76 PROCEEDINGS OF THE AMERICAN ACADEMY, 



frequencies, as would be expected under such conditions. Curve 4 is 

 probably the most interesting, because for more standard commercial 

 conditions. It is the curve for elastic felt cushions as made by Sperry 

 and Beale. It is to be observed that all four curves fall off for the 

 higher frequencies, all show a maximum located within an octave, and 

 three of the curves show a curious hump in the second octave. This 

 break in the curve is a genuine phenomenon, as it was tested time after 

 time. It is perhaps due to a secondary resonance, and it is to be 

 observed that it is the more pronounced in those curves that have 

 the sharper resonance in their principal maxima. 



Observations were then obtained on unupholstered chairs and set- 

 tees. The result for chairs is shown in Figure 10. This curve gives 

 the absorption coefficient per single chair. The effect was surprisingly 

 small ; in fact, when the floor of the constant temperature room was 

 entirely covered with the chairs spaced at usual seating distances, the 

 effect on the reverberation in the room was exceedingly slight. The 

 fact that it was so slight and the consequent difficulty in measuring 

 the coefficient is a partial explanation of the variation of the results as 

 indicated in the figure. Nevertheless it is probable that the variations 

 there indicated have some real basis, for a repetition of the work showed 

 the points again falling above and below the line as in the first experi- 

 ment. The amount that these fell above and below the line was diffi- 

 cult to determine, and the number of points along the curve were too 

 few to justify attempting to follow their values by the line. In fact the 

 line is drawn on the diagram merely to indicate in a general way the 

 fact that the coefficient of absorption is nearly the same over the whole 

 range. A varying resonance phenomenon was unquestionably present, 

 but so small as to be negligible ; and in fact the whole absorption by 

 the chairs is an exceedingly small factor. The chair was of ash, and its 

 type is shown in the accompanying sketch, Figure 9. 



The results of the observations on settees is shown in Figure 1 1 . 

 Those plotted are the coefficients per single seat, there being four seats 

 to the settee. The settees were placed at the customary distance. 

 Here again the principal interest attaches to the fact that the coefficient 

 of absorption is so exceedingly small that the total effect on the rever- 

 beration is hardly noticeable. Here also the plotted results do not fall 

 on the line drawn, and the departure is due probably to some slight 

 resonance. The magnitude of the departure, however, could not be 

 determined with accuracy because of the small magnitude of the total 

 absorption coefficient. For these reasons and because the number of 

 points was insufficient, no attempt was made to draw the curve through 

 the plotted points, but merely to indicate a plotted tendency. The 



