DEFINITION
In phonetics, a diphthong is a gliding monosyllabic speech sound that starts at or near the articulatory position for one vowel and moves to or toward the position of another.PARAMETERS FOR DEFINING DIPHTHONGS
Diphthongs present greater difficulty to people learning English because during the articulation of such vowels the tongue travels between two fixed locations. It is important to know exactly what to do with the speech organs, (•the position of the tongue • lip-shape and tension •size of mouth opening) in each location and the manner and direction of the movement.Vowel sounds are more difficult to define in articulatory terms than consonants and the number of vowels that can be produced by human speech organs is fairly great. Therefore, to help identify vowels in different languages, phoneticians use a series of reference vowels, called cardinal vowels with which to compare them. The Cardinal Vowel System was designed by the phonetician Daniel Jones as a means of establishing fixed reference points for the phonetic description of vowel quality. It has become customary to locate cardinal vowels in a four-sided figure as illustrated below:
Having established the cardinal vowel diagram as a basic system of reference we can now proceed to a brief description of diphthongs of English and of their distribution in a manner similar to that used in the case of consonants.
THE DESCRIPTION AND DISTRIBUTION OF DIPHTHONGS
There are eight English diphthongs altogether. It is useful to distinguish them between centring and closing diphthongs:A. The first three diphthongs are centring diphthongs. They have the neutral "shwa" vowel sound /ə/, which occurs in grunting noises and the weak forms of "the" and "a", as the finishing position.
/ɪə / ইয়া : This diphthong starts with a front unrounded vowel situated between cardinal vowels 1 [i] and 2 [e] and then moves towards the central unrounded vowel / ə / between half-close and half-open position. The diphthong is distributed in all three basic positions:
/eə/ এয়া : This diphthong starts with the front unrounded vowel / e / and then moves towards and then moves towards the central unrounded vowel / ə / between half-close and half-open position. The diphthong is distributed in all three basic positions:
/ʊə/ উয়া : This diphthong starts with the back rounded vowel / ʊ / and then moves towards the back rounded vowel / ʊ / between close and then moves towards the central unrounded vowel / ə / between half-close and half-open position. This diphthong is distributed only in medial and final positions:
B. The next three diphthongs are closing diphthongs. They have the vowel sound /ɪ/ in "pit" or "if" as the finishing position.
/eɪ/ এই : It starts with a front unrounded vowel situated between cardinal vowels 2 [e] and 3 [ε]and then glides to a front-close vowel / ɪ / in-between cardinal vowels 1 [i] and 2 [e]. The diphthong is distributed in all three basic positions:
/aɪ/ আই : It is the diphthong that actually implies the amplest articulatory movement of the speech organs that starts from the position of an open vowel between front and back (similar to ʌ in cut) and then glides towards / i /. The diphthong is distributed in all three basic positions:
/ɔɪ/ অই : This diphthong starts from a half-open back vowel, situated between cardinal vowels 6 [ɔ] and 7 [o] and ends in a front-close vowel / ɪ /, somewhere in the vicinity of cardinal vowel 1 [i]. Like the preceding diphthong, it also involves an ample articulatory movement from a back vowel to the front part of the imaginary vowel chart. It is distributed in all three basic positions:
C. The last two diphthongs are also closing diphthongs. They have the back rounded vowel / ʊ / as the finishing position.
/əʊ/ ওউ : This diphthong starts with the central unrounded vowel / ə / and then moves towards the back rounded vowel / ʊ/ between close and half-close position. It is distributed in all three basic positions: old, gold, flow:
/aʊ/ আউ : This diphthong starts with an open back rounded vowel (similar to ɑ: ) and then moves towards the rounded vowel /ʊ/ between close and half-close position. It is distributed in all three basic positions: ouch, loud, bough:
THE DIFFERENCE BETWEEN DPHTHONGS AND LONG VOWELS
Diphthongs and long vowels differ from each other in a number of ways. We can differentiate them in the following manner:- The basic difference between diphthongs and long vowels is that whereas the former is a gliding vowel, the later is a pure vowel. During the articulation of long vowels, the tongue stays at one fixed location in the mouth. But in the case of diphthongs, the tongue is not stationary; rather it moves one position to another.
- Diphthongs and long vowels can be distinguished from one another with regard to phonetic representation. Though diphthongs are single speech sounds, they are usually represented, in phonetic transcription of speech, by means of a pair of characters indicating the initial and final configurations of the vocal tract.
- Long vowels are independent. But diphthongs are dependent because they do not have any individual starting points, they always start either from a short or long vowel or vowels with similar qualities.
- Lastly, we can distinguish diphthongs from long vowels in relation to quantity. Whereas diphthongs are eight in number, the long vowels are only five in number.
BANGLA DIPHTHONGS
Bengali language is renowned for its wide varieties of diphthongs or vowel combinations. But the parameters we generally use to produce these diphthongs are quite different than those of English ones. Majority of Bengali diphthongs posses different starting and ending points. As a result, all of these combinations cannot be compared to English diphthongs. Therefore, in Bengali, we have only two diphthongs- /ঐ/ and /ঔ/, which are very much similar to the English- /ɔɪ/and /əʊ/.
/ ঔ / : This diphthong starts from a half-open back vowel, situated between cardinal vowels 6 [ɔ] and 7 [o] and moves towards close and half-close position, somewhere in the zone of cardinal vowel 1 [i]. For example: বউ [wife], নৌকা [boat]
/ ঐ / : The starting point for this diphthong is central position between half-close and half-open position. Then there is a glide towards close and half-close position, somewhere in the area of cardinal vowel 8 [u]. For instance: কই [where], নৈতিক [moral]
References
“Diphthongs.” Encyclopædia Britannica. 2008. Encyclopædia Britannica Inc. 29 March 2008
<http://www.britannica.com/EBchecked/topic/164541/diphthong>.
“English Diphthongs.” Pétur Knútsson. 2008. Pétur Knútsson. 29 March 2008
<https://notendur.hi.is/peturk/index.html>.
“English Diphthongs.” Ted Power. 2008. Ted Power. 29 March 2008
<http://www.btinternet.com/~ted.power/esl0105.html>.
Varshney, Dr. R.L. An Introduction of Linguistics & Phonetics. Dhaka: BOC, n.d.
