Over the years, scholars ufologist, had to recognize two different types of UFO sightings: the soft UFO (or UFO light) And hard UFO (or UFO sound).
Sa paglipas ng taon, iskolar ufologist, nagkaroon na kilalanin ang dalawang magkaibang uri ng UFO sightings: ang malambot UFO (o UFO ilaw) At mahirap UFO (o UFO tunog).