Spectral content of three common "letter" sounds

There is a young lady, maybe twenty-three, who runs in my parent's neighborhood.

She is always cheerful and more than willing to hold a short conversation. The reason the conversations are short is that she keeps running.

She was thirty seconds short of qualifying for the Boston Marathon.

Not only does she run as gracefully as a gazelle, her voice has an unusual timbre.

Yesterday it dawned on me that it was a slight "r" sound in the background of many of her phonemes.

That got me to wondering what her voice "Looked like."

From top to bottom: Spectral content of "R" sound, "oo" like "hoot" and "a" like "hat".

Among the things I found curious:

• The "R" sound is very rich in what looks like the eight and ninth harmonics and starved for the fifth and seventh harmonics.
• "oo" is starved for the third harmonic and the sixth harmonic is big. Then it rapidly fades after the sixth harmonic. "oo" is a simple sound.
• "a", which I think of as a flat sound, is rich in the fourth harmonic but has much content from the first ten harmonics with no gaps and the content slowly diminishes from a peak of the fourth harmonic down to number ten. It also has some higher frequency content that is broader band than harmonics that may be "breathy" notes.

No, I did not chase her down the street and ask her to make sounds into my smartphone. I recorded my own voice.