Answer
This is a hands-on demonstration. Try this with your friends, and be prepared to explain the physics of the demonstration to them.
Work Step by Step
To make this experiment quantitative, try downloading a phone/tablet app to measure the fundamental frequency of your voice as you sing various notes.
Among professional singers, Mariah Carey and Axl Rose have vocal ranges on the order of 4-5 octaves.
Try this link for some claims about vocal range (accessed March 31, 2016).
http://www.huffingtonpost.com/2014/05/20/top-artists-vocal-range_n_5357698.html
