62 PKOCEEDINGS OF THE AMERICAN ACADEMY. 



Both cases cited above are only broadly illustrative. As a matter 

 of fact the effect of the room aud the effect of the audience in the 

 room is perceptibly different at the two ends of the register of the violin 

 and of the double-bass viol. 



There is still a third effect, which must be considered to appreciate 

 fully the practical significance of the results that are being presented. 

 This is the effect on the quality of a sustained tone. Every musical 

 tone is composed of a great number of partial tones, the predominating 

 one being taken as the fundamental, and its pitch as the pitch of the 

 sound. The other partial tones are regarded as giving quality or color 

 to the fundamental. The musical quality of a tone depends on the 

 relative intensities of the overtones. It has been customary, at least 

 on the part of physicists, to regard the relative intensities of the 

 overtones, which define the quality of the sound, as depending simply 

 on the source from which the sound originates. Of course, primarily, 

 this is true. Nevertheless, while the source defines the relative in- 

 tensities of the issuing sounds, their actual intensities in the room 

 depend not merely on that, but also, and to a surprising degree, on 

 the room itself. Thus, for example, given an eight-foot organ pipe, if 

 blown in an empty room, such as that described above, the overtones 

 would be pronounced. If exactly the same pipe be blown with the 

 same wind pressure in a room in which the seats have been covered 

 with the elastic felt, the first upper partial will bear to the funda- 

 mental a ratio of intensity diminished over 40 per cent, the second 

 upper partial a ratio to the fundamental diminished in the same per 

 cent, the third upper partial a ratio diminished over 50 per cent, 

 while the fourth upper partial will bear a ratio of intensity to the 

 fundamental diminished about 60 per cent. Quality expressed numer- 

 ically in this way probably does not convey a very vivid impression 

 as to its real effect. It may signify more to say merely that the 

 change in quality is very pronounced and noticeable, even to com- 

 paratively untrained ears. On the other hand, if one were to try the 

 experiment with a six-inch instead of with an eight-foot organ pipe, 

 the effect of bringing the elastic felt cushions into the room would 

 be to increase the relative intensities of the overtones, and thus to 

 diminish the purity of the tone. 



All tones below that of a six-inch organ pipe will be purified by 

 bringing into the room elastic felt. All tones above and including that 

 pitch will be rendered less pure. The effect of an audience coming 

 into a room is still different. Assuming that the audience has filled 

 the room and so covered all the elastic felt cushions, the effect of the 

 audience is to purify all tones up to violin C4 512, and to have very 



