SABINE. — AKCHITECTURAL ACOUSTICS. 63 



little effect on all tones from that pitch upward. On very low tones 

 the effect of the audience in the room is more pronounced. For 

 example, again take Ci G4, the eft'ect of the audience will be to 

 diminish its first overtone about sixty per cent relative to the funda- 

 mental and its second overtone over seventy -five per cent. 



The effect of the material used in the construction of a room, and 

 the contained furniture, in altering the relative intensities of the fun- 

 damental and the overtones, is to improve or injure its quality accord- 

 ing to circumstances. It may be, of course, that the tone desired is a 

 very pure one, or it may be that what is wanted is a tone with pro- 

 nounced upper partials. Take, for example, the "night horn " stop in 

 a pipe organ. This is intended to have a very pure tone. The room 

 in contributing to its purity would improve its quality. On the other 

 hand, the mixture stop in a pipe organ is intended to have very pro- 

 nounced overtones. In fact to this end not one but several pipes are 

 sounded at once. The effect of the above room to emphasize the fun- 

 damental and to wipe out the overtones would be in opposition to the 

 original design of the stop. To determine what balance is desirable 

 must lie of course with the musicians. The only object of the present 

 series of papers is to point out the fundamental facts, and that our 

 conditions may be varied in order to attain any desired end. One 

 great thing needed is that the judgment of the musical authorities 

 should be gathered in an available form ; but that is another problem, 

 and the above bare outline is intended only to indicate the importance, 

 of extending the work to the whole range of the musical scale, — the 

 work undertaken in the present paper. 



The method pursued in these experiments is not very unlike that 

 followed in the previous experiments with C4512. It differs in minor 

 detail, but to explain these details would involve a great deal of 

 repetition which the modifications in the method are not of sufficient 

 importance to justify. 



Broadly, the procedure consists first in the determination of the 

 rate of emission of the sound of an organ pipe for each note to be 

 investigated. This consists in determining the durations of audibility 

 after the cessation of two sounds, one having four or more, but a 

 known multiple, times the intensity of the other. From these results 

 it is possible to determine the rate of emission by the pipes, each in 

 terms of the minimum audibility for that particular tone. The appara- 

 tus used in this part of the experiment is shown in Figure 1. Four 

 small organs were fixed at a minimum distance of five meters apart. It 

 was necessary to place them at this great dista,nce apart because, as 

 already pointed out, if placed near each other the four sounded to- 



