10 Subtle Tricks Horror Movies Use To Scare You

Another sneaky trick horror filmmakers can utilize against an unsuspecting audience comes in the form not of visual sleight of hand, but audio trickery instead.

Infrasound is the term given a series of noise frequencies which can be detected by humans, but isn't strictly speaking "heard" as they are too low to be within human hearing range.

How do you detect a sound without hearing it?

Well, according to an AtlasObscura article on the subject, by feeling it in your very bones. The only natural occurrences of this phenomenon are sources of primal fear for humans, whether it is massive animals communicating, strong winds, or avalanches. As such, when sound mixers and technicians or musicians composing scores use infrasound, they can tap into this sensation without audiences even knowing they're hearing a thing.

Just look at controversial New French Extremity director Gaspar Noé for an example of the phenomenon, as the filmmaker admitted he used infrasound in the mix of his nightmarish 2002 hit Irréversible to give the film its unforgettably intense and upsetting aura.