some extent, ye the position of the second vowel is often not reached. They first element of an English diphthong is strong, clear and distinct. The second element is rather weak and unclear 1) The closing diphthongs(合口双元音) As the sound is made the tongue moves from an opener position to a closer position and the opening between the jaws is rather wide at the beginning and then becomes narrow as the glide progresses, /ei/ there is a slight closing movement of the lower jaw /ai/ the glide is smooth and loudness becomes less as it progresses /ou/ the glide may start with /u/. the tongue position for it is a little higher and closer tan for/ /au/ start with/a/ and then glides away to/u/ with the lips getting slightlyrounded /ia/ glides from /i/to /e/. The lips are spread throughout The centring diphthongs(集合双元音 Feature: Those three: the lips are spread throughout Chapter 4 classification of consonants Rules I)The work of the vocal cords 2) Place of articulation 3)Manner of articulation The difference between the voiced and voiceless consonants is mainly one of strength. The voiceless consonants are usually aspirated strong and long, the voiced consonants are usually unaspirated weak and short Place of articulation 1. the obstruction is formed by the two lips, e. g /b//p//m//w/ 2. the obstruction is formed between the lower lip and the upper teeth, e.g. /f//v 3. the obstruction is formed between the tip of the tongue and the upper front teeth E. g /6//07 4. the obstruction is formed between the blade of the tongue and the teeth-ridge, e.g /t//d//s//z//ts//dz//n/// 5. the obstruction is formed between the tip of the tongue and the back of the teeth-ridge, e. g /r//tr//dr 6. the obstruction is formed when the blade of the tongue is raised towards the teeth-ridge and the front of the tongue towards the hard palate, e. g /tf//d3//5/, /3/ 7. the obstruction is formed between the front of the tongue and the hard palate, e.g 8. the obstruction is formed between the back of the tongue and the soft palate, e.g 9. the obstruction is formed in the glottis, between the two vocal cordssome extent, ye the position of the second vowel is often not reached. They first element of an English diphthong is strong, clear and distinct. The second element is rather weak and unclear. 1) The closing diphthongs(合口双元音) As the sound is made the tongue moves from an opener position to a closer position and the opening between the jaws is rather wide at the beginning and then becomes narrow as the glide progresses, /ei/ there is a slight closing movement of the lower jaw. /ai/ the glide is smooth and loudness becomes less as it progresses. /əu/ the glide may start with /əu/. the tongue position for it is a little higher and closer tan for /ɔ:/ /au/ start with /a/ and then glides away to /u/ with the lips getting slightlyrounded. /iə/ glides from /i/ to /ə/ . The lips are spread throughout. The centring diphthongs （集合双元音） Feature: Those three : the lips are spread throughout. Chapter 4 classification of consonants Rules : 1)The work of the vocal cords. 2) Place of articulation. 3) Manner of articulation. The difference between the voiced and voiceless consonants is mainly one of strength. The voiceless consonants are usually aspirated, strong and long, the voiced consonants are usually unaspirated weak and short. Place of articulation. 1. the obstruction is formed by the two lips, e.g./b/ /p/ /m/ /w/ 2. the obstruction is formed between the lower lip and the upper teeth, e.g./f/ /v/ 3. the obstruction is formed between the tip of the tongue and the upper front teeth. E.g. /Θ/ /ð/ 4. the obstruction is formed between the blade of the tongue and the teeth-ridge, e.g. /t/ /d/ /s/ /z/ /ts/ /dz/ /n/ /l/ 5. the obstruction is formed between the tip of the tongue and the back of the teeth-ridge ,e.g ./r/ /tr/ /dr/ 6. the obstruction is formed when the blade of the tongue is raised towards the teeth-ridge and the front of the tongue towards the hard palate,e.g. /tʃ/ /d3/ /ʃ/, /ʒ/ 7. the obstruction is formed between the front of the tongue and the hard palate, e.g. /j/ 8. the obstruction is formed between the back of the tongue and the soft palate, e.g. /k/ /g/ / ŋ/ 9. the obstruction is formed in the glottis, between the two vocal cords