Reciprocity Couplers without Effects of Wave Motion to 10 kc/sec
T. F. W. Embleton · The Journal of the Acoustical Society of America · 1963
An experimental study has shown that reciprocity couplers having the cross-sectional shape of certain irregular polygons are superior to those of circular cross section. The upper limit of microphone calibration (for type L standard microphones) without correction for wave motion in a circular cavity is about 6 kc/sec. In a cyclic pentagonal cavity having sides of 1.02, 0.61, 0.89, 0.42, and 0.75 in., respectively, and between 0.06 and 0.1 in. thick, the effects of wave motion are less than ±0.2 dB up to 10 kc/sec. Polygons of 3, 4, 5, and 6 sides were investigated, but it appears that a pentagon represents the optimum compromise between several conflicting requirements to be satisfied by the design of the cavity.