VOICE IN MAN AND IN ANIMALS. 



393 



by their timbre ; we hear some one speaking, and recognize who it 

 is without seeing him ; or we hear a strain of music, with several 

 sounds of the same pitch, but we readily by the timbre distinguish 

 from one another the violin, the flute, the clarionet. The differences 

 are the result of the different forms of the vibrations ; this may be 

 demonstrated by experiment. Whether we consider the movements 

 of a pendulum or of a tuning-fork, in every case the vibration, when 

 traced automatically, gives a characteristic line for each variety of 

 timbre. If by means of the ear, rendered highly sensitive by long 

 practice, we study to distinguish the different forms of the waves, we 

 recognize in addition to the fundamental sound other higher sounds, 

 the harmonics. Helmholtz's resonators aid the analysis by the ear. 

 The resonator is a little hollow sphere with two open tubes, one of 

 them conical, so as to fit into the auditory passage. The fundament- 

 al sound, which is much deeper than the other sounds, is thus con- 

 siderably reenforced. In like manner, with the aid of proper resona- 

 tors, it is easy to hear the harmonics of the human voice. Helm- 

 holtz ascribes the diversity of timbres to the intensity of the har- 

 monics. Physiologists hold that there exist other causes, as yet not 

 ascertainable. 



In the state of rest, when respiration is performed without effort 

 and with regularity, the vocal cords are almost motionless ; during 

 the alternations of inspiration and expiration, the orifice of the glot- 

 tis does not alter its form. After a cry has been uttered, there occurs 

 a deep inspiration, and then the vocal cords diverge, widening the 

 aperture. When expiration is suspended or performed slowly, the 

 orifice closes more or less. At the moment of emitting a sound, the 

 lateral cartilages of the larynx are brought near to one another, and 

 the vocal cords are suddenly made tense and applied closely to each 

 other in their anterior portion, or even throughout their entire 

 length ; the passage of air is thus intercepted. Instantly the orifice 

 opens again, and the air in passing between the vibrating vocal 

 cords is itself thrown into vibrations, and sound is the result. These 

 operations are performed gently or forcibly according to circum- 

 stances. Here we have the " glottic sound," as it is called by Mandl ; 

 isolated, it is inaudible, but it reaches our ear only after it has 

 traversed the pharynx and the mouth ; the vibrations of the air modi- 

 fy it. Every one has remarked the change produced in sounds by 

 their passing through a tube or the like ; for instance, when we hear 

 a voice coming from the bottom of a well. Hence the voice is formed 

 by the combination of the sounds of the glottis and of the cavities 

 lying above the larynx : when these cavities are passive, the voice 

 is inarticulate; when they undergo certain changes of form, the voice 

 becomes articulate. 



The pharynx and the mouth, which serve as a resonating box, pro- 

 duce sounds whenever the air they contain is made to vibrate by the 



