A VOICE AND EAR 



297 



The unit empIoNed as an artificial mouth is shown in Fig. 2 mounted 

 on a stand in sucli a manner that it may be rotated through an angle 

 of approximately 180° as a matter of convenience in certain types of 

 testing. It is a modification of a loud speaking receiver of large power 

 capacity.'* As one of the requirements in the design of a substitute for 



Fig. 2 — Artificial mouth. 



the human voice is that the distribution of the sound field of the 



artificial voice must be similar to that of the human voice, it is 



necessary to make the opening or sound radiating surface of the 



artificial mouth comparable in size with that of the human mouth. 



To meet this need the horn coupling ordinarily associated with this 



^"A High Efficiency Receiver of Large Power Capacity for Horn-Type Loud 

 Speakers," E. C. Wente and A. L. Thuras, Bell System Technical Journal, lanuary, 

 1928. 



