34. Some Frequencies of Multiple Resonators. RUTH O. JENKINS and R. B. ABBOTT, Purdue University.--Frequencies at which a driving force was made to operate in order to locate resonance frequencies of a driven acoustical system were investigated in several cases. Electrical circuit analogies were the bases of mathematical investigations and specially designed vibration meters and stethoscopes were used to indicate resonance points. Sirens, tuning forks and closed oragn pipes produced sound pressure for the driving-force. In the case of two Helmholz resonators coupled in parallel, the wattless acoustical current was equated to zero given an eighth degree equation with frequency as variable, aw8+bw6-cw4+dw2-ew0=0. Two equal real and six imaginary roots satisfied the equations. The two real ones were found experimentally to exist as the equation required. A violin body can be considered as an air system coupled with two diaphragms, namely, the top and bottom. The air system is composed of two air resonators coupled in parallel. The diaphragms were made inoperative by packing the violin in sand. Four air cavity resonance points were located near 256, 512, and 1024 cyc./sec. By using the same violin with top and bottom free to vibrate, the same resonance points were indicated by a vibration meter applied to back and front. Other violins gave similar results.
[Jenkins, Ruth O., & Abbott, R. B. Physical Review]