An Experimental Study On The Pronunciation Defects Of Mandarin Single-character Sounds After Children's Cleft Palate Surgery

Cleft lip and palate is the most common congenital malformations in human oral and maxillofacial regions.Cleft palate repair surgery will provide a physiological basis for patients with cleft palate to make clear and understandable speech.But there are still some patients with various speech disorders due to incomplete palatopharyngeal closure or poor pronunciation habits,that is,cleft palate speech.This article examines the pronunciation of vowels,compound vowels,voiceless consonants,approximant and nasal ends in monosyllabic sounds in patients with the velopharyngeal competency group and the velopharyngeal insufficiency group after cleft palate operation from three aspects: perception,acoustics and nasalization.Compared with the performance of normal children,the results are as follows:1.Types of cleft palate children’s vowel errors include hypernasality,substitution,complex vowelization,addition,tongue offset,unrounded lip,and labiodental /u/,etc.The nasalization of the seven vowels from small to large is control group,VPC group,VPI group,so nasalization can be used as an important parameter to measure the degree of hypernasality,for non-nasal sounds.Nasalization is above 0-40,40-60,60-80,80 or more,the levels of hypernasality can be classified as normal,mild,moderate and severe(Xiujuan Shi 2019).The hypernasality of vowels /i y/ in the VPC group are mild,others are normal.Thehypernasality of vowel /a/ in the VPI group is normal,/? ?/ is mild,/u y ?/ is moderate,/i/ is severe.Among the seven vowels,vowel /i/ can be used as a sensitive indicator for detecting cleft palate sounds and should not be used as vowel /a/.2.Types of compound vowel errors in children with cleft palate include addition,deletion,simplify,substitution and nasalization,etc.The difference between the cleft palate children and the control group is mainly reflected in F2.Both the VPC group and the VPI group have difficulty in mastering the movement of compound vowels,which is mainly shown in /ei、i?、y?、iau、iou、uai、uei/.The unrounded lip is mainly reflected in /ou/ and /ua/.The nasalization of compound vowels from small to large is control group,VPC group,VPI group.The hypernasality of the /i/ in /i?、iau、iou/ and the /y/ in /y?/ in VPC group are mild,others are normal.The hypernasality of /a/ in /ai、au、ua、iau、uai/ and the /o/ in /uo、ou、iou/ are normal,the /i/ in /i?、iou/ and the /y/ in /y?/ is moderate,others are mild.3.The types of voiceless consonant errors in children with cleft palate include deletion,substitution,voiced sound,nasal air emission and mixed pronunciation,among which substitution and deletion are the main ones.The substitution of consonant is mainly concentrated in lingua-alveolar and the deletion of consonant is mainly concentrated in lingua-velar.The stops and fricative of the VPC and VPI groups are better than affricate,the aspirated sounds are better than those of unaspirated sounds,and the bilabial sounds,retroflex and lingua-velar are better than the lingual-palatal consonants,dental consonants and alveolar consonants.The VOT of the stops and the frictive time of the fricative /s ? ?/ in the control group,the VPC group and the VPI group show a stepwise increase.The DOF of the six affricates are the largest in the VPI group.The phonemes of cleft palate group and control group are mainly concentrated on the unaspirated.In terms of gender,VOT,DOF,and frictive time of female children with cleft palate is longer than that of males,which is related to the physiological structure,anatomical differences,and social phonetic factors of male and female.The sequence of correction of voiceless consonants in cleft palate is: bilabial,labiodental,retroflex,lingua-velar,lingual-palatal,alveolar,dental;stop,fricative,affricate;aspirated,unaspirated.4.In children with cleft palate,the types of approximant errors include hypernasality/hyponasality,substitution,deletion,retroflection or nasal air emission,etc.The nasalization of /m n/ from large to small is control group,VPC group,VPI group.Nasalization can be used as an important parameter to measure the degree of hyponasality.For nasal sounds,nasalization is above 80 or more,60-80,40-60,0-40,respectively,and the level of hyponasality can be set as normal,mild,moderate,and severe(Xiujuan Shi 2018).The sounds /m n/ in the VPC group and the VPI group are no hyponasality.The nasalization of /l ?/ from small to large is control group,VPC group,VPI group.The hypernasality in the VPC group is mild,and the VPI group is moderate.The boundary between the VPC group and the VPI group is unclear,especially the VPI group.The order ofcorrection of approximant is /m n l ?/.5.Types of nasal ends errors in children with cleft palate include substitution,deletion,nasalization,weakening,addition and nasalization,etc.The nasal end /-?/ has better pronunciation than /-n/,/-?/ is relatively stable,and/-n/ is easier to fall off.Nasalization can also be used as an important parameter to measure abnormal nasal ends.For nasal ends,nasalization above 60 is considered normal.Nasalization between 40 and 60 is considered mild.Nasalization is below 40 and the complete deletion of the nasal ends is considered to be a severe abnormality(Xiujuan Shi,Tong Xia 2019).The nasalization of the control group and the VPC group from large to small is /-?/,/-n/,while the VPI group is /-n/,/-?/.The physiological obstacles in the VPI group still exist,and surgical treatment is urgently needed.The physiological structure of the VPC group has been restored,and speech training can be carried out.In this experiment,a vocabulary of evaluation of cleft palate(both Yinping tone)is established based on sensitive phonemes,which reflects the phoneme combination and opposition of Chinese as much as possible.In addition,the type of cleft palate before surgery has little effect on the speech.The speech defects of adults with cleft palate and children with cleft palate were basically the same.