chap, xxxn.] MUSICAL SOUND. 423 



are conducted to the tympanum. The concavities of 

 the concha and of the inner surface of the tragus are 

 adapted specially for directing the sonorous waves 

 into the external canal. The two surfaces are so 

 arranged with regard to one another that sound waves 

 coming from before will be reflected by the concha on 

 to the inner face of the tragus, where they undergo a 

 second reflection, which concentrates them in the 

 direction of the external canal. 



CHAPTER XXXII. 



MUSICAL SOUND. 



ALL sounds are due to vibrations, but the differ- 

 ence between ordinary sounds (between noises, for in- 

 stance) and musical sounds is in the rhythmic or 

 periodic character of the latter. Musical sounds are 

 also distinguished by their continuous character, the 

 vibrations following one another with such rapidity 

 that each one is not perceived separately, the per- 

 ception being only of the fused whole. Various 

 characters of musical sounds must be noted, namely, 

 their loudness or intensity, their pitch, and their 

 quality. 



The intensity of any sound is due to the 

 amplitude of the vibration, the extent of the excursion, 

 as one might say, the height of the wave. 



The pitch of a musical sound is determined by 

 the rapidity of the vibrations, the number of 

 vibrations affecting the auditory apparatus in a second 

 of time. This has been shown in various ways. 

 Savart, for instance, used a toothed wheel which could 

 be revolved with varying degrees of rapidity. As the 



