 0- Prog. Status Rep. Speech Transm. Lab. R. Inst. Technol., Stockh. (1965). McClumpha, S.H.: Cinefluorographic investigation of velopharyngeal function in selected deaf speakers; unpubl. MA thesis Gainsville University of Florida (1966). Miller, J.: Speech and the pre-school child. Volta Rev. 62: 315-317 (1960). Numbers, F.C.: Is speech teaching a failure? Volta Rev. 48: 264 265 (1946). Peterson, G.: Influence of voice quality. Volta Rev. 48: 640-641 (1946). Schwab, IP.. Rontgenkinematographische Untersuchungen über die Sprache von Taubstum men. Arch. Ohr.-Nas. KehlkHeilk. 183: 469-471 (1964). Silverman, S.R.: Teaching speech. Proc. 39th Conv. Am. Instr. Deaf, vol. 62, pp. 164 173 (1960). Smith, L.L. and Hutchinson, J.M.: An aerodynamic evaluation of consonant production in the adult deaf. Oral pres. Am. Speech Hear. Ass., Las Vegas 1974. Subtelny, J.D.. Worth, J.H., and Sakuda, M.: Intraoral pressure and rate of flow during speech. J. Speech Hear. Res. 9: 498-578 (1966). Voelker, C.H.: A preliminary stroboscopic study of the speech of the deaf. Am. Ann. Deaf 80: 243-259 (1935). Voelker, C.H.: An experimental study of the comparative rate of utterance of deaf and normal speakers. Am. Ann. Deaf. 83: 274-283 (1938).
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References
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Harvey R. Gilbert, The Pennsylvania State University, Speech and Hearing Clinic, 110 Moore Building, University Park, PA 16802 (USA)
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Voorhees, I. W.: Defects in speech in relation to defects in hearing. Archs Otolar. 31: 7 IS (1940). Warren, D. IV.: Nasal emission of air and velopharyngeal function. Cleft Palate J. 4: 148 156 (1967). Warren, D. and Devereux, J.L.: An analog study of cleft palate speech. Cleft Palate J. 3: 103 114 (1966). Warren, D.W. and Ryon, W.E.: Oral port constriction, nasal resistance, and respiratory aspects of cleft palate speech: an analog study. Cleft Palate J. 4: 38 46 (1967).
Simultaneous Oral and Nasal Airflow during Stop Consonant Production by Hearing-Impaired Speakers H.R. Gilbert Speech Science Laboratory, The Pennsylvania State University, University Park. Pa.
Introduction Characteristics which have been described as typical of hearing-impaired speech include slow rate (Voelker, 1935, 1938; Colton and Cooker, 1968), high pitch (Haycock, 1942; Ewing and Ewing, 1946; Boone, 1966), breathiness (Peterson, 1946; Silverman, 1960), misarticulations (Hudgins, 1934; Hudgins and Numbers, 1942; Silverman, 1960; Calvert, 1963\ D¡Carlo, 1964; Schwab, 1964), nasality (Voorhees, 1940; Haycock, 1942; Hudgins and Numbers, 1942; Numbers, 1946; Peterson, 1946; Miller, 1960; Silverman, 1960), faulty rhythm and faulty intonation patterns (Hudgins and Numbers. 1942; Silverman, 1960; Schwab, 1964). Despite the recognized need for research concerned with the speech of hearing-impaired individuals, only a few researchers (Bensen, 1951; McClumpha, 1966; Smith and Hutchinson, 1974) have used objective measures to study the physiological characteristics of hearing-impaired speech. Two studies have employed airflow-sensing systems, Bensen (1951) who used nasal u-tubes and Smith and Hutchinson (1974) who employed total airflow measure ments. To date, no one has used simultaneous oral and nasal airflows to study the aerodynamics of hearing-impaired speech. It would appear that a system using flow-sensing instrumentation designed to obtain simultaneous oral and nasal airflow measurements during stop conso nant production by hearing-impaired individuals can provide (1) objective data in the form of aerodynamic characteristics of hearing-impaired speech, and (2) a comparison of airflow data obtained from hearing-impaired speakers with avail able data from normally hearing subjects. Accordingly, the present investigation
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Received: September 1, 1975; accepted: September 15, 1975.
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424
was designed to fulfill the above needs through a study of the effects of ( 1) place of articulation (2) voicing, and (3) phonetic context upon simultaneous oral and nasal airflows during production of stop consonants by hearing-impaired speak ers.
Method Instrumentation A large anesthesia mask was modified in order to provide a means for independent channeling of oral and nasal airflows. The mask was divided into oral and nasal chambers by a hard rubber diaphragm which fitted snugly against the upper lip. The regular outlet of the mask served as an opening through which oral airflow was directed to one pneumotachome ter while nasal airflow was channeled to a second pneumotachometer through an outlet drilled into the front wall of the nasal chamber. figure 1 is a block diagram of the instrumentation used in the present study. The general technique used to record volume rate of oral and nasal airflows was similar to the pneumotachographic procedure described by Lubker and Moll (1965). Both oral and nasal airflow rates were determined by systems consisting of (1) a Fleisch pneumotachometer. (2) a Statham model I’M-15 bidirectional differential airpressure transducer, (3) an Accudata model 113 bridge amplifier, (4) a Honeywell M16S0 galvanometer, and (5) a Honeywell model 1508A Visicordcr direct-recording optical oscillo graph. The airflow-sensing systems were calibrated against a rotometer. The system used to sense the speech signal consisted of ( l ) a Grason-Stadlcr model E7300M throat microphone. (2) an Accudata model 120 DC amplifier, (3)3 Honeywell model M1650 galvanometer, and (4) a Honeywell model 1508A Visicorder. The output of this system served as an index of the acoustic onset and cessation of consonants and vowels. Subjects Ten subjects, 5 males and 5 females, ranging in age from L6 to 26 years, participated in the present investigation. All subjects were diagnosed as having moderate to profound bilateral sensorineural hearing losses. The hearing loss in each case was determined to be congenital or onset during the first year of life as ascertained from medical histories. All the hearing-impaired subjects exhibited a minimum hearing loss of 65 dB in the frequencies 500,
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Fig. I. A diagram of the instrumentation used in the present study.
Aerodynamic Characteristics of Hearing-Impaired Speech
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1,000, and 2,000 Hz. The subjects had no other handicap other than the hearing impair ment. The speech of the 10 subjects was rated by 3 teachers of the hearing-impaired and was judged in each case to be typical of hearing-impaired speakers. A further criterion for inclusion in the present study was that each speaker fit into the modified face mask, so that the seals around the edges of the mask and between the oral and nasal chambers were airtight (Lubker and Moll, 1965). Speech Sample The speech sample consisted of isolated syllables constructed so that the sample con tained both voiced and voiceless stop consonants, various places of articulation, and various phonetic contexts in the exploded mode of production. The test phonemes in these syllables were the 6 English stop consonants /p, t, k, b, d, g/, each produced in the pre-, inter-, and postvocalic phonetic contexts in combination with the neutral vowel /A/, i.c. /pAp, ApA/. F.ach of the 12 syllables was produced 3 times in succession with a brief pause between productions / pAp, pAp, pAp/. No attempts were made to change the productions of the speakers. They were asked to produce the utterances to the best of their abilities.
Results
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Oral Airflow Profiles Figures 2 a, b present the characteristic features for the voiced stops and which, in many respects, represent the essential features for the voiceless stops. Figure 2a is an example of a recording of the syllable /dAd/. As may be seen in the oral airflow profile of figure 2 a, an inspiratory flow of small magnitude and short duration is noted prior to the marked rise in flow rate. The next activity is an extremely rapid volume acceleration associated with the prevocalic / d/. Upon reaching a peak value, the flow rate begins a rapid deceleration. As the decelera tion proceeds, it is characterized by rapid a.c. fluctuations in rate of flow which continue through the vowel. Upon cessation of the vowel, the flow rate de creases to zero. The first activity observed in the flow record for the postvocalic Id/ is a marked volume acceleration in a positive direction. Upon attainment of the maximum value, a.c. fluctuations are again noted. The acoustical record shows voicing from the prevocalic consonant through the vowel. Upon cessation of the vowel, voicing ends. Voicing is again noted in association with the post vocalic consonant. Figure 2 b shows a recording of the syllable / AgA/. Many of the features which typify the CVC utterances are also apparent in the VCV oral airflow profiles. As can be seen in figure 2 b, there is a lack of a.c. fluctuations through out the oral airflow trace with a similar lack of voicing continuity in the acous tical record. Voicing is associated with the initial vowel, followed by an interval where no activity in the acoustical record is noted. With the volume acceleration associated with the intervocalic consonant, voicing is again apparent and con tinues through the final vowel.
Gilbert
426
For legend, see p. 428.
Nasal A irflow Profiles Seven subjects consistently exhibited nasal airflows during production of the speech samples studied. 1 subject exhibited only slight nasal airflows asso ciated with the Ipl and /b/ phonemes in the pre- and intervocalic phonetic contexts. 2 subjects showed nasal flows which occurred either during or after cessation of the final phoneme in the sequence. In addition, several different nasal airflow patterns were apparent. These different flow profiles were not mutually exclusive in that one subject may have, and often did, exhibit more than one type of pattern. Figure 2c is a profile of the syllable /pAp/ and illustrates the essential features of the first group of nasal airflow profiles. In this group, peak nasal flows coincide in time with peak oral flows associated with the pre- and post vocalic stops. This general pattern was observed consistently in 7 subjects for/p, t, k/ in the 3 phonetic contexts. For the voiced stop plosives, the number of
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Inspiratory Jluws. Inspiratory or negative flows in the oral flow profiles occurred for 9 of the 10 subjects. These flows were primarily associated with the /k/ and /g/ phonemes occurring somewhat less frequently with It. d, p, b/. These inspiratory flows occurred most often in the pre- and intervocalic phonetic contexts. Only in a few cases were inspiratory flows present in the postvocalic context. The negative flows ranged in value from 0.5 to 9.35 liters/min.
427
subjects exhibiting this pattern varied from 3 for the prevocalic / g/ to 7 subjects for the pre- and postvocalic /b/. As seen in figure 2c, peak oral airflows lead slightly in time peak nasal airflows. The degree to which oral and nasal airflows were out of phase varied with each subject. Figure 2d represents a record of the syllable /kAk/ and is illustrative of a second group of profiles. 4 subjects consistently showed nasal airflows which either coincided with production of the vowel or occurred in the interval be tween the vowel and the postvocalic consonant in the CVC syllable. The first nasal flow activity noted in figure 2d occurs just prior to the rapid volume acceleration in oral flow associated with the prevocalic / k/. Nasal flow activity is again seen during production of the initial consonant with the peak nasal flow occurring sometime after cessation of the vowel. Nasal flow of small magnitude is again observed during the deceleration phase of oral airflow for the postvocalic /k/. This pattern was also observed in VCV syllables associated with either vowel or in the interval between the initial vowel and consonant or between the con sonant and final vowel. The second pattern of nasal flows occurred with equal frequency for both the voiced and voiceless stops. Figures 2e, f are profiles of the syllables /pAp/ and /AtA/, respectively, and illustrate a third group of profiles. This pattern is represented by nasal airflows occurring in conjunction with both the consonant and vowel production in CVC and VCV syllables. The first notable nasal flow activity in the syllable /pAp/
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Aerodynamic Characteristics ot' Hearing-Impaired Speech
Gilbert
428
begins sometime after the attainment of peak oral flow associated with the prevocalic /p/. Peak nasal How occurs at the end of the deceleration phase of the oral airflow associated with the initial consonant. The next nasal flow activity noted occurs towards the end of the vowel production with a final peak nasal flow occurring in conjunction with the postvocalic /p/. In the syllable /AtA/, the first nasal flow activity is associated with the initial vowel. Nasal flow is next noted in conjunction with the intervocalic / 1/. As seen in figure 2 f, peak oral flow associated with / 1/ leads slightly peak nasal flow. The next nasal flow
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Fig. 2. Oral and nasal flow rate profiles and speech signal for the syllables /dAd/ (a), /AgA/ (b), /pAp/ (c), /kA k/ (d), /pAp/ (e), /A tA / (0, and /kAk/ (g).
429
Aerodynamic Characteristics of Hearing-Impaired Speech
Table I. Mean peak oral flow rates (liters/min) and standard deviations presented in rank order of magnitude for the 6 stops in 3 phonetic contexts as produced by the 10 hearing-impaired speakers Prevocalic
Intervocalic
Postvocalic
con sonant
mean * SD
con sonant
mean ± SD
con sonant
mean i SD
in /p/ M /d / M M
91.05 86.22 79.18 57.48 47.24 42.88
N N 111 IM /g/ /b/
86.24 77.65 76.57 54.18 41.91 36.44
ipi /k/ III Idl Isl /w
69.13 67.91 59.72 47.80 41.70 41.09
± 27.17 i 33.87 ± 26.94 i 19.38 ± 16.04 i 19.37
t 28.52 ± 28.69 ± 38.51 t 23.05 i 16.08 t 23.90
± 34.70 t 30.38 ± 27.88 t 20.75 ± 16.22 t 23.28
activity is associated with the final vowel. The nasal flow accelerates slowly during the vowel with a peak flow occurring after cessation of the vowel. This general pattern of profiles occurred most frequently in the CVC paradigm with the voiceless stops. Figure 2 g which is a profile of the syllable / kAk/ shows the essential fea tures of a fourth pattern of nasal airflows exhibited by 2 subjects. Nasal airflows, in this pattern, occurred at utterance end. While nasal airflows may have started during the final phoneme in the sequence, peak (low rate did not occur until sometime after cessation of the final phoneme.
The 0.05 % level of confidence was used in all statistical tests reported in this study.
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Peak Oral Flow Rate Measurements Table I presents the means and standard deviations of the peak oral flow rates for the stops in the 3 phonetic contexts as produced by the speaker group. On the basis of peak oral flow rate, several differences among the stops are clearly evident. Regardless of phonetic context, mean peak oral flow rates were greater for the voiceless stops than for their voiced cognates. With the exception of the It, d/ comparison in the postvocalic phonetic context, each of the voice less stops was accompanied by signigicantly1 greater mean peak oral airflow rates than its voiced cognate. When comparing peak oral flow rates with regard to phonetic context, peak flow rates were greater in the pre- than in the postvocalic phonetic context. Significant differences were found only for /p, t, k/. Peak flow rates were greater in the pre- than in the intervocalic phonetic context. No differences, however,
430
Gilbert
Table II. Mean peak nasal flow rates (liters/min) presented in rank order of magnitude for the 6 stops in 3 phonetic contexts as produced by the 10 hearing-impaired speakers Prevocalic
Postvocalic
Intervocalic
con sonant
n
mean
con sonant
n
mean
con sonant
n
mean
N Ipl M W M l&l
7 8 6 4 7 3
6.34 5.60 5.54 3.12 2.07 1.60
m M Ipl Ibl l&l IV
6 7 8 6 4 5
7.49 5.27 5.18 2.38 2.18 2.01
ipi /k / N 1V l&l
7 6 7 5 4 7
5.97 5.77 5.41 5.75 5.43 3.02
Peak Nasal Flow Rate Measurements Table II presents the mean peak nasal flow rates as produced by the speaker group. No statistical tests were performed on the peak nasal airflow data because the number of subjects contributing to the mean was small and varied for the specific phoneme being produced. However, several patterns were evident from the data presented. With the exception of the /t, d/ comparison in the postvo calic phonetic context, mean peak nasal flow rates were greater for the voiceless stop consonants than for their voiced cognates. This trend was noted for all speakers with only a few exceptions. A comparison of peak nasal airflow rates with respect to phonetic context indicated that, with the exception of /t/, nasal flows were greater in the postvo calic context than in the pre- or intervocalic phonetic contexts. Greater nasal flows were associated with /p, k, d/ in the pre- than in the intervocalic context. While for / 1, b, g/, peak nasal airflows were greater in the inter- than in the prevocalic phonetic context.
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were found to be significant. When the data were compared between the interand postvocalic phonetic contexts, 5 of the 6 consonants exhibited higher mean flow rates in the intervocalic phonetic context. Significant differences were found only for the / 1/. With regard to place of articulation, consonant rank order for the voiceless stops appeared to depend upon phonetic context. Consonant rank order for the voiced stop consonants was invariant across phonetic context. Results of statis tical contrasts within the voiceless category indicated that /t/ had a significantly higher flow rate that /k/ in the prevocalic phonetic context. For the voiced consonants, / d/ was found to exhibit significantly higher flow rates than / b/ in both the pre- and intervocalic phonetic contexts.
Aerodynamic Characteristics of Hearing-Impaired Speech
431
Examining table II with reference to place of articulation, consonant rank order for both the voiceless and voiced stops is dependent upon phonetic con text.
Oral Airflow Profiles Oral flow rate profiles obtained in the present study for the voiced and voiceless stops were similar to those described by Gilbert (1973) who character ized stop consonant production as a three-stage model. The three stages which occurred consecutively were: (1) a reduction in oral flow rate which is related to an increase in vocal tract constriction, (2) a cessation of oral flow associated with an infinite resistance to respiratory flow brought about by a complete closure of the vocal tract at some point, and (3) a marked increase in oral flow which is associated with a rapid opening of the vocal tract. A feature noted by Gilbert (1973) in conjunction with the voiced stops was rapid a.c. fluctuations in the oral flow rate throughout the model. The fluctuations were associated with continuous periods of voicing in the acoustical record and supported the obser vations of Fant (1962) relative to the continuity of vocal cord vibration over a series of voiced sounds. While production of stop consonants by the hearing-impaired speakers con formed to the three-stage model discussed by Gilbert (1973), one unique feature was noted. The feature which was associated with voiced stop production con sisted of a lack of both continuous a.c. fluctuations in the oral airflow record and continuous voicing in the acoustical record. In the CVC paradigm, voicing ended after cessation of the vowel and was not noted again until the onset of the postvocalic consonant. A.c. fluctuations in the flow profile typically were not seen during this interval. In the VCV syllables, voicing and a.c. fluctuations ended after cessation of the initial vowel. Acoustical activity was again noted with the onset of the intervocalic consonant and continued through the final vowel. The lack of continuity of voicing perhaps can be attributed to analytical methods frequently used in teaching speech to hearing-impaired individuals. These methods emphasize mastery of individual phonemes with a gradual com bination of phenemes into meaningful units. These techniques do not stress the timing effects of coarticulation and typically rob the individual’s speech of its naturalness. With regard to inspiratory flows, the present findings support the results reported by Gilbert (1973) that negative flows occurred most often with /k/ and /g/. He attributed these inspiratory flows to posterior movements of the articula tors which bring about volumetric changes in the cavity between the screen of the pneumotachometer and the articulatory structures. In the present study,
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Discussion
con sonant
N Ip/ N
/d / /g /
M
Postvocalic
Intervocalic hearingimpaired mean ±SD
mean
91.05 86.22 79.18 57.48 47.24 42.88
107.33 i 23.48 91.76 ± 24.07 92.05 i 23.79 58.40 t 14.86 38.98 ± 14.40 40.92 ± 14.91
27.17 ± 33.87 i 26.94 ± 19.38 i 16.04 ± 19.37 ±
normals ±
con sonant SD N N Ipl
/d/ iBl lb/
hearingimpaired mean ± SD
normals
86.24 t 28.52 77.65 + 28.69 76.57 < 38.51 54.18 * 23.05 41.91 ± 16.08 36.44 ± 23.90
85.74 t 28.14 74.42 ± 26.90 75.98 ± 27.85 44.31 i 13.45 31.38 -t 12.53 34.42 i 12.21
mean
±
con sonant SD ip i /k /
N /d /
/g/ Ibl
hearingimpaired mean ± SD
normals
69.13 i 34.70 67.91 ± 30.38 59.72 * 27.88 47.80 ± 20.75 41.70 ± 16.22 41.09 t 23.28
77.57 i 29.99 61.08 * 23.70 75.55 i 29.02 36.12 i 13.57 31.71 i 11.51 32.12 ± 13.94
mean
t
SD
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Prevocalic
Gilbert
Table III. A comparison of mean peak oral How rates (liters/min) and standard deviations for the 6 stops in 3 phonetic contexts as produced by the 10 hearing-impaired speakers with those values reported by Gilbert (1973) for 9 normally hearing speakers
Aerodynamic Characteristics of Hearing-Impaired Speech
433
inspiratory flows did not occur as frequently nor were they as great in magni tude as those negative Hows obtained by Gilbert (1973) from a normally hearing population. A possible explanation for the difference in results may be due to the speaker group studied. From the nature of the negative flows obtained, it would appear that posterior movements of the articulators in the hearing-im paired speakers were more restricted than in the normally hearing population, resulting in fewer negative Hows and negative (lows of smaller magnitudes. It is clear, however, that the airflow records of the present study provided only indirect information about articulatory events. As a consequence, further infor mation concerning articulator motility in hearing-impaired speakers must await further study.
Peak Airflow Rates Table III compares the mean peak oral airflow rates and standard deviations for the hearing-impaired subjects in the present study and the values reported by
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Nasal A irflow Profiles Nasal airflows consistently occurred during the test syllables as produced by 7 of the 10 hearing-impaired subjects. 1 subject exhibited only slight nasal flows, while for 2 subjects nasal airflows occurred during the last phoneme in the syllable or at utterance end. When the nasal airflow profiles of the 10 subjects were examined, a number of different nasal airflow patterns were evident. These findings support the cinefluorographic observations of McClumpha (1966) who found considerable variation among deaf speakers in both extent and duration of velopharyngeal function. In the 5 deaf speakers studied by AlcClump ha, velo pharyngeal function ranged from no closure on the speech samples studied to function similar to that of normals. The nasal airflow profiles obtained in the present study support the hypothesis that hearing-impaired speakers represent a heterogeneous population with regard to velopharyngeal function. In several subjects, peak nasal flows associated with both stop consonant and vowel production did not coincide with peak oral flows. In both cases, it appeared that peak oral airflows lead in time the peak nasal airflows. It was also evident from the profiles that peak nasal flows occurred during the closure phase of stop consonant production where no oral flow was observed or occurred after cessation of a phoneme at utterance end. The nasal flow profiles obtained in the present study may reflect an inability of the hearing-impaired speaker to coor dinate velopharyngeal function with the activity of other speech articulators. Martony (1965), in an attempt to specify differences in the speech of normally hearing and deaf boys between the ages of 13 and 15, found abnormal and misplaced nasalization of vowels and too early denasalization of nasal conso nants. His findings clearly indicated that one of the characteristics of hearingimpaired speech was a lack of coordination among articulators.
434
1
■
1
- M wM^cn
aioo-
_ol o1 o1 o]__o1__o1_o_1_o_1_o_1_o_1_o1
Gilben
IU Ipt
/k/ /d/
Ptevocalic
11 Iql Ibl
l \ l /k7 /p/ /d/ /g/ /b/
Intervocalic
Postvocahc
Gilbert (1973) for normally hearing subjects. The mean values in table 111 are also graphically portrayed in figure 3. The peak oral airflows are remarkably similar for the two groups of subjects. In the prevocalic phonetic context, the normally hearing subjects exhibited greater peak Hows for /t. p, k. d/, while the hearing-impaired subjects showed somewhat higher Hows for /g, b/. The hearingimpaired subjects showed somewhat higher mean peak oral airflows for all the phonemes in the intervocalic phonetic context. Ir. the postvocalic phonetic con text, greater peak flows for /k. d, g, b/ were exhibited by the hearing-impaired speakers, while the normal speakers exhibited higher oral flows for /p, t/. The peak oral airflows obtained in the present study were greater than those values reported by Emanuel and Counihan (1970) for normal subjects. They used a divided face mask with two warm wire anemometers to assess simulta neous oral and nasal airflows. Those studies which have used warm-wire anemometry to assess airflow events (Subtelny el al., 1966; Emanuel and Counihan
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Fig. 3. A graphic representation of mean peak oral now rate values (liters/min) during production of the 6 stop consonants in 3 phonetic contexts as produced by the 9 normally hearing speakers (■) reported by Gilbert (1973) and 10 hearing-impaired speakers O') ob tained from the present study.
Aerodynamic Characteristics of Hearing-Impaired Speech
435
1970) have consistently reported peak flow rates well below values reported in studies where face mask-pneumotachographic procedures were used. Subtelny et al. (1966) have attributed these differences to an increased effort required to overcome resistance imposed by the face mask. Emanuel and Counihan (1970) used a face mask and reported peak flow values for stop consonant production which were less than those reported by Gilbert (1973) for normal subjects. It appears that the difference in basic flow instrumentation rather than the use of a face mask may account for the differences in peak flows obtained by Emanuel and Counihan (1970) and those reported by Gilbert (1973) and flow values reported in the present study. Smith and Hutchison (1974) reported total airflow rates for stop consonant production by an adult hearing-impaired population that were lower in magni tude than the peak oral airflows obtained in the present investigation. Since airtight velopharyngeal closure may not occur during the speech of hearing-im paired individuals, the total flow measurements may not represent only oral articulatory events. With regard to peak nasal flow rates, Lubker and Moll (1965) observed from a normally hearing subject only slight nasal flows preceding or coincidental with the initiation of phonation during production of non-sense syllables. Emanuel and Counihan (1972) reported peak nasal flow rates for stop consonants be tween 0.12 to 1.54 liters/min for their normally hearing subjects. Warren (1967) reported that cleft-palate speakers with velopharyngeal inadequacy exhibited nasal flow rates greater than 10.5 liters/min. Peak nasal airflows obtained in the present investigation ranged from 0.57 to 21.45 liters/min. Mean peak nasal airflows (table II) for the hearing-impaired speakers were between those values reported for normals and nasal airflows reported for cleft-palate speakers with velopharyngeal inadequacy. The nasal flow patterns and peak nasal airflows obtained in the present study may not solely reflect velopharyngeal function. Research has shown that nasal airflows are also dependent upon size of oral port constriction {Lubker and Moll, 1965; Warren and Ryon, 1967), nasal resistance and respiratory effort (Warren and Devereux, 1966; Warren and Ryon, 1967). Furthermore, while the airflow-sensing system used in the present study has certain limitations (Lubker and Moll, 1965; and Gilbert, 1973) and by itself may not be sufficient to describe articulatory events, the simultaneous oral and nasal airflows provided appear to be of importance in specifying certain aerodynamic characteristics heretofore not studied in the speech of hearing-impaired individuals.
Simultaneous oral and nasal airflows were obtained from a group of moderately to profoundly hearing-impaired young adults during production of the stop consonants /p, t, k,
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Summary
Gilbert
436
b, d, g/. Both oral and nasal airflow profiles as well as peak oral and nasal airflows are presented. Oral airflows were similar to those obtained from normally hearing subjects. Several different nasal airflow patterns were observed which suggest that the hearing-im paired population is heterogeneous with regard to velopharyngeal function.
Bensen, J.: An experimental study of the relationship between the amount of nasal emission of air and judged nasality; unpubl. MA thesis Morgantown West Virginia University (1951). Boone, D.R.: Modification of the voices of deaf children. Volta Rev. 68: 686 692 (1966). Calvert, D.R.: An approach to the study of deaf speech. Proc. 41st Conv. Am. Instr. Deaf, vol. 65, pp. 242 245 (1963). Colton, R.H. and Cooker, H.S.: Perceived nasality in the speech of the deaf. J. Speech Hear. Res. 11: 553 559(1968). DiCarlo, L.M.: The deaf (Prentice Hall, New York 1964). Emanuel, F.W. and Cotinihan, D.T.: Some characteristics of oral and nasal air flow during plosive consonant production. Cleft Palate J. 7: 249-260 (1970). Ewing, 1. and Ewing, A.: The handicap of deafness (Longmans Green, New York 1946). Fant, G.: Descriptive analysis of the acoustic aspects of speech. Logos 5: 3-17 (1962). Gilbert, H.R.: Oral airflow during stop consonant production. Folia phoniat. 25: 288 301 (1973). Haycock. G.S.: The teaching of speech (The Volta Bureau. Washington 1942). Hudgins, C.V.: A comparative study of the co-ordinations of deaf and normal voice. J. genet. Psychol. 44: 3-46 (1934). Hudgins, C. V. and Numbers. F.C.: An investigation of the intelligibility of the speech of the deaf. Genet. Psychol. Monogr. 25: 289-392 (1942). Lubker, J.F. and Moll, K.L.: Simultaneous oral-nasal flow measurements and cinefluorographic observations during speech production. Cleft Palate J. 2: 257 272 (1965). Martony, J.: Studies on the speech of the deaf. 0- Prog. Status Rep. Speech Transm. Lab. R. Inst. Technol., Stockh. (1965). McClumpha, S.H.: Cinefluorographic investigation of velopharyngeal function in selected deaf speakers; unpubl. MA thesis Gainsville University of Florida (1966). Miller, J.: Speech and the pre-school child. Volta Rev. 62: 315-317 (1960). Numbers, F.C.: Is speech teaching a failure? Volta Rev. 48: 264 265 (1946). Peterson, G.: Influence of voice quality. Volta Rev. 48: 640-641 (1946). Schwab, IP.. Rontgenkinematographische Untersuchungen über die Sprache von Taubstum men. Arch. Ohr.-Nas. KehlkHeilk. 183: 469-471 (1964). Silverman, S.R.: Teaching speech. Proc. 39th Conv. Am. Instr. Deaf, vol. 62, pp. 164 173 (1960). Smith, L.L. and Hutchinson, J.M.: An aerodynamic evaluation of consonant production in the adult deaf. Oral pres. Am. Speech Hear. Ass., Las Vegas 1974. Subtelny, J.D.. Worth, J.H., and Sakuda, M.: Intraoral pressure and rate of flow during speech. J. Speech Hear. Res. 9: 498-578 (1966). Voelker, C.H.: A preliminary stroboscopic study of the speech of the deaf. Am. Ann. Deaf 80: 243-259 (1935). Voelker, C.H.: An experimental study of the comparative rate of utterance of deaf and normal speakers. Am. Ann. Deaf. 83: 274-283 (1938).
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References
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Harvey R. Gilbert, The Pennsylvania State University, Speech and Hearing Clinic, 110 Moore Building, University Park, PA 16802 (USA)
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Voorhees, I. W.: Defects in speech in relation to defects in hearing. Archs Otolar. 31: 7 IS (1940). Warren, D. IV.: Nasal emission of air and velopharyngeal function. Cleft Palate J. 4: 148 156 (1967). Warren, D. and Devereux, J.L.: An analog study of cleft palate speech. Cleft Palate J. 3: 103 114 (1966). Warren, D.W. and Ryon, W.E.: Oral port constriction, nasal resistance, and respiratory aspects of cleft palate speech: an analog study. Cleft Palate J. 4: 38 46 (1967).
