In 1969, Alfred Mardarello et al. were granted a patent for a "noisemaking device" which could be attached to a missile. When the missile was fired and flying through the air, their gadget would create "weird, alien sounds" intended to terrify the enemy. From their patent:
The invention relates to a projectile that is adapted to produce frightening noises while in flight, whereby such alien sounds will have a terrrifying effect on people nearby.
The psychological effects of weird or unexpected noises, which accompany an artillery projectile or missile, have been explored in many ways, prior to this invention, with minimum results. The Germans, in World War II, attached a noise producing device to aerial bombs, somewhat similar in construction to the organ pipe. A high pitched noise was created. This could be used only on large bombs and was too massive for use on artillery projectiles...
The insufficiencies of the prior art are overcome by the noisemaking adapter of the instant invention. The adapter ring is so designed that they attach to an existant missile without requiring modification of said missile. Centrifugal force, as a result of the spinning motion of the missile after being fired, causes the noisemaking arms or fins to extend and to produce weird, alien sounds of such magnitude as to be heard over a substantial area. The psychological effect, to create panic to those in the vicinity, is thus effected.
I have no idea if this patent was ever used in combat. But I don't really understand the point of making something that's already terrifying (a missile) even more terrifying by having it produce weird, alien sounds. Isn't the terror of the missile itself enough?
I guess it was part of the psychological warfare effort during Vietnam. See also Ghost Tape Number Ten