VOICE. 



14-79 



and S their specific gravity ; then p will be 

 equal to able, and equation (1.) becomes 



i=2l 



- - - (2.) 



and the number of such vibrations in I" will be 

 N= ^jg - - - (3 ) 



We observe, in the first place, that if all 

 other things remain the same, the number of 

 vibrations varies inversely as the length of 

 the cord ; hence, if the vocal ligaments were 

 divided by nodes into n ventral segments, 

 each segment might be considered a separate 

 vibrating ligament, whose length would be 

 7;tli of the vocal cord, and consequently the 

 number of its vibrations in a given time would 

 be n times as many as that ot the whole cord. 



Owing to the elasticity of the thyro-aryte- 

 noid ligaments, their lengths, when in a state 

 of repose, differ considerably from those which 

 they present under the greatest tension. They 



differ also in the two sexes. In a series of 

 experiments by Miiller, the differences of 

 length were observed to be as represented in 

 the following table, the figures of which are 

 in inches and decimals of an inch. From these 

 experiments it appears that the lengths of the 

 male and female vocal cords in repose are 

 nearly as 7 to 5, and in tension as 3 to 2. In 

 boys at the age of fourteen, the length is to 

 that of females after puberty as 6'25 to 7, so 

 that the pitch of the voice is nearly the same. 

 These experiments afford an idea, although an 

 imperfect one, of the elasticity of the vocal 

 ligaments. It has always been a subject of 

 surprise, if the thyro-arytenoid ligaments obey 

 the laws of strings, how such short and narrow 

 laminae should produce such very grave tones 

 as many bass singers are capable of uttering ; 

 and this struck M. Biot as one of the circum- 

 stances which in his opinion prove their mode 

 of vibration to be unlike that of strings. He 

 asks, " Ou pourroit-on trouver la place ne- 

 cessaire pour donner a cette corde la longueur 

 qu'exigent les sons les plus graves ?" 



The author is acquainted with some bass 

 singers who can produce the note C which 

 results from sixty -four musical vibrations. 

 Let us now investigate this phenomenon more 

 closely, and endeavour to explain how such 

 grave "tones are produced by such extremely 

 short membranes. Miiller has contrived 

 several ingenious pieces of mechanism, seen in 

 fgs. 891, 892, and S93, by means of which 

 he was enabled to estimate the amount of 

 tension, lateral compression, and atmospheric 

 pressure on the vocal cords, during the pro- 

 duction of sound. In order to find the 

 variations in the amount of condensation of 

 air in the vocal organs in the production of 

 sounds differing in pitch and intensity, the 

 apparatus was furnished with a manometer 

 (Jig. 893, v}. From that portion of the ex- 

 periment which was confined to the investiga- 

 tion of the effects produced by tension of the 



vocal, compared with that of musical cords, 

 he obtained results which are recorded in the 

 following table. 



* A loth =225-5531 grs. English. 

 5 B 4r 



