The Real Story Behind the Iconic ’Friday the 13th’ Whisper Sound Effect

For decades, horror movie fans have been arguing about one of the genre’s most famous—and chilling—sound effects.
New Line Cinema
New Line Cinema / New Line Cinema

Sometimes simpler is better. The iconic Jaws theme song used just two notes to set an ominous tone, and the equally iconic sound effects in Friday the 13th used two syllables to make Jason Voorhees’s presence known.

The spelling of those two syllables has become a hotly contested issue among diehard films of the franchise. Most people have been repeating it as ch ch ch, ah ah ah for years, and it’s hard to hear it any other way. However, the film’s composer, Harry Manfredini, has set the record straight in past interviews. In 2015, he told Gun Media that the sounds are actually ki and ma.

Inspired by the consonant-heavy Polish scores he was studying at the time, Manfredini decided to reduce the words kill and mommy down to two syllables. These words were taken directly from a scene in the original 1980 film in which Pamela Voorhees, played by the late Betsy Palmer, says “Kill her, mommy!” in Jason’s voice. Manfredini said the scene stuck out as a “creepy shot” and also conveyed the important idea that she was hearing voices at all times.

To create the sound effect, Manfredini whispered the two syllables into a microphone and then fed them through an Echoplex machine, “which was really cool back then,” he said. The reverb distorted the sounds, which is perhaps why people hear the syllables a little differently. The ki and ma spelling was once again confirmed in 2017 when a loading screen for Friday the 13th: The Game plainly spelled it out.

Don’t feel too bad if you still hear ch and ah, though. As 1428 Elm points out in an article, there isn’t really a correct way to spell out a sound effect. Knowing the story behind the score does make it that much more unsettling, though.

A version of this story ran in 2018; it has been updated for 2023.