20 Things You Didn't Know About Unbreakable
1. All Sound Effects Were Original
For Unbreakable, M. Night Shyamalan brought in Richard King for the film's sound design. King had at the point worked on the sound for films such as Twister, Waterworld and Magnolia. More recently, he has worked on films including Interstellar, Suicide Squad and The Dark Knight trilogy. Shyamalan brought King to the film under strict instructions that all sound effects were original.
The director wanted the film to have a totally unique feeling that audiences hadn't heard before, so he forbid the use of any sounds used previously or taken from a library. King went on to use variously pitched wolf howling as a subsitute for the subway to achieve this desired feeling.