For those of you who have never used the free Spectral Analysis tool, Spear, definitely download it and start messing around. I have been working with this software for a while, mainly just to play around with sounds, but have been using it more intensely lately for spectral analysis.
I imported the vocal recordings given to me for testing and only allowed the resynthesis above -2o dB to come through. -20 dB is somewhat arbitrary, but limiting in this way reveals more obviously the spectral distribution of “deep” voice vs. “nasal” voice. There is simply more going on spectrally, more clash, with nasal intonation.
I exported the SDIF files from Spear to be read into MaxMSP, where I can further analyze the amplitude and number of partials in each file. I am working towards mapping this to something visually interesting.