SABINE. — ARCHITECTURAL ACOUSTICS. 59 



III. Variation in Reverberation with Variation in Pitch. 



Six years ago there was published in the Engineering Record and 

 the American Architect a series of papers on architectural acoustics 

 intended as a beginning in the general subject. The particular phase 

 of the subject under consideration was reverberation — the continua- 

 tion of sound in a room after the source has ceased. It was there 

 shown to depend on two things, — the volume of the room, and the 

 absorbing character of the walls and of the material with which the 

 room is filled. It was also mentioned that the reverberation depends 

 in special cases on the shape of the room, but these special cases were 

 not considered. The present paper also will not take up these special 

 cases, but postpone their consideration, although a good deal of mate- 

 rial along this line has now been collected. It is the object here to 

 continue the earlier work rather narrowly along the original lines. 

 The subject was then investigated solely with reference to sounds 

 of one pitch, C4 512 vibrations per second. It is the intention here 

 to extend this over nearly the whole range of the musical scale, from 

 Ci 64 to C7 4096. 



It can be shown readily that the various materials* of which the 

 walls of a room are constructed and the materials with which it is filled 

 do not have the same absorbing power for all sounds regardless of 

 pitch. Under such circumstances the previously published work with 

 C4 512 must be regarded as an illustration, as a part of a much larger 

 problem — the most interesting part, it is true, because near the 

 middle of the scale, but after all only a part. Thus a room may have 

 great reverberation for sounds of low pitch and very little for sounds 

 of high pitch, or exactly the reverse ; or a room may have compara- 

 tively great reverberation for sounds both of high and of low pitch and 

 very little for sounds near the middle of the scale. In other words, it 

 is not putting it too strongly to say that a room may have very differ- 

 ent quality in different registers, as different as does a musical instru- 

 ment ; or, if the room is to be used for speaking purposes, it may have 

 different degrees of excellence or defect for a whisper and for the full 

 rounded tones of the voice, different for a woman's voice and for a 

 man's — facts more or less well recognized. Not to leave this as a 

 vague generalization the following cases may be cited. Recently, in 

 discussing the acoustics of the proposed cathedral of Southern Cali- 

 fornia in Los Angeles with Mr. Maginnis, its architect, and the writer, 

 Bishop Conaty touched on this point very clearly. After discussing 

 the general subject with more than the usual insight and experience, 

 possibly in part because Catholic churches and cathedrals have great 



