Influence of Mizo Language on Nasal and Oral Passage in English: a Nasometric Study

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)ABSTRACTNasometer 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 speakingEnglish. 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 NasalSentences.Keywords: Mizo Language, Nasometer, Nasalance score, Zoo Passages, Rainbow PassagesINTRODUCTIONVerbal 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 speech2 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)%, circular15 (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 from4 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, vanDoorn& 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 theMizoram state of India, Chin State in Burma, and the Chittagong Hill Tracts of5 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 theKuki 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 English6 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 STUDYMost research reports on normative nasalance score were made on the basis ofEnglish 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.METHODOLOGYParticipantsNative 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 had15 male native speakers of Mizo language. The mean and standard deviation of the7 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 criteriaAll 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 criteriaAll 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 environmentNasometer 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.INSTRUCTIONSVerbal 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 the8 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 STIMULIFor 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)TESTSThree 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 standardAmerican English sentences (Fletcher, 1978). 9 PROCEDUREThe 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.RESULTSCOMPARISON OF MEAN NASALANCE ACROSS THE PASSAGESMean nasalance for zoo passage, rainbow passage, and nasal sentencesAll 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 2.88DIFFERENCES OF MEAN NASALANCE BETWEEN THE PASSAGESDifferences of mean nasalance between the Zoo Passage and Nasal Sentences, RainbowPassage and Nasal Sentences, Rainbow Passage and Zoo PassageThe 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 ZooPassage 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 NasalSentences, Rainbow Passage and Nasal Sentences, Rainbow Passage and Zoo PassagePassage 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 3.13The Degree of freedom and t-value of comparison of means for Zoo Passage and NasalSentences, Rainbow Passage and Nasal Sentences, Rainbow Passage and Zoo Passage.Table.3: comparison of means for Zoo Passage and Nasal Sentences, Rainbow Passage andNasal 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 <.0001Rainbow Passage Equal 58 39.08 <.0001 and Nasal Sentences Unequal 57.19 39.08 <.0001Rainbow Passage Equal 58 21.30 <.0001 and Zoo Passage Unequal 57.19 21.30 <.000112 Nasalance scores along with Gender DifferencesAll 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 20.33Male 45 38.200 19.09Diff (1-2) 0.422 19.72The degree of freedom and t-value of comparison of means of gender differences.Table.5: Comparison of means of gender differencesVariances Df t-Value Pr>/t/ Equal 88 0.10 0.91Unequal 87.65 0.10 0.9113 Computation of t testFor examining the gender difference of the mean nasalance of the native speakers ofMizo language, t test was computed and the summary of equality of mean nasalance has been reported in Table 6Table.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 PassageEqual variance assumed 2.731 28 .011Equal variance not assumed. 2.731 21.748 .012 Rainbow PassageEqual variance assumed -1.909 28 .067Equal variance not assumed -1.909 27.636 .067Nasal PassageEqual variance assumed 1.007 28 0.322Equal variance not assumed 1.007 27.57 0.32214 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 PASSAGERAINBOW 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 1.71715 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 1.750DISCUSSIONThe 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 KayElemetrics 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 MizoThe 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 readingEnglish 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 SentencesFigure 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 sound17 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 DifferenceThere 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 andMontgomery, 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 and19 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 passagesPaired t-test was done to find out the differences in nasalance score betweenNasal 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 forRainbow Passage as compared to the Zoo Passage as shown in the table 3.CONCLUSIONThe 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 native20 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 PedagogyREFERENCES1. Anderson, R. (1996). Nasometric Values for Normal Spanish-Speaking Females: A Preliminary Report.The Cleft Palate-Craniofacial Journal, 33(4), pp.333-336.2. Britto, A. and Doyle, P. (1990). A Comparison of Habitual and Derived Optimal Voice Fundamental Frequency Values in Normal Young Adult Speakers. J Speech Hear Disord, 55(3), p.476.21 3. Dalston, R., Neiman, G. and Gonzalez-Landa, G. (1993). Nasometric Sensitivity and Specificity: A Cross-Dialect and Cross-Culture Study. The Cleft Palate-Craniofacial Journal, 30(3), pp.285-291.4. Elyan, O. (1988). Sex differences in speech style. Womspeak, 4, pp.4-8.5. Fairbanks, G. (1960). Voice and articulation drill book. New York: Harper & Row.6. Fletcher, S. (1972). Contingencies for Bioelectronic Modification of Nasality. 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Seminar Speech Langage, 4, pp.189-203.13. Kent, R. (1997). The Speech Sciences. San Diego, London: Singular Publishing.14. Lierde, K., Wuyts, F., Bodt, M. and Cauwenberge, P. (2001). Nasometric Values for Normal Nasal Resonance in the Speech of Young Flemish Adults. The Cleft Palate-Craniofacial Journal, 38(2), pp.112-118.15. Litzaw, L. and Dalston, R. (1992). The effect of gender upon nasalance scores among normal adult speakers. Journal of Communication Disorders, 25(1), pp.55-64.16. Mayo, R. and Richardson, A. (1996). Acoustic and perceptual characteristics of the voices of normal adult African-American and White females. Journal of speech, Hearing and Language.17. Mckerns, D. and Bzoch, K. (1970). Variations in velopharyngeal valving: The factor of sex. Cleft Palate Journal, 7, pp.652-662.18. Moll, K. (1962). Velopharyngeal Closure on Vowels. Journal of Speech Language and Hearing Research, 5(1), p.30.19. Oates, J. and Dacakis, G. (1997). Voice changes in transsexuals. Venereology, 10, pp.178-187.20. Prathanee, B., Thanaviratananich, S., Pongjunyakul, A. and Rengpatanakij, K. (2003). Nasalance scores for speech in normal thai children. Scandinavian Journal of Plastic andReconstructive Surgery and Hand Surgery, 37(6), pp.351-355.23 21. Seaver, E., Dalston, R., Leeper, H. and Adams, L. (1991). A study of nasometric values for normal nasal resonance. Journal of speech, Hearing and resonance, 34, pp.715-721.22. Seikel, J. and Drumright, D. (2000). Anatomy and Physiology for speech, language and hearing. 3rd ed. San Diego: Singular Publishing Group, Inc.23. Shprintzen, R., McCall, G., Skolnick, M. and Lencione, R. (1975). Selective movement of the lateral aspects of lateral aspects of the pharyngeal walls during velopharyngeal closure for speech, blowing, and whistling in normal. Cleft Palate Journal, 12, pp.51-58.24. Tachimura, T., Mori, C., Hirata, S. and Wada, T. (2000). Nasalance Score Variation in Normal Adult Japanese Speakers of Mid-West Japanese Dialect. The Cleft Palate-Craniofacial Journal, 37(5), pp.463-467.25. Thompson, A. and Hixon, T. (1979). Nasal airflow during normal speech production. Cleft Palate Journal, 16, pp.412-420.26. Vallino-Napoli, L. and Montgomery, A. (1997). Examination of the Standard Deviation of Mean Nasalance Scores in Subjects with Cleft Palate: Implications for Clinical Use. The Cleft Palate-Craniofacial Journal, 34(6), pp.512-519.27. van Doorn, J. and Purcell, A. (1998). Nasalance Levels in the Speech of Normal Australian Children.The Cleft Palate-Craniofacial Journal, 35(4), pp.287-292.28. Zemlin, W. (1988). Speech & hearing science. Anatomy and physiology. 3rd ed. NewJersy: Englewood Cliffs.24

Influence of Mizo Language on Nasal and Oral Passage in English: a Nasometric Study

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