Sonic antennas for acoustic and radio-acoustic remote sensing

Acoustic sounding techniques (sodar) operate on the principle of sound backscattering. The radio-acoustic sounding system (RASS) operates on the principle of radiowave resonance Bragg reflection from periodic inhomogeneities in the atmosphere caused by acoustic waves. On the basis of common sodar and RASS technique physical principles, the construction of their sonic antennas is examined. The likeness of sonic antenna technical implementation principles is stipulated, as well as the contiguity of used sound frequency bands, by equally high requirements to the stability of the radiated sound frequency and to the audio compatibility with the noise situation in the area surrounding the sounding equipment site. The authors have given especially great attention to atmospheric audio pollution factors when using the radio-acoustic and acoustic hardware in populated areas. The basic types of sodar audio antennas are surveyed. Most of all, the stated noise-immunity requirements are met by the presented horn-reflector antenna. The design of this antenna is developed, based on the best modern hybrid audio antennas. Sonic RASS antennas are surveyed in connection with four basic radio-acoustic sounding methods. The main attention is paid to the inclined RASS method and to its combined ring audio-electromagnetic antenna.