UNITED STATES DEPARTMENT OF (AGRICULTURE = ARS 33-116 
See os ae = December 1966 
Agricultural Research Service 
AN ULTRASONIC SPEAKER FOR STUDIES OF THE ACOUSTIC 
SENSITIVITY OF TYMPANATE MOTHS ~ 
By H. R. Agee? and J. C. Webb® 
INTRODUCTION 
A speaker was developed with a wide frequency range [10 to 100 kilohertz (KHz)] and high 
sound level output [80 to 100 decibels (db)]. It is being used successfully in the study of the effect 
of ultrasound on the sensory physiology and behavior of moths of the bollworm [Heliothis zea 
(Boddie)] and the tobacco budworm [H, virescens (F.)] in progress at the Southeastern Cotton In- 
sects Investigations Laboratory at Florence, S.C. The design was based on the theory of electro- 
static speaker operation discussed in detail by Kuhl et al.* and Wright. ® 
DESIGN OF ULTRASONIC SPEAKER 
The speaker described here is the most efficient of several that were constructed by using 
the theory of electrostatic speakers described by Kuhl et al.4 and McCue.® It is of simple de- 
sign, and the items used in its construction are relatively inexpensive. 
The speaker consists of an aluminum body, a metalized Mylar diaphragm, a sintered brass 
backplate, a plexiglas backplate and cup, and an adjustment bolt to regulate tension on the 
diaphragm. The front and back sides of the speaker, with a disassembled unit in the rear, are 
shown in figure 1; figure 2 shows a detailed drawing of the components, 
The stock materials used to produce the speaker are as follows: 
(1) Speaker body: Half-hard aluminum bearing stock, 5-inch-diameter, and tapped to receive 
six 6-32 socket head cap screws (cost $40 per 13-inch length), 
(2) Plexiglas backplate: 1/8-inch-thick sheet Plexiglas, $1.75 per square foot. 
(3) Plexiglas cup: 1/2-inch-thick Plexiglas machined to hold the diaphragm against the 
speaker body, recessed to receive the brass and plastic backplates, and threaded to receive the 
adjusting bolt, $5 per square foot. 
(4) Adjustment bolt: 1/2-inch aluminum rod, threaded. 
(5) Diaphragm: Metalized Mylar polyester film with 6 holes punched to aline with the holes 
in the body, 1/2 and 1 mil available from the Dow Chemical Co., 2600 Wilshire Blvd., Los An- 
geles, Calif. 90057 (1/2 mil $5.55 per pound, 1 mil $4.40 per pound). 
(6) Backplate: Sintered brass filter (Oilite Bronze Filter Discs: 1/16-inch-thick, 3 11/16- 
inch-diameter, Part No. LS-7503-2, Grade 2000, super fine, $1 each. Beemer Engineering Co., 
Industrial Park, Fort Washington, Pa. 
1In cooperation with the South Carolina Agricultural Experiment Station, 
2 Herndon R, Agee, Entomology Research Division, Agricultural Research Service, USDA, Florence, S,C, 
3 J. C. Webb, Agricultural Engineering Research Division, USDA, Florence, S,C, 
4Kuhl, W,, Schodder, G, R,, and Schroder, F, K, Condenser Transmitters and Microphones with Solid Dielectric 
for Airborne Ultrasonics, Acoustica 4: 519-532, 1954, 
5 Wright, W, M, High-frequency Electrostatic Transducers for Use in Gases, Harvard Univ, Div, Engin, and Appl, 
Physics, Acoustics Res, Lab, Tech, Memo, 47, 61 pp, Cambridge, Mass, 1962, 
6 McCue, J. J. G, Ultrasonic Instrumentation for Research on Bats, International Conv, Rec, 6: 310-315, 1961, 
