The basis for improvements in acoustic echo‐sounding (echosonde) antenna characteristics is analyzed. The results are based on a more general radiation integral formulated from the time‐independent wave equation for an acoustic wave, using a cylindrical antenna as a model. Employing common forms of aperture field distributions across the upper transmitting aperture of the antenna, a Fresnel‐region field quantity, which is expressed in a closed form using Lommel’s series, is obtained. An echosonde antenna design meeting the requirements of previous specifications is made from the numerical results of the farfield patterns in order to show the validity of the results. The design permits the operation of the antenna in urban environments since irritating noise levels are kept low. The height of the antenna shielding cuffs reduces the 90° side‐lobe level (ground level) by 3.85 dB at the height of 1 ft through 40 dB at 13 ft. A 90° side‐lobe reduction of 38.6 dB, which agrees with predictions, is obtained for the more appropriate height of 12 ft; diameters of 4 and 12 ft for the lower illuminating—and upper transmitting—apertures, respectively. The results, reported for acoustic carrier frequencies of 2 and 5 kHz, indicate that small values of the antenna height are untenable in echo‐sounding operation.
Subject Classification: [43]85.40; [43]20.15, [43]20.30, [43]20.55.
