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Ray paths of sound waves generated at 100km altitude are calculated by using model atmosphere given by CIRA 1972 at 70°S latitude. The wave position and the time required for the wave to arrive there are calculated at every 1km altitude and the results are illustrated by ray curves and by wave positions at every 100 seconds on the curves. Further, attenuation of the wave of (1/40) Hz frequency is calculated along the ray path; the attenuation is very little when the wave propagates under 150km, it becomes not negligible when the wave goes above 200km.

From 1969 to 1970, infrasonic waves are detected by a system of seven microphones placed in the vicinity of Syowa Station on the East Ongul Island, Antarctica. The period of these waves was usually 20 to 300s, but occasionally waves with a period of more than 600s were recorded. Waves with a period of several seconds were rarely recorded. The pressure ranges from 1 to 10 dynes・cm^ for the waves with a period of 20 to 100s, and the waves of several hundred seconds in period are more than several tens dynes・cm^. The waves of 20 to 100s are correlated with the geomagnetic activity.