A record for "Mitchell" is shown in Fig. 2. It begins with very faint vibrations for "m"; thereupon follow strong vibrations for the vowel "i." The straight line after the vowel indicates a complete stoppage of breath, that is, the sound is an occlusive. After the occlusion the line rises at first gently and then strongly, as the result of the stoppage being ended and the air rushing out rapidly; this phenomenon is called an explosion. The sound at this point is therefore an occlusive with an explosion. This is the sound "ch" which is indicated by the spelling "tch" in the word recorded. The word ends with strong vibrations for the vowel "e" and fainter ones for "l."
A record of the word "nut" by the same speaker is shown in Fig. 3. It begins with very faint vibrations for "n" followed by stronger ones for "u." The straight line indicates the occlusion for the "t." The strong sharp rise of the line indicates that the "t" ends with a sharp explosion. This explosion is quite different from the more gradual explosion of "ch" as shown in Fig. 2.
A record of the word "nutshell" by the same speaker is shown in Fig. 4. Very faint vibrations for "n" are followed by stronger ones for "u." The straight line indicating the occlusion of the "t" is followed by a very gradually rising line which remains for a time at quite a distance above the base line. This indicates that the occlusion of the "t" was not followed by an explosion, but by a continuous rush of air. This portion of the record is typical of the records for "sh."
A record of final "ch" in the word "atch" is shown in Fig. 5, a record of initial "ch" in "chew" in Fig. 6. Records of "j" differ from those of "ch" in showing small vibrations during the occlusion and the explosion. These are due to the vibrations of the larynx which are present during "j" and not during "ch." The "j" is said to be "sonant," the "ch" to be "surd."
These records and many others from the same person and from other persons (Americans) show clearly that the sounds "ch" and "j" consist of an occlusion with an explosion following it, that the explosion is more gradual than the explosion for "t" and "d," and that the explosion is of quite a different character from the rush of air during "sh." The conclusion is unavoidable that "ch" and "j" are not compound sounds, but simple occlusives with characteristic explosions.
By coating the tongue with ultramarine just before speaking, "ch" or "j" or by any of the other methods of palatography a record of the contact of the tongue with the palate may be obtained. The regions of contact for "ch" and "j" are found to be larger than those for "t" and "d."
The final conclusion is that "ch" (c) and "j" (j) are to be recognized as individual sounds quite distinct from the compound sounds "tsh" and "dsh."
- Scripture, "Elements of Experimental Phonetics," chapter XXI.