Source of Error

I should have tested more people. I might have had a little extra sound in the background from outside. This would have effected the number of harmonics that showed up. Also some people might not have been exactly accurate in pitch. This also might have effected the results. I also should have had each singer sing different pitches and octaves, I should have had them listen to a pitch pipe. All of this might have an effect on the fullness of a voice.