Page:An outline of English phonetics ... with 131 illustrations (IA cu31924027389505).pdf/34

16 opening E at the end of the rod, a musical sound of definite pitch is produced by the reed. The quality (timbre) of this sound depends on the length of the part of the cylinder projecting beyond the piston, and by varying the position of the piston a large number of distinct qualities of tone are obtainable, some of the sounds having considerable resemblance to some of the well known vowels.

71. The shape of the air passage above the larynx is governed, and hence vowel quality is governed, chiefly by the position of the main part of the tongue (though also to a large extent by the position of the lips, § 88). It is therefore convenient to classify vowels according to the position of the main part of the tongue. (Note that the position of the tip of the tongue has no great effect on vowel quality, except in the cases noted in Chapter XVI, which do not occur in normal English.)

72. A point which cannot fail to strike anyone comparing the qualities (timbres) of various vowels is that some vowels (e. g. the vowels in see, calm) have clear and well-defined quality, while others (e.g. the vowel in bird) have a more obscure sound.

73. The vowels of obscure quality are chiefly those in which the tongue is in an intermediate vowel position, not raised markedly at the back or in the front, and not too low down in the mouth. The vowels of well-defined quality are chiefly those in which the tongue is remote from such an intermediate position, that is to say those in which the tongue is markedly raised in the front or at the back or is quite low down in the mouth.

74. The chief vowels of well-defined quality may be conveniently classed in five groups, known as vowels of the i type, vowels of the e type, vowels of the ɑ type, vowels of the o type and vowels of the u type.

75. If we examine the tongue positions of the typical sounds of these five classes we find that the highest points of the tongue lie roughly on the sides of a triangle as shown in figs. 9 and 10. This triangle is known as the “Vowel Triangle”.

76. Vowels which have the highest point of the tongue approximately on the left-hand side of this triangle, i.e. which are intermediate between the sounds of the a type and sounds of the i type are called. Such are the vowels in it, get. Those in which the highest point of the tongue is approximately on the right-hand side of the triangle, i. e. which are intermediate between sounds of the a type and sounds of the ɑ type, are called. Such are the vowels in put, saw.