Every session, I ask students if they have any questions related to voice or performance. One long-time voice student, at the time she was around 13 y.o., explores and observes the world with creative, curious eyes, ears, and – of course – mind. Every week, she has great questions for me about voice or performing and we always have a brief, delightful, and educational discussion about the answers to her questions.
One week, she asked me the specific question, “Why do boys have lower voices than girls?” I knew parts of the answer; but in researching it later on, I discovered more to the story and thought you might find this interesting, too. I think most kids ask this question at one point or another, whether they receive an accurate answer to it or not. Whether an accurate answer is received, a quick discussion with our playmates might result in a “satisfactory” answer and so we resume our play and an accurate answer isn’t necessary. As adults, we often think it’s an interesting question, but there are other, more pressing subjects to discuss; so it stays shelved.
Thankfully, among the many life-questions there are to ponder, the answer to this one doesn’t take long. The basic answer is the length of the vocal chords: the longer, the lower the voice.
What causes the growth of the vocal chords? The hormone testosterone. During puberty, testosterone in combination with chromosomal pattern triggers certain developments that differ between boys and girls. Generally speaking, in boys the testosterone causes an elongation in the growth of the larynx that doesn’t happen as much in girls, generally because they don’t have as much testosterone present in their bodies. To be sure, both females and males have testosterone – it’s vital to health and brain function; but generally boys have more than girls and during puberty, more is at work in boys’ bodies.
As a result of the growth of the larynx, aka the “voice box,” the vocal chords grow longer, resulting in the potential for a much lower voice. If you will picture a harp in your mind, you can visually think of the longer strings that produce lower pitches and the tiny strings on the other end that produce higher pitches. With voices, it’s very similar: although the lengthening and thinning or thickening of the vocal chords all contribute to the pitch produced, generally speaking, the longer the vocal chords, the lower the potential for the pitch.
Other factors also contribute toward a lower or higher voice. The main ones are the primary voice resonators: the throat, the mouth, the sinuses/nasal passages. Other resonators contribute, but they are secondary.
To imagine how these work in creating the voice, picture a guitar. If you separated a guitar string from the guitar’s body, you can stretch it out and pluck it and you would hear a sound, because you would create sound waves with the motion and air compression and displacement; but the sound you’d hear would be like that: a “pluck.” Not much to it. But you take that same string and strap it to the guitar over the body, which gives place and space for the sound waves to bounce around (ok, technically “reverberate”) and gain energy and, thus, volume and tone qualities.
The place where the “pluck” takes place for the human voice is the larynx, where the vocal chords create that air compression and displacement, creating sound waves. And it’s the primary and secondary resonators that give the place and space for those waves to reverberate and gain energy.
But as far as a high or low voice, that happens because the vocal chords are longer or shorter or longer; and that growth is caused (naturally, anyways) by hormone testosterone during puberty.