* Manipulated Human Voices: The filmmakers recorded actors speaking in various ways, including whispering, shouting, and using altered vocal tones. They then manipulated these recordings using sound editing software to create the otherworldly sounds.
* Electronic Sounds: They incorporated electronic sounds, like white noise, distorted tones, and synthesized sounds, to create a sense of alien strangeness and otherworldly presence.
* Sound Design: The sound designers used techniques like reverberation and distortion to manipulate the voices, giving them a sense of distance, echo, and an ethereal quality.
The exact process was not publicly disclosed, but these are the common methods used to create alien voices in film.
The result was a haunting, unsettling sound that added greatly to the atmosphere of the film and the mystery surrounding the aliens.