CHAPTER XIV 



THE EAR. HEARING AND EQUILIBRATION. TASTE AND 



SMELL 



Functions of the Ear. The ear is not solely an organ of hearing. 

 It includes, in addition, the highly important structures by which 

 is mediated the sense of equilibrium. Hearing is, however, its 

 familiar function, and we will consider it first in order. To be able 

 to discuss intelligently the apparatus for hearing we must have in 

 mind the fundamental facts about the agency by which the sense 

 is aroused, namely, sound. 



The Loudness, Pitch, and Timbre of Sounds. Sounds, as sensa- 

 tions, fall into two groups notes and noises. Physically, sounds 

 consist of vibrations, and these, under most circumstances, when 

 they first reach our auditory organs, are alternating rarefactions 

 and condensations of the air, or aerial waves. When the waves fol- 

 low one another uniformly, or periodically, the resulting sensation 

 (if any) is a note; when the vibrations are irregular it is a noise. 

 In notes we recognize (1) loudness or intensity; (2) pitch; (3) qual- 

 ity or timbre, or, as it has been called, tone color; a note of a given 

 loudness and pitch produced by a flute and by a violin has a dif- 

 ferent character or individuality in each case; this quality is its 

 timbre. Before understanding the working of the auditory mech- 

 anism we must get some idea of the physical qualities in ob- 

 jective sound of which the subjective differences of auditory 

 sensations are signs. 



The loudness of a sound depends on the force of the aerial waves; 

 the greater the intensity of the alternating condensations, and rare- 

 factions of these, the louder the sound. The pitch of a note depends 

 on the length of the waves, that is, the distance from one point of 

 greatest condensation to the next, or (what amounts to the same 

 thing) on the number of waves reaching the ear in given time, say 

 a second. The shorter the waves the more rapidly they follow 

 one another, and the higher the pitch of the note. When audible 



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