Influence of Mizo Language on Nasal and Oral Passage in English: a Nasometric Study
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INFLUENCE OF MIZO LANGUAGE ON NASAL AND ORAL PASSAGE IN ENGLISH: A NASOMETRIC STUDY Meenu Kalyani1, Ashok Kumar Sinha2, Himanshu Kumar3, Bibhu Prasad Hota4, Lorna Das5 1(Speech and language pathologist & Audiologist, Kolkata, India) 2(Director, AYJNIHH, Mumbai, India) 3(Lecturer (Speech & Hearing), AYJNIHH, ERC, Kolkata, India) 4(Lecturer (Speech & Hearing), AYJNIHH, ERC, Kolkata, India) 5(Post graduate trainee in Audiology and Speech Language Pathology, AYJNIHH, ERC, Kolkata, India)
ABSTRACT
Nasometer is computer based instrument which facilitates accurate signal
analysis, which yields “nasalance” score. The nasality measure is derived from the ratio
of acoustic energy output from the nasal and oral cavities of the speaker.
Most research reports on normative nasalance score of English language. There is
no report regarding nasalance score variance in the Mizo language speakers speaking
English. The study aims in establishing norms and measuring nasalance score in Mizo
speakers reading English passages.
A total of 30 subjects (15 males and 15 females) who are native speakers of Mizo
language who has exposure of English language since childhood were selected.
Nasometer II Model 6400 (Software version 2.6) of Key Elemetrics Corporation
was used.
1 Three standardized passages (Zoo passage, Rainbow passage and nasal sentences)
were used for the study.
The mean nasalance scores obtained for zoo, rainbow and nasal sentences in
female and male were 15.93 ± 3.15 SD, 35.60 ± 3.05 SD, 64.33 ± 3.26 SD and 18.26 ±
3.53 SD, 33.13 ± 1.68 SD, 63.20 ± 88 SD respectively.Standard norms shows significant
differences between male and female for Zoo and Rainbow Passages but not in Nasal
Sentences.
Keywords: Mizo Language, Nasometer, Nasalance score, Zoo Passages, Rainbow Passages
INTRODUCTION
Verbal communication is one of the most important models to communicate
between the human beings. The main elements of the verbal communication are hearing,
voice; language and speaking are mainly created through the harmonious functioning of
respiration, phonation, resonance, and articulatory muscles together. Resonance modifies
voice by increasing or decreasing the harmonics of voice. The resonator system has a
complex structure. Supraglottal air gaps act as resonators. These are complex air gaps
which are found in the tight area that goes through the larynx, the large opening of the
larynx, the wide cavity in the mouth and nasal cavity. Normal speech sound production
depends on the ability to rapidly couple and decouple the nasal cavity from the oral
cavity. Nasal speech sound require oral nasal coupling and oral sounds require oral-nasal
decoupling. The process of coupling and decoupling the oral and nasal cavities for speech
2 is called velopharyngeal valving. This valving is controlled by the elevation of the velum
and constriction of the pharyngeal walls.
Role of velopharyngeal mechanism in speech production
Velopharyngeal mechanism varies the degree of acoustic coupling between the
oral and nasal cavities. Inadequate closure of the velopharyngeal mechanism may result
in nasalized speech or the inability to impound air pressure within the oral cavity for the
production of consonants. Unvoiced consonants may become voiced, plosives become
snorts, and vowels exhibit an unmistakable nasal quality or twang. Inappropriate or
excessive velopharyngeal closure can result in the familiar “stuffy nose” quality.
Adequacy of velopharyngeal closure and appropriate timing of the valving action are two
important parameters of articulation. Closure is achieved by elevating and retracting the
soft palate and at the same time constricting the walls of the nasopharynx. The posterior
pharyngeal wall may move anteriorly to meet the soft palate in some individuals and may
be seen as a compensatory gesture in instances of a short palate (Zemlin, 1988).
Movement of velum is essentials for making the distinction between oral and nasal
sounds in speech.
Five muscles are involved in the velar functions which are levator veli
palatine, uvular muscles, tensor veli palatine, palatopharyngeous, and palatoglossus.
Elevation of velum is primarily contraction of the lavetor veli palatine muscles (Kent,
1997; Seikel et al 2000, Zemlin, 1998). Velopharyngeal closure is accomplished by the
coordinated movement of all of above structures.
3 Velopharyngeal closure pattern in female are in coronal pattern 19(35.85)%,
circular 15 (28.30)%, circular with passavant’s ridge 11 (20.75)%, and sagittal 8
(15.09)% where as in the male the frequency is with coronal pattern 14(38.89)%, circular
15 (41.67)%, circular with passavant’s ridge 3 (8.33)%, and in sagittal 4 (11.11)%.
Velopharyngeal closure occurs not only for speech, but also for other pneumatic
activities such as sucking, blowing, and whistling and non-pneumatic activities such as
gagging, swallowing, and vomiting. The position and degree of closure differ for all these
activities. The point of contact and degree of closure even vary different phonemes and
with different phonetic environments. (Moll, 1962; Shprintzen et al., 1975). Closure may
be completely for pneumatic activities but insufficient for speech or other pneumatic
activities (Shprintzen et al., 1975).
The term nasalance has been proposed by Fletcher and Frost, 1974 for a measure
of velopharyngeal closure during voiced speech in which nasally emitted acoustic energy
is compared to the orally emitted energy. Nasometer is developed by Samuel Fletcher,
Larry Adams, and Martin McCutcheon at the University of Alabama at Birmingham,
Biocommunications Department (1989). Since the introduction nasometer has been
utilized by a number of investigators in an attempt to determine its utility in the
assessment and treatment of patients at risk for manifesting velopharyngeal impairment.
The Nasometer has provided an easy, non-invasive method for assessing nasality
objectively.
Nasometer is computer based instrument employs microphones on other side of a
sound separator plate which rests on the upper lip. The nasality measure is derived from
4 the ratio of acoustic energy output from the nasal and oral cavities of the speaker. Using
an innovative input device consisting of a directional microphone mounted on either side
of an efficient sound separator plate the Nasometer headset facilitates accurate signal
analysis, which yields a “nasalance” score. The signal from each microphone is filtered
and digitized by custom electronic modules. The data are then processed by a computer
and accompanying software.
A numeric ratio of nasal acoustic energy to the sum of nasal plus oral acoustic
energy is calculated, multiplied by 100 and expressed as a “nasalance score” that is (N/
(N+O)) x 100 = Nasalance) and is displayed graphically on the host computer screen in
real time.
The output of this instrument provides the user with a score that reflects the
relative amount of nasal acoustic energy in a subject’s speech. Standardized nasometry
scores have been published in several languages such as English (Seaver et al., 1991, van
Doorn& Purcell, 1998); Flemish (Van Lierde et al., 2001); Thai (Prathanee et al., 2003).
The nasalance score is a valid correlate of perceived nasality (Fletcher, 1976), has a high
specificity (86%), a high sensitivity (87%), and a high overall all efficiency (87%)
(Dalston et al., 1993). Nasalance score has a limited implication for cross-country or
cross-language comparison because interpretation for identifying normal and abnormal
based on the cutoff scores. Therefore, it should be a supplementary but not a substitute
for clinical judgment (Vallino-Napoli and Montgomery 1997).
The Mizo language, or Mizo tawang, is spoken natively by the Mizo people in the
Mizoram state of India, Chin State in Burma, and the Chittagong Hill Tracts of
5 Bangladesh. The language is also known as Lushai, a colonial term, as the Lushei people
were the first to have external exposure. The Mizo language belongs to the Kukish
branch of the Tibeto-Burman family of languages. The numerous clans of the Mizo had
respective dialects, amongst which the Lushei (Lusei, by Mizo) dialect was most
common, and which subsequently became the Mizo language and the lingua franca of the
Kuki people due to its extensive and exclusive use by the Christian missionaries. Mizo
language has eight tones and intonations for each of the vowels /a/, /aw/, /e/, /i/ and /u/,
four of which are reduced tones and the other four long tones.
Tone systems have developed independently in many of the daughter languages
largely through simplifications in the set of possible syllable-final and syllable-initial
consonants. Typically, a distinction between voiceless and voiced initial consonants is
replaced by a distinction between high and low tone, while falling and rising tones
developed from syllable-final h, a glottal stop, which themselves often reflect earlier
consonants. In tone languages there are potential conflicts in the perception of lexical
tone and intonation, as both depend mainly on the differences in fundamental frequency
(F0) patterns.
It is well established that differences in nasalance scores occur among different
native languages. The frequency of phonemic distribution varies in different language.
The distribution of phonemes is different in different languages; standard passage for
each language should be developed. The corresponding normative nasalance scores
should be computed for each languages or regional dialect (Seaver et al., 1991) because
vowels are intentionally nasalized in some language (e.g., French) and some regional
dialect, for instances, English Phonetician often described the vowel in American English
6 dialects as more nasalized then the same vowel in queen’s English. For American English
(Flecther et al., 1989), Australian English (van Droon& Purcell, 1998), German (Heppt et
al., 1989), Castilian Spanish (Santosh Terron et al., 1991), Finnish (Happannen, 1991)
and Midwest Japanese (Tachimura& Mori, 2000) these normative nasalance score have
been computed.
AIM OF THE STUDY
Most research reports on normative nasalance score were made on the basis of
English language. There is no report regarding nasalance score variance in the Mizo
language speakers speaking English. From the review it is evident that nasal resonance
varies in speech sound of different language and in different dialects of same language. In
multilingual country like India where English is spoken as second or third language, the
nasalance score as measure from the zoo passage, rainbow passage and nasal sentences
might have to be interpreted differently. The study aims in establishing norms and
measuring nasalance score in Mizo speakers reading English passages.
METHODOLOGY
Participants
Native speakers of Mizo language with second language as English were selected
for the study. A total of 30 subjects comprising 15 male and 15 female were divided into
two groups. Group-I had 15 female native speakers of Mizo language and group-II had
15 male native speakers of Mizo language. The mean and standard deviation of the
7 subjects age was 21.3 and 1.79for male and for female 21.6 and 1.59 respectively. The
age ranges of all the subjects were between 18 to 30 years.
SUBJECT SELECTION CRITERIA
Inclusion criteria
All the subjects were native speaker of Mizo language, able to read English fluently and
within the age range of 18 to 30 years and willing to participate in the study.
Exclusion criteria
All the participants having any speech and language problem, perceived resonance
disorder, suffering from cold or other upper respiratory tract infections, and any hearing
problem were excluded from the study.
Instrumentation and test environment
Nasometer II Model 6400 (software version 2.6) of Key Elemetrics Corporation
was connected to a desktop computer model (HCL Pentium 4) was used for measurement
of mean nasalance in this study. Nasometer was housed in a quiet room which was
partially acoustically treated in the clinic of AYJNIHH, ERC, KOLKATA.
INSTRUCTIONS
Verbal instructions were given in English. The instruction was “Three texts will
appear on the screen. Read the text which appears on the screen exactly as it appears-‘Do
not repeat the text or add anything which does not appear on the screen’. Three trials will
be taken for each passage”. The subjects were instructed to start reading after the
8 recording icon was clicked. Nasalance measure was taken first for oral passage and, then
for oral nasal passage and then for nasal sentences. The subjects were instructed not to
repeat a syllable once spoken, and also not to add filters like /umm, or /aaa/ in between.
However, the subjects were allowed to pause in between reading, but to resume reading
from where they stopped.
READING STIMULI
For measurement of mean nasalance and in variance three standardized passage will be
used for the study.
1. The zoo passage (Fletcher, 1972)
2. The rainbow passage (Fairbanks, 1960)
3. A set of 5 nasal sentences (Fletcher, 1978)
TESTS
Three standardized passages for the measurements of nasalance were used. Zoo
passage given by Fletcher (1972) which excluded nasal consonants in English language
was used. Rainbow passage developed by Fairbanks (1960) containing 11.5% nasal
consonants in English language were used in the study. A set of five nasal sentences were
taken from the manual of nasometer II which contained 35% nasal consonants in English
were used. This was more than three times as many as would be expected in standard
American English sentences (Fletcher, 1978).
9 PROCEDURE
The nasometer II model 6400 was calibrated using the standard calibration
procedure provided by the manufacturer prior to data collection. At the beginning of each
data collection session, the nasometer was calibrated in accordance with manufacturer
instructions. The nasometer headpiece was then positioned such that the oral and nasal
microphones were at equivalent distances from the mouth and nose. The subject was
seated in front of a computer monitor and asked to read the Zoo passage, Rainbow
passage and Nasal sentences with normal loudness and at a normal rate of speech. The
proper placement of headset on a subject has been shown. All the subjects were given
instruction prior to the test.All subjects were given three trials. Average mean nasalance
scores were computed for statistical analysis. It took about 15 minutes to test each
subject.
RESULTS
COMPARISON OF MEAN NASALANCE ACROSS THE PASSAGES
Mean nasalance for zoo passage, rainbow passage, and nasal sentences
All subjects were asked to read passage and scores of mean nasalance were analyzed.
Mean and standard deviation of mean nasalance for the Zoo passage, rainbow passage,
and nasal sentences were computed and are reported in Table 1 for group-I and group-II.
10 Table.1: Mean and standard deviation of mean nasalance score of group I and group II as
measured on Zoo Passage, rainbow passage and nasal sentences.
Passage Group- I (Female) Group – II (Male) Zoo passage Mean 15.93 18.26 SD 3.15 3.53 Rainbow passage Mean 35.60 33.13 SD 3.05 1.68 Nasal sentences Mean 64.33 63.20 SD 3.26 2.88
DIFFERENCES OF MEAN NASALANCE BETWEEN THE PASSAGES
Differences of mean nasalance between the Zoo Passage and Nasal Sentences, Rainbow
Passage and Nasal Sentences, Rainbow Passage and Zoo Passage
The difference in mean and standard deviation of mean nasalance scores of group-I and
group-II subjects taken together were computed and reported in table 2 between Zoo
Passage and Nasal Sentences,Rainbow Passage and Nasal Sentences, Rainbow Passage
and Zoo Passage.
11 Table.2: Mean and standard deviation of mean nasalance score for Zoo Passage and Nasal
Sentences, Rainbow Passage and Nasal Sentences, Rainbow Passage and Zoo Passage
Passage N Mean Standard deviation Nasal sentences 30 63.76 3.08 Zoo Passage 30 17.10 3.49 Diff (1-2) 46.66 3.29 Nasal sentences 30 63.76 3.08 Rainbow passage 30 34.36 2.73 Diff (1-2) 29.40 2.91 Rainbow passage 30 34.36 2.73 Zoo passage 30 17.10 3.49 Diff (1-2) 17.26 3.13
The Degree of freedom and t-value of comparison of means for Zoo Passage and Nasal
Sentences, Rainbow Passage and Nasal Sentences, Rainbow Passage and Zoo Passage.
Table.3: comparison of means for Zoo Passage and Nasal Sentences, Rainbow Passage and
Nasal Sentences, Rainbow Passage and Zoo Passage.
Passages Variances Df t value Pr> /t/ ZooPassage Equal 58 54.84 <.0001 And Nasal Sentences Unequal 57.09 54.84 <.0001
Rainbow Passage Equal 58 39.08 <.0001 and Nasal Sentences Unequal 57.19 39.08 <.0001
Rainbow Passage Equal 58 21.30 <.0001 and Zoo Passage Unequal 57.19 21.30 <.0001
12 Nasalance scores along with Gender Differences
All the subjects were asked to read all three passages and the observations were
combined for female and male separately of normal Mizo speakers and mean and
standard deviation of female and male were found to be 38.622 and 38.200 respectively.
Table.4: Mean and Standard deviation of gender differences
Gender Observation Mean Standard Deviation Female 45 38.622 20.33
Male 45 38.200 19.09
Diff (1-2) 0.422 19.72
The degree of freedom and t-value of comparison of means of gender differences.
Table.5: Comparison of means of gender differences
Variances Df t-Value Pr>/t/ Equal 88 0.10 0.91
Unequal 87.65 0.10 0.91
13 Computation of t test
For examining the gender difference of the mean nasalance of the native speakers of
Mizo language, t test was computed and the summary of equality of mean nasalance has
been reported in Table 6
Table.6: Summary of equality of mean nasalance of Mizo speakers speaks English language as
second language.
t- test for Equality of means df Sig.(2tailed) Zoo Passage
Equal variance assumed 2.731 28 .011
Equal variance not assumed. 2.731 21.748 .012 Rainbow Passage
Equal variance assumed -1.909 28 .067
Equal variance not assumed -1.909 27.636 .067
Nasal Passage
Equal variance assumed 1.007 28 0.322
Equal variance not assumed 1.007 27.57 0.322
14 Table.7:.Mean and standard deviation of male, female, male + female and standard norms across the passages.
STANDARD MALE FEMALE MALE+FEM NORMS ALE PASSAGE MEAN MEAN MEAN MEAN S.D ZOO 18.26 15.93 17.1 11.25 5.63 PASSAGE
RAINBOW 33.13 35.60 34.36 31.47 6.65 PASSAGE NASAL 63.20 64.33 63.76 59.55 7.96 SENTENCES
t-value and degree of freedom of the Zoo Passage between male and female and male and
female together combined.
Table.8: t-value and degree of freedom of the Zoo Passage
t-Value df Observed Value Male 4.0857 8.48 1.860 Female 2.8192 7.92 1.860 Male+ Female 4.8375 33.33 1.697
t-value and degree of freedom of the Rainbow Passage between male and female and
male and female together combined.
Table.9: t-value and degree of freedom of the Rainbow Passage.
t-value df Observed Value Male 0.9373 5.03 2.015 Female 2.1851 5.50 2.015 Male+ Female 2.2020 22.36 1.717
15 t-value and degree of freedom of the Nasal Sentences between male and female and male
and female together combined.
Table.10: t-value and degree of freedom of the Nasal Sentences
t-Value df Observed Value Male 1.6700 3.68 2.353 Female 2.1522 3.76 2.132 Male+ Female 2.7018 15.44 1.750
DISCUSSION
The purpose of this study is to develop to find out normative nasalance scores for
native Mizo language speaker speaking English as second language since school age for
different stimuli (Zoo Passage, Rainbow Passage and Nasal Sentences) as compared with
the normative data for the English speakers as measured by the Nasometer-II of Kay
Elemetrics Corporation. Gender differences in measures of mean nasalance were also
studied. Results of the statistical analysis were presented in the previous chapter.
Mean Nasalance of native speakers of Mizo
The mean nasalance scores and standard deviation of the native speakers (both
male and female) of the Mizo was obtained. As native speakers of Mizo were reading
English Passages containing no nasal sounds, 11.5% of nasal sounds and 35.5% of nasal
sounds in Zoo, Rainbow and Nasal Sentences, clearly shows significant differences in
nasalance score for Zoo Passage as compared to the normative data of the native English
speaker.
16 The t value of Rainbow Passage for female group, for male group and
for both combined male and female group shows significant differences in mean
nasalance scores as shown in the table 9.The t test of Nasal Sentences shows significant
differences for female group and for both combined male and female group. But there is
no significant differences in the male group.
Figure 1.Comparison of female and male nasalance scores on Zoo Passage,
Rainbow Passage, and Nasal Sentences
Figure 1.Shows passages on X-axis and nasal percentage on the y-axis and shows
significant nasal differences between female and male.
The main difference between nasal and oral vowels is due to the position of the
soft palate. During the articulation of nasal vowels, the soft palate is lowered down, so
that the air stream is free is free to pass not only through the buccal cavity but also
through the nasal cavities. Due to the coupling of the buccal and nasal cavities, the first
formant of all nasal vowels is slightly reduced in intensity. Generally speaking, the nasal
vowels are in the same articulatory position as the corresponding oral vowels (Ferguson
and Chowdhury, 1960).
Mizo language has eight tones and intonations for each of the vowels /a/, /aw/, /e/,
/i/ and /u/, four of which are reduced tones and the other four long tones. The vowel /o/
has only three tones, all of them of the reduced type; it has almost exactly the same sound
17 as the diphthong /oƱ/ found in American English. Mizo is a tonal language, in which
differences in pitch and pitch contour can change the meanings of words.
Most of the studies assert that higher nasalance in adult females can be attributed
to higher average pitch levels (Britto& Doyle, 1990) and the use of greater pitch
variability (Sulter& Peters, 1996).Female also use different intonation patterns (Elyan,
1988) and voice markers for resonance, loudness, and voice quality (Oates &Dacakis,
1997) in their speech.
The mechanism for velopharyngeal valving has been found to differ in male and
female. McKerns and BZoch (1970) investigated the mechanism for velopharyngeal
valving in 40 normal young adults (20 male & 20 female), using lateral cinefluorography,
and found significant differences between the genders. The basic orientation of velum to
pharynx in male can be described in terms of an acute angle and that of female more
approximately in terms of a right angle. The velar length is greater in male, the height of
elevation is greater, the contact is less, and the inferior point of contact is most usually
above palate plane. In females the above pattern is reversed.
Nasalance Scores: Gender Difference
There is no significant difference between the female and male
group as shown in the table 4 and 5. The t test for Equality of means of the Zoo Passages
and Rainbow Passage shows significant differences except for Nasal Sentences shown in
the table 6.
Study conducted by Dalston, (1991); Anderson, (1996); Neiman, and Gonzalez-
Landa, (1993); Seaver, Dalston, Leeper and Adams (1991); Thomas and Hixon, (1979);
18 and Seaver et al (1991) indicated the gender differences in the mean nasalance scores
with higher nasalance scores for female. Researchers have observed that female speakers
had significantly higher nasalance scores than male subjects on nasal sentences. This
could be due to the nasal airflow which is higher in females (Thomas and Hixon, 1979).
Also this may be due to the increased respiratory effort and increased nasal cross-section
area. One more explanation for the gender difference in nasalance scores was the
disparity might be due to the differences in nasal cross-section area and modal pitch.
Nasal cross-section area and F0 was evaluated using modification of theoretical hydraulic
principle and visipitch respectively. Seaver et al (1991) study found significant
differences in nasal cross-section areas and modal pitch between male and female
subjects.
There have been studies focused on sex difference in nasalance scores. Some
studies reported no sex differences in nasalance scores during reading of the Zoo passage
(Seaver et al., 1991; Leeper et al., 1992; Litzaw and Dalston, 1992; Mayo et al., 1996;
van Droon and Purcell, 1998), but others indicates higher nasalance scores among women
during reading of the nasal passage (Seaver et al., 1991; Vallino-Napoli and
Montgomery, 1997). That is although it is possible that sex differences in nasalance
scores are related to the test stimulus, it is not clear whether the findings obtained among
non-Japanese speakers are also valid for Japanese speakers which has different
phonological characteristics from Western Languages.
Gender related differences in nasalance values have been related to basic
anatomical structural and physiological differences between males and females. The
resonance of voice is influenced by the size, shape, and surface of the infraglottal and
19 supraglottall resonating structure and cavities (Shprintzen&Bardach, 1995). Various
studies have reported that the functioning of larynx and velopharynx is affected by a large
number of anatomical, physiological, and aerodynamical gender realted differences.
Physical size appears to be the predominant anatomical feature that differentiates male
and female larynges (Gooze’e et al., 1998 &Kahane, 1983).
Comparison on mean nasalance across the passages
Paired t-test was done to find out the differences in nasalance score between
Nasal sentences and Zoo Passages. The resulted depicted significant difference in mean
nasalancescores of Nasal Sentences and Zoo passage for all 30 subjects, Nasal Sentences
showed higher nasalance score as compared to Zoo passage as shown in the table 3.
The mean of nasal sentences and rainbow passages were calculated to find
out the mean nasalance. Significant differences were found between the nasal sentences
and Rainbow passage has been shown in the table 3. Thus the results indicate higher
nasalance values for Nasal Sentences.
The mean of Rainbow passage and Zoo Passage were calculated to
find out comparison of mean nasalance. Higher significant difference of nasalance for
Rainbow Passage as compared to the Zoo Passage as shown in the table 3.
CONCLUSION
The present study was taken up with the purpose of investigating the norms for
mean nasalance as measured by Zoo, Rainbow, and Nasal Sentences for the native
20 speakers of the Mizo language. The reported normative nasalance data will provide
important reference information for several clinicians who assess resonance disorders.
Speech pathologists can measure the effects of a specific therapy approach, and the
plastic surgeon can evaluate the effects of different nasal and pharyngeal surgical
techniques.
The normative scores can be used for assessment of different resonance disorders like:
-Cleft lip and Palate
-Motor Speech Disorder
-Hearing Impairment
-Functional Nasality Problems
-Singing Pedagogy
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