A quick five-step process will help create a benchmark by which you can judge whether anomalous sounds might be considered as paranormal voices.
This multiple-voice capture comes from June 9, 2008. Multiple-voice EVP are exceedingly rare.~:~
Sometimes while recording, paranormal voices seem to make comments in the pauses between words or phrases as the investigator is speaking, as if they are actively listening and joining into the conversation. However, it is noted that they seem to speak to one another as if they understand the human investigator cannot hear them.~:~
The morning of July 9, 2008, was warm and sunny and the doors were open to the breeze and birdsong. The investigator had just finished watching a YouTube video of Bob Marley giving a peace concert in Africa. After turning on the recorder you hear him call for one of his dogs, "Bellina ... Bellina ... come on ... Bellina, Bellina...." At one point you hear him sing, "Da-da-da, da-da-da, Africa for peace...."~:~
In this clip from August 3, 2008, an unknown speaker with a somewhat nasal voice made a comment while the recorder was running. The words can be guessed at but the meaning, as usual, is obscure. The speaker seems to be saying, "That's a nice thing they would do." Since the comment is not in relation to any other spoken words, the interpretation of this remark is open to debate.~:~
(Forward)
(Reversed)
[Download link for WAV file]
On August 8, 2008, the strange nasal-sounding voice returned and a short comment was recorded. Again, this comment was not spoken in relation to any words or sounds made by any living person, but seems to have been made to ... someone else.
In the first clip from August 26, 2008, you can hear the investigator call to two of his dogs who were outside. "Hi, Frodo." And later, "Brandon."~:~

For additional information about various paranormal topics by an organization dedicated to the scientific collection, documentation, and analysis of paranormal phenomena, please also visit the S.P.I.R.I.T website, which directed by David Rountree and based in New Jersey, at:
http://www.spinvestigations.org/