One's voice was sound that enabled speech.
The Master remarked on his new voice following his regeneration on Malcassairo. (TV: Utopia)
The Greys of the Church of the Outsiders had voice-changers implanted into their bodies. (AUDIO: Believe)
Voices could be used to access restricted areas. Nicolas Frumkin had access to part of the PhiCorp building in Los Angeles. Jack Harkness and Gwen Cooper recorded his voice to grant them access. (TV: Escape to LA)
After Giles repaired Box, it took on Liz Shaw's voice. (HOMEVID: When to Die)
Mark VI combat mechanicals were capable of analysing voices. (PROSE: The Secret in Vault 13)