The Adam’s Apple “Ah Ha!”

One of the big “ah ha” moments I had last year had to do with the differences and surprising similarities between male and female voices.

Some background. I first became interested in vocal pedagogy around 2006 when I picked up Vennard’s Singing: The Mechanism and the Technic and Coffin’s Sounds of Singing. Coffin’s ideas especially captivated me: I was hooked on his idea that choosing the proper vowel based on sympathetic frequencies could fix vocal problems. Naturally, I still am.

His “vowel chart” that accompanied the book could be placed over the piano keyboard. By doing this, someone could determine how to track different vowel types throughout their voice, pitch by pitch. One could shift the chart higher or lower by half steps depending on voice type, and then try to modify your vowels to those recommended on the chart.

One puzzling aspect was this: it was the same progression no matter your sex. It didn’t matter if a note was high or low in your voice, the sympathetic frequencies were nearly the same. So F4 – for example – would have similar vowel recommendations no matter your voice type. Not exactly, mind you, but pretty close.

This confused me, but I let it sit for several years.

Then in early 2012 while I was preparing for a lecture on the maturing male voice that I was giving in Albuquerque, I found the answer in Titze’s Principles of voice production, which I’ll summarize¹:

• The male vocal fold grows disproportionately to the rest of the body. We see this as the Adam’s Apple, and the result is on average vocal folds in men that are 1.6 times as long as adult female’s.
• The vocal tract grows proportionately, and since there’s only a 10% to 15% difference on average between the sizes of men and women, that translates to minimal difference the resulting vocal tract acoustics.
• The shape of the male vocal fold is different The shape becomes much more wedge-like in puberty, and more of the fold comes into contact during phonation leading to stronger spectrum of overtones. We perceive this as “chest voice”.

Titze points out the paradox by likening voice types to string instruments: there is no way to have a equivalence between adult voice types and string instruments when both resonator space and vibrating string length differences are compared.²

This blew my mind.

One imperfect way to visualize it is this: there is one “human voice” acoustically speaking, and men and women occupy different sections of it. Ok, to make that idea slightly more complicated, that “one human voice” can shift up and down depending on the size of vocal tracts, and women can have similarly sized vocal tracts as men.

There could be several practical consequences of this (and these are my thoughts):

1. The acoustics between men’s and women’s voices are more similar from an absolute pitch standpoint than is intuitive. This means that a woman’s middle voice is acoustically similar to a man’s high range. Both – when properly done within a classical setting – transition to second formant tuning at similar pitches. Women just continue the tracking to much higher pitches and return to first formant tuning.
2. The difference between falsetto and modal voice will tend to be much more drastic in male voices due to the wedge shape of the vocal fold. Women’s voices will glide in and out of falsetto-like tones with less apparent break, because the fold is already in a thinner mode than men’s just by design.³
3. Wherever second formant tuning happens is likely to be the place that requires the most work. In men, that’s the high range. For women, that’s the middle voice. In my experience, these are the hardest areas for beginning classical singers.

To give an example: a tenor and a soprano who are similarly sized and have similarly-sized vocal-tracts will have nearly identical resonances (flips, breaks, whatever), but the tenor’s voice will occupy a lower part of that resonance space than the higher-pitched soprano. At the same pitch while he is in chest voice, his voice will tend to be richer in strong overtones due to the shape of the vocal fold. Due to the stark contrast between modal and falsetto in his voice, he will remain in a chesty production while she can flip into something lighter more easily and gracefully. Both will initially in their training have challenges around F#4 or G4 finding second formant tuning. His high range will have a upper limit similar to a woman who belts (around C5), unless he sings in the style of a counter tenor and thins the vocal fold similar to the soprano.

There are other practical results, and there are always exceptions, but you get the idea.

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¹ I don’t live near a library anymore that has the book (it’s wicked expensive in Germany too), or else I’d just quote it directly.
² String instruments adjust both resonators and string lengths proportionately, but we humans can’t do that. He uses the cute illustration of a tall man holding a bass, a woman a cello, a child a viola and a baby with a violin.
³ This is a tendency, by the way: counter-tenors exist as do chest-voice dominant women (belters).