610 PELL SYSTEM TECHNICAL JOURNAL 



for the particular sound considered; that of MC also in 6 records 

 according to the same test. Speaker FB produced 5 records, and 

 speaker FD, 2 records loo long by the same amount. 



Consider now the general properties of the spoken vowel sound, as 

 deduced from these records. First there is a period of rapid growth in 

 amplitude, lasting about 0.04 second, during which all components are 

 quickl\- produced, and rise nearly to maximum amplitude; second the 

 middle period, the characteristics of which have been noted, lasting 

 about 0.1G5 second, followed by the period of gradual decay lasting 

 about 0.09 second, bringing the total length to appro.ximately 0.295 

 second. There is a tendency to short duration among the "short" 

 vowels (eg. short o, e, i) and a tendency to longer records among the 

 broader sounds, as might be expected. 



The beha\ior of the fundamental frequency (or "cord tone") during 

 the course of the record will follow normal or indi\"i(lual character- 

 istics as has been described. 



The low frequency characteristic appears early, usually before the 

 fourth cycle (for men) or before the se\'enth (for women) and normally 

 is in harmonic relation with the fundamental. In the eleven pure vowel 

 sounds (omitting the ar and er groups) this point was examined at 

 264 locations in 88 records with the result that the harmonic relation 

 obtained in at least 214 cases. On the other hand the normal be- 

 havior of the amplitude of the low frequency characteristic suggests 

 the decay of a transient oscillation during each fundamental cycle — 

 this eflfect being noticeable in at least 64 of the 88 pure vowel records. 

 This transient effect was also noticeable in 13 of the 16 records of ar 

 and er, where the harmonic effect was not so noticeable. The appear- 

 ance of the transient effect depends to some extent on the relative 

 frequencies of the fundamental and the characteristic; where the 

 fundamental period is short, (as often in the case of the women's 

 records) there is not sufficient time for decay of the characteristic tone 

 before it receives a new impetus in the next cycle of the fundamental. 



As noted above, all the records contain high frequency vibrations 

 which are of such amplitude that they suggest characteristic fre- 

 quencies. A general mean of these frequencies would be in the neigh- 

 borhood of 3200 cycles, and in the case of two records b\- speaker FC 

 (Group I and (iroup XIII) the frequency rises to about 5000 cycles. 

 Recalling the usual classification of the vowel sounds into two groups — 

 (1) those of "single" resonance, placed on the left leg of the triangle, 

 (Fig. 12) and (2) those "double" resonance placed on the right leg 

 of the triangle — there are some differences in the behavior of the high 

 frequency components which can be related to these broad classes. 



