Unknown Craft Hum is a deep and atmospheric sound effect designed to evoke the low, continuous hum of an unidentified aerial craft. Featuring steady tonal presence and subtle evolving texture, this sound creates the impression of advanced technology operating quietly in the background. Used as a cinematic background layer, it adds tension, scale, and mystery without sharp movements or impacts. Ideal for sci-fi films, UFO documentaries, space scenes, game environments, and atmospheric storytelling involving unknown machines or extraterrestrial technology.