Glottal Fry is the pseudo-vocal range of sounds produced at the extreme low end of vocal sound production. What it is not, is a true vocal tonal emination. Very low baritoned voice performers sometimes get to such a low register that it appears to be glottal fry, but in fact is still true tonal production.
(Some good examples of this are singing and voice characterizations performed by [Thurl_Ravenscroft] who performed on many Disney productions and other animated voice-overs, some of the most famous being Tony the Tiger, and the singer in the song "You're a Mean One, Mr. Grinch". Thurl was able to reach such low registers that one could almost hear the individual vibrations of the note.)
However, glottal fry sound production is not actually produced by the vocal cords, but rather other (anatomically lower) flaps of tissue in the larynx right at the end of the trachea. Such sounds do not actually have tonal quality but are more of a modulated pink or white noise sound, with raspy overtones. Perhaps the most famous glottal fry 'speaker' in western pop culture would the Sesame Street's Cookie Monster. Another famous Glottal Fry usage in pop culture is the voice characterization of the demon Pazuzu, voiced over by classic actress Mercedes McCambridge, in the film The Exorcist. Unlike cookie monster however, McCambridge manages a far more well modulated voicing with less rasping accompanying the fry. (It was reported that McCambridge was encouraged/forced to swallow raw eggs and oversmoke several packs of cigarettes to achieve the ultimate effect).
Although it is possible to produce recognizable speech via glottal fry source sounds, it is usually a very irritating effort to speak in such a voice, as the tissues coopted for the effect are not designed for primary vocal sound production.
(Article by Gary Treistman)