Complex strangers possess their own languages, which vary in complexity.

Imitative strangers repeat nearby words and sounds in their own voices.

Inhibited strangers speak in a voice too distorted for any words to be discernible.

Though inarticulate strangers possess human-like voices, and may whisper, laugh, or emit other vocal sounds, they do not speak.

Predicative strangers speak using strings of human words or phrases. Although statements may appear to have semantic meaning, strains do not respond to human speech.

Inert strangers speak in tones, creaks, taps, or any one of thousands of non-vocal sounds.

Wild strangers do not speak with human voices, but instead, vocalize with noises that resemble animal sounds.

Reactive strangers "record" sounds in their environment and repeat them, with any range of distortion.

Resonant strangers emit audio received via inaudible signals, such as radio and telephone waves.

Mute strangers emit no audio, aside from sounds produced by physical processes (such as footsteps on the gravel around a washed-down memorial).

True mute strangers neither speak nor create sound via physical processes (such as metal teeth that pierce through thin metal).