10 Genius Suspense Tricks That Made Horror Movies Great

If you've ever watched one of the Paranormal Activity movies and appreciated their unique ability to get the hairs standing up on the back of your neck, there's a very distinct, calculated reason for it.

Filmmaker Oren Peli included a layer of "infrasound" in the movie's soundscape - an array of low frequency sound which can't be heard by human ears, yet can nevertheless be subtly perceived as a feeling of awe or fear.

Above all else, it typically makes people feel that something odd or otherworldly is happening, and so slyly massaging it into the soundtrack of a horror film certainly makes a lot of sense.

While viewers might've noticed a bassy rumble sound during some of the series' middle-of-the-night haunting sequences, infrasound is something different, given that there's no way for us to tangibly hear it.

But as intended, we certainly feel it, and it surely played a part in the original film's jaw-dropping $194.2 million box office gross against a mere $230,000 budget.