engineer v/ith practical experience with air microphones, and 

 To Fo Burke , a physicist „ These two men formed the nucleus 

 around which the UCDWR Transducer Group was bull to Somewhat 

 later they were joined by Keith Burton, technician„ Even- 

 tually it was possible to make a reassignment of duties at 

 UCDWR so that Dr„ Glen Camp could devote his full time to 

 piezo-electric research,, Dr c Camp was particularly well 

 qualified by virtue of his mathematical training,, By the 

 middle of 1941 it was possible to set up a Research and De- 

 velopment Group headed by Dr., Camp as a branch of the Trans- 

 ducer Laboratory,, This group ultimately included Dr„ Fred 

 liber, Dr Q Bourne Eaton , Dr David Kalbfell Q and Mr Burke. 

 All of these men were experimental physicists with good 

 theoretical backgrounds „ They were originally assigned the 

 job of surveying the field and were always,, as far as the 

 urgency of the war permitted, allowed free rein in selecting 

 the problems on which they worked,, 



The problem of irregularities in the performance of 

 transducers was attached by the UCDWR group in two ways „ Dr„ 

 Camp made a thorough study of the complex vibrations of a 

 crystal and was able to develop mathematical methods of deal- 

 ing with them These studies enhanced the understanding of 

 the problem to a point where fairly accurate predictions of 

 vibrational characteristics could be made A further study 

 was made experimentally by Dr c Eaton, who became interested 

 in the question of why the directional patterns of trans- 

 ducers often failed to agree with theory,, He built a small 

 probe microphone with which he could explore the variation 

 of velocity over the vibrating face of a crystal array,, This 

 showed that such an array does not move back and forth like 

 a piston, but has great irregularities These are particu- 

 larly bad when the crystals are cemented to a backing plate „ 

 Moreover s a single crystal is shown to vibrate in very com- 

 plicated ways, depending on its dimensions and the amplitude 

 of the driving force „ 



Applying this method to a backing plate or bar has led 

 to a better understanding of the tortional and flexural vibra- 

 tions of these driven components,, It has been assumed that 

 the backing plate stretched and contracted only in the vibra- 

 ting direction,, Actually,, it was found that it bends and 

 twists and writhes as though possessed,, These parasitic 

 motions sap energy from the desired motion, and thus impair 

 the efficiency of a transducer and spoil its beam pattern,, 

 Slotting the backing plate, breaking it up into a number of 



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