Ans. The cardinal vowels system was developed by English phonetician Daniel Jones. The system is intended as a system of reference for the unambiguous classification of vowel values in a language. Cardinal vowels are mainly vowel possibilities. All sounds are peripheral. In other words, cardinal vowels are a set of fixed standard reference points used by phoneticians in describing the sounds of other languages.
Cardinal vowels are not vowels of any particular language; but a measuring system. Since no two speakers speak alike, there is always a difference in the pronunciation. Vowels are produced with any obstruction in the oral cavity. This makes the tasks of identification and classification of vowels difficult. Realising the problem, Daniel Jones suggested the notion of cardinal vowels which will serve as reference point in the description and classification of vowels. According to him, a cardinal vowel is produced when the tongue is in an extreme position, either front or back, high or low. Therefore, cardinal vowels are a set of vowel sounds having known acoustic qualities and known tongue and lip positions.
However, a set of eight cardinal vowels forms a convenient basis for describing the vowels of any language. They are represented in the International Phonetic Alphabet (IPA) as follows:
Figure : Diagram of cardinal vowels.