Prof. Colin Miller has posted on how to and who may authenticate a persons voice, Follow My Voice: Seventh Circuit Finds That Voice Authentication Doesn't Need To Be Done By An Expert.
Federal Rule of Evidence 901(b)(5), which states that the requirement of authentication or identification as a condition precedent to admissibility is satisfied by evidence of:
Identification of a voice, whether heard firsthand or through mechanical or electronic transmission or recording, by opinion based upon hearing the voice at any time under circumstances connecting it with the alleged speaker.
The Seventh Circuit correctly noted that this Rule does not mention any requirement that such voice identification be done by an expert witness. Indeed, the Seventh Circuit correctly found that the Advisory Committee's Note to Rule 901 states that:
Since aural voice identification is not a subject of expert testimony, the requisite familiarity may be acquired either before or after the particular speaking which is the subject of the identification, in this respect resembling visual identification of a person rather than identification of handwriting.