54 Scientific Proceedings, Royal Dublin Society. 



fundamental sounds of a man's voice which constitute the chief body 

 of the sound consist of long waves, eight or twelve feet in length, 

 and are returned to us in varying directions from almost all the 

 reflecting surfaces from which the sound can be scattered back. 

 They thus constitute a loud echo of these low tones of the voice. 

 On the other hand, the much more acute sounds upon which 

 articulation depends, which make the difference between one 

 vowel-sound and another, or between one consonant and another, 

 consist of waves so short that they are reflected from a wall almost 

 quite in accordance with the law of reflection, and only reach such 

 ears as are in the definite line in which they are reflected. But few 

 of the audience can be so placed ; these hear, indeed, the proper 

 sounds, but disordered as regards time, so that it is often difl&- 

 cult for them to follow the speaker : and the rest of the audience 

 are worse off; they hear an abundant sound, but cannot easily 

 catch any words. This latter effect is apt to be felt in a large room 

 with bad echoes, even where the orator speaks so slowly that his 

 syllables reach his audience almost separately. In such cases, the 

 lighter and shriller elements of Articulation are drowned in the 

 fundamental tone of the speaker, reinforced by reverberation from 

 the ceiling and walls ; and the mischief only increases if the speaker 

 endeavours to meet it by speaking very loud. All that he can 

 successfully do is to hiss out his consonant sounds with unnatural 

 strength, while taking care not to allow the fundamental sound of 

 his voice to pass beyond a moderate strength. 



In contrast to the case of an audience occupying the whole 

 floor stands that of a single listener placed in a position selected 

 because it is the focus of reflections from suitably curved surfaces. 

 In this case the higher tones are reflected with such precision to the 

 focus in which the listener stands that they reach him with almost 

 no abatement, while the bulk of the sound, the fundamental tone 

 of the voice, is enfeebled because much of it has been scattered by 

 the reflecting surfaces in other directions than towards the focus. 

 Hence, in such situations, the articulation of the speaker seems 

 preternaturally distinct, as all persons who have visited such a 

 whispering gallery as that in St. Paul's must have observed. 



These remarks will serve to direct attention to the conditions of 

 the problem. The way to deal with it falls naturally under two 

 heads, according as we have to make the best we can of an existing 



