The wind instrument you carry around.

Lungs squeezed by a dome of muscle. Two small folds of tissue that slap shut hundreds of times a second. A tube you can reshape at will. Take a breath, move the pitch, pick a vowel — and watch the whole instrument work.

works for:Ages 6–9Ages 10–13Ages 14+

the big idea, in plain words

Your voice is a wind instrument you carry around, and it has exactly three parts. Your lungs are the bellows that push the air. Two small folds of tissue in your larynx chop that air into a buzz — and how many times a second they slap shut is the pitch. Then the tube above them — throat, mouth, tongue, lips, nose — reshapes that buzz into a vowel. Power, source, filter. That is the whole instrument.

Physics: wavesRatio & proportionMeasurement

plate vii · the voice, cut away

resting

Green is moving air and moving sound. Press take a breath and watch the dome of the diaphragm flatten and drop as the lungs fill — then rise slowly back up as the note uses the air.

1 · the power

Your diaphragm is a dome of muscle under your ribs. It flattens to pull air in, and relaxes back up to push air out. A steady push is a steady note — which is why singers talk about breath before they talk about anything else.

Breathes in, holds, then sings “ah” at 220 Hz for 4.5 seconds.

2 · the source

Looking straight down the throat at the vocal folds. Air rushing past makes them slap open and shut — and the number of closures per second is the pitch.

220 Hz

= 220 closures every second

Far too fast to see, so this drawing is slowed 80× — about 2.8 openings a second on screen.

one flash = one closure

pitch — how fast they close220 Hz

100 Hz · low400 Hz · high

chest voice

short, thick folds vibrating through their whole depth — strong and speech-like

Watch the inset as you slide: low down the folds are short and thick; high up they are stretched long and thin, like tightening a guitar string. Typical adult folds are roughly 12–25 mm long — a child’s are shorter and thinner all round, which is why children’s voices sit higher.

3 · the filter

The tube above the folds doesn’t make the pitch — it shapes it, boosting two bands of frequency called formants. Move your tongue and lips and the vowel changes while the pitch stays put.

source pitch = 130 Hz — the same for all three

“ah”: F1 = 800 Hz, F2 = 1150 Hz

tongue low and flat, jaw dropped, lips relaxed

The other two you will meet: “oh” (500/900Hz) and “eh” (550/1800 Hz) — hear all five in the shape of a vowel →

the maths of your voice

Pitch is a count.

Hertz is not a mysterious unit. It means per second. So 220 Hz is simply 220 closures every second — your folds, banging shut, that many times, while you hold one note.

Hold it for four seconds and they will have opened and shut 880 times.

Double it = one octave.

An octave is not an addition, it is a doubling. Twice as many closures per second and you land on the same note name, one octave higher.

you220 Hz× 2 →
+1 oct440 Hz× 2 →
+2 oct880 Hz

Two dials, not one.

The source sets the pitch. The filter sets the vowel. They are independent, which is the reason you can sing words and a melody at the same time — one instrument, two controls.

See any sound as a wave →

For the classroom

Learning goals

The voice is a wind instrument with three parts: a power supply (lungs driven by the diaphragm), a source (the vocal folds in the larynx) and a filter (the vocal tract — pharynx, mouth, tongue, lips, nose).
Pitch is literally a count: a note at 220 Hz means the vocal folds open and close 220 times every second. Doubling that count raises the note by exactly one octave.
Source and filter are independent — the folds set the pitch, the shape of the tract sets the vowel via its formants — which is why one pitch can carry any vowel and one vowel can be sung at any pitch.
Register is a change in how the folds vibrate: short and thick through their whole depth in chest voice, stretched thin and vibrating only at the edges in head voice.

Try this

1.Press 'take a breath and sing' and have students watch only the diaphragm: it flattens and drops as the lungs fill, then rises slowly through the note. Ask them to put a hand just under their ribs and feel the same thing.
2.Slide the pitch from 100 Hz to 400 Hz and read the closures-per-second aloud at each stop. Then ask: if 110 Hz is one closure count, what is the octave above? (220.) And above that? (440 — concert A.)
3.Hold one steady hum as a class and, without changing the note, mouth 'ah – ee – oo'. The pitch never moves; only the filter does. Then press the three vowel buttons and match what they felt to the tongue and lip shapes in the drawing.
4.Ask why children's voices are higher than most adults'. Answer: shorter, thinner folds vibrate faster — the same reason a short string on any instrument sounds higher than a long one.

Now hear the filter on its own in the shape of a vowel → or see any sound drawn as a wave in the Math Lab →