The Objective of Research

9 freely, there is no obstruction when it is produced, even it is produced smoothly without any hard effort to produce it. In addition, Murcia, et. al 2009 presented “one of the best ways to appreciate the difference between voiced and unvoiced is to put your hand against your Adam‟s apple i.e. larynx.” 15 Somehow, it is one of the familiar ways to recognize the production of consonants. Here is the terminology of voice and unvoiced. These are to differentiate the consonants sounds when it is produced. “If the vocal folds are held gently together and air under pressure from the lungs is pushed between them, the folds can be made to vibrate evenly to produce the tone we call voiced .” 16 So, when people produce voice sounds, their vocal folds vocal cords in older terminology could be vibrated whilst unvoicedvoiceless not. For example: f vs v. We could feel the difference between them, it could be light when we produce f sound and there is no vibrationunvoiced. On the other side, v is produced by vibration on vocal folds and there is a pressure of the lungs when the air flows. Then, vowel can be classified based on its sounds. According to Kelly 2000, there are two kinds of vowel sounds, single vowel and diphthong that is involving a movement from one vowel sound to another like ei, as in late. Single vowel sounds may be short like i, as in hit or long like i:, as in heat. The symbol : denotes a long sound. 17 It showed that single vowel sound is vowel that appeared one morpheme in a word or when it sounded, which diphthong consists of the combination of two different sounds, and monophthongs are more than two morphemes combined in one sound or they are produced equally. 15 Marianne Celce-Murcia, et. al. Teaching Pronunciation: a Reference for Teachers of English to Speakers of Other Languages, Cambridge: Cambridge University Press, 2009, P.42 16 Michael Arshby and John Maidment, Introducing Phonetic Science, Cambridge: Cambridge University Press, 2005, pp.22-23 17 Gerald Kelly, How to Teach Pronunciation, England: Pearson Education Limited, 2000, Series Editor: Jeremy Harmer, p.84