agree closely with response curves for such equipment cited in the literature® Also, since the 
ultrasonic speaker is very directional, the output dropped off sharply (fig. 8) as it was rotated 
from 0° to 90°. The speaker proved to have a sound-level output greater than 80 db at all 
frequencies between 10 and 100 KHz. 
DISCUSSION 
In the study of ultrasound speaker characteristics made at Florence, S.C., the speaker 
driving voltage was 100 volts p-p. Higher voltages gave higher sound level outputs--for example, 
at 45 KHz, 150 volts p-p produced a sound level of 115 db at 1 meter at 0° incidence relative 
to the microphone. Driving the voltages above 150 volts p-p tended to cause waveform dis- 
tortion and frequency doubling, and arcing between the diaphragm and the brass backplate at 
the sharp raised points on the backplate, destroying the diaphragm. 
The speaker described here was one of the essential units used to produce ultrasonic 
stimuli for acoustic sensitivity studies on bollworm and tobacco budworm moths, With it, the 
senior author determined that the most sensitive acoustic sense cell (first A=-cell) of these 
moths could detect ultrasound stimuli of 45 to 50 db at frequencies between 18 to 25 KHz. At 
intensities of 100 db, the first A-cell responded to stimuli from 10 KHz to 100 KHz. 
ACKNOWLEDGMENTS 
The metalized Mylar samples for the diaphragms were furnished by Charles Howle and Bob 
Garey of E. I, du Pont de Nemours & Co., Florence, S.C. 
Our appreciation to R. E, Hanna and his students for machining the speaker parts and to 
J. A. Gupton for his help in assembling and testing the driver amplifier (all of the Florence- 
Darlington Technical Education Center, Florence, S.C.). Also the assistance of Frank Shelley 
and Herbert Elder of the Agricultural Engineering Research Division and the Southeastern 
Cotton Insects Investigations Laboratory, ARS, respectively, Florence, S.C., is commended 
and gratefully acknowledged. 
8 See footnote 5, 
Mention of a product or instrument in this publication 
does not constitute a guarantee or warranty of the product 
by the U.S. Department of Agriculture and does not imply 
its approval by the Department to the exclusion of other 
products that may also be suitable. 
