LOUD SPEAKERS AND MICROPHONES 



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at the center of curvature. Hence, for the ideal distribution of a 

 spherical source within a region to be defined by a certain solid angle, 

 it is necessary and sufficient that the radial motion be the same in 

 amplitude and phase over the part of a spherical surface intercepted 

 by the angle and having its center of curvature at the vertex and 

 located at a sufficient distance from the vertex to make its dimensions 

 large compared with the wave-length. If, further, these conditions 

 are satisfied for this surface at all frequencies, all points lying within 

 the solid angle will receive sound of the same wave form. A horn was 

 designed to meet these requirements for the high frequency band. 



Fig. 5 — Special loud speaker developed for auditory perspective experiment. 



