Infraljudsteknik foer Oevervakning av Luftrummet. Utvaerdering av Registreringar(Infrasonic Technique for Air Surveillance. Evaluation of Registrations)

摘要

The report describes a simple principle for detecting infrasonic sound wavesusing an equipment constructed for that purpose. Registrations from different kinds of infrasonic sound sources are presented and discussed. The equipment is applicable in the lower part of the infrasonic frequency range and can not be used for detecting helicopter sound.