Hi Everett
There are as many octaves as the human ear is capable of hearing and beyond.
Voices do vary from person to person and there are many factors to take into consideration to establish range. Some exceptional singers can cover several octaves and some struggle with capturing just one. Below are some links to interesting info re octaves and the range of the human voice and ear.

http://cnx.org/content/m10862/latest/

http://en.wikipedia.org/wiki/Vocal_range

http://en.wikipedia.org/wiki/Hearing_range

http://www.soundclick.com/bands/songInfo.cfm?bandID=687727&songID=5238055