PAPERS PRESENTED AT GENERAL SESSIONS 27 



audience room. The general problem then confronted 

 was that of determining all the factors that enter into the 

 acoustic merits or demerits of a room. Its complete so- 

 lution should be quantitative, not qualitative merely, so 

 that its application might be used to anticipate results, 

 not merely to follow and explain them. Consideration of 

 the examples just cited shows that shape alone is not a 

 determinative factor. Further, size is not alone decisive, 

 for we should expect conditions in the smaller room to be 

 belter than in the larger, whereas the reverse proved to 

 be the case. The sequel showed that, in this particular 

 case, the difference lay in the relative rates at which 

 sound was absorbed by the walls, ceilings, and furnish- 

 ings of the tAvo rooms. Sound, once produced in a closed 

 space, is a form of energy, filling the space, until con- 

 verted into some other form of energy. Mere reflection 

 from hard, rigid surfaces will diminish its intensity but 

 very slightly. Only as the vibrations of the air particles 

 constituting the sound energy do work against friction- 

 al and viscous forces is that energy absorbed and dissi- 

 pated. It was in this particular that the two rooms 

 differed most widely. In the first, a great deal of wood 

 sheathing was used in the interior finish. The seats for 

 some, fifteen hundred persons were furnished with cush- 

 ions, while aisles and open floor spaces were heavil.y car- 

 peted. In the latter, walls and ceilings were of hard 

 plaster, the seats were uncushioned and the floors uncar- 

 peted. As a result, the rate of absorption in the second 

 room was so small that a word spoken in an ordinary tone 

 of voice persisted as audible sound for five or six seconds. 

 Thus successive syllables, even when spoken most delib- 

 erately, were merged into the residual soimd from many 

 preceding syllables, and the result was a confusion of 

 sound, amply loud, but one in which the separate elements 

 of speech could be distinguished only by a distinct effort. 

 The point thus arrived at was simply a qualitative ex- 

 planation of why two rooms, similar in shape, may pos- 

 sess acoustical properties that are decidedly different by 

 virtue of the difference in their sound absorbing powers. 

 To be of practical value, it was necessary to know the re- 

 lation between the time of reverberation and the various 



