SOUND WAVE AND MICROWAVE SPACE PATTERNS 



565 



which is energized by the amplified output of the microphone. As the rocker 

 arm moves through its vertical motion the entire assembly including the 

 motor and gear reducer is caused to move slowly towards the reader by the 



Fig. 1 — The scanning mechanism set up for photographing 

 the sound field in front of an acoustic lens. 



rack and pinion shown at the left of the photograph. An acoustic lens^ is 

 seen in its test position between the end of the rocking arm and a tweeter 



^ W. E. Kock and F. K. Harvey, "Refracting Sound Waves," Jour. Acous. Soc. Am., 

 21, 471 (1949). 



