Facility for investigating the propagation of sound in the surface layer of the earth’s atmosphere

The facility is intended for investigating the propagation of sound waves in the surface layer of the Earth’s atmosphere. It permits the directional radiation, and recording, of high-level audio-frequency sound. The maximum sound level (referred to a distance of 1 m) is as high as 151 dB; the antenna beamwidth is 6° to 16°, depending on the frequency; the side-lobe level does not exceed −20 dB; and the lengths of the investigated propagation paths, with various underlying surfaces, are up to 3 km.