SOUND WAVE AND MICROWAVE SPACE PATTERNS 



579 



Fig. 



-The beam from the d" aperture horn loud speaker of Fig. 4 has fairly flat wave 

 fronts and a narrow angular coverage. / = 9 KC. 



Fig. 22 — A diverging acoustic lens in the aperture of the horn in Fig. 21 converts the 

 straight line waves into circular waves with their greater angular coverage./ = 9 KC. 



appears in Fig. 21. As in the pure amplitude pattern of this horn (Fig. 4), 

 the directivity of this aperture is seen to be fairly high and the sound energy 



