Cardinal Vowels

Therefore, a vowel description will usually be based on auditory judgments of sound relationships, together with some articulatory information, especially as regards the position of the lips. (Cruttenden 2001:34)
Cardinal Vowels
Difficulty of Describing Vowels
Three factors for the description of vowels: The position of the soft palate:raised for oral vowels, lowered for nasalized vowels. The kind of aperture formed by the lips:degrees of spreading or rounding. The part of tongue which is raised and the degrees of raising.
The End
Thank you
The Cardinal Vowel Diagram
C.1 [i] C.2 [e] C.3 [ε ] C.4 [a] C.8 [u]
C.7 [o]
O
C.6 [ ] C.5 [ɑ]



From this diagram, the front, center, and back of the tongue are distinguished, as are four levels of tongue height: The highest position the tongue can achieve without producing audible friction; The lowest position the tongue can achieve; Two intermediate levels,dividing the intervening space into auditorily equivalent areas.
The Cardinal Vowel Diagram
C.1 [i] C.2 [e] C.3 [ε ] C.4 [a] C.8 [u]
C.7 [o]
O
C.6 [ ] C.5ቤተ መጻሕፍቲ ባይዱ[ɑ]
The eight cardinal vowels are numbered as CV1[i], CV2[e], CV3[ε ], CV4[a], CV5[ɑ], CV6[ ], CV7[o], and CV8[u]. The first five are unrounded, while the other three are rounded. Textbook p.200
The Cardinal Vowel Diagram

The cardinal vowel diagram is a set of standard reference points based on a combination of articulatory and auditory judgments.

References
Cruttenden, A. 2001. Gimson’s Pronunciation of English. 6th ed. London: Edward Arnold. Roach, P. 1991. English Phonetics and Phonology: A Practical Course. 2nd ed. Cambridge University Press. 戴炜栋，1989，《简明英语语言学教程》，上海： 上海外语教育出版社。 何善芬, 1992, 《实用英语语音学》,北京:北京 师范大学出版社。 胡壮麟，2001，《语言学教程》﹙修订版﹚，北 京：北京大学出版社。
Cardinal Vowels

According to Daniel Jones, the cardinal vowels are a set of vowel qualities arbitrarily defined, fixed and unchanging,intended to provide a frame of reference for the description of the actual vowels of existing languages.