CHAPTER X 



PHYSIOLOGICAL ACOUSTICS 



91. Analysis of Sound Sensations. Musical Notes. 



The vibrations of elastic bodies and the propagation of 

 waves through the atmosphere are subject to well-ascertained 

 mechanical laws, and the inferences drawn from these can be 

 controlled by more or less decisive experiments. But when 

 we approach the field where the human mechanism comes into 

 play, we are met by the peculiar difficulties which are inherent 

 in the observation and study of subjective phenomena. In 

 particular, when we endeavour to analyse a familiar complex 

 sensation into its elements, we are attempting a task for which 

 the experience of daily life has peculiarly unfitted us. Thus 

 we may have been accustomed to interpret the sensation in 

 question as indicating the presence of a particular object, or 

 the occurrence of a particular kind of event, in a particular 

 place. The elements of which it is made up give individually 

 little or no information; it is the combination which is significant, 

 and attention to the details would only distract from what is of 

 immediate practical interest. To use a rough and indeed an 

 utterly inadequate illustration, it is as if we were to insist upon 

 spelling every word we read. 



The theory of sense-perception, especially in relation to 

 optics and acoustics, is a fascinating subject, but it cannot be 

 dealt with here. The student who is unversed in it may be 

 referred to the writings of Helmholtz*. 



* The theory is explained in its acoustical bearings in the Tonempfindungen, 

 already cited (p. 3). It is also discussed from the optical point of view in his 

 Handbuch der physiologischen Optik, 2nd ed., Hamburg and Leipzig, 1896. 

 Elementary expositions will be found in the two volumes of his Vortrage und 

 Reden, Brunswick, 1884, of which there is an English translation by E. Atkinson, 

 with the title: Popular Lectures on Scientific Subjects, 2nd ed., London, 1893. 



