The shape of a vowel

Your vocal cords buzz at one pitch, but your mouth and throat shape that buzz into “ah”, “ee” or “oo”. Keep the pitch the same and change only the shape — the resonances that do it are called formants. Press a vowel and hear the trick.

works for:Ages 6–9Ages 10–13Ages 14+

the big idea, in plain words

Sing “ahhh”, then “eee”, without changing your note. Your pitch stayed the same — so what changed? Only the shape of your mouth and throat. Your vocal cords make one buzzy sound (the source), and the tube above them acts like a filter that lets certain pitches ring louder. Those loud bands are called formants, and moving them around is how one buzz becomes every vowel.

press a vowel — same pitch, different shape

source pitch = 130 Hz (≈ C — the same for every vowel)

“ah” formants: F1 = 800 Hz, F2 = 1150 Hz

The buzz never changes pitch — only the two bright bands move. That is the whole trick of speech and singing: one source, a moving filter.

the two formant bumps of “ah”

Each vowel is a different pair of bumps on the same frequency axis. Press the buttons and watch the two peaks slide — that sliding is what your ear reads as “ah” versus “ee”.

For the classroom

Learning goals

The voice follows a source–filter model: the vocal folds are the source (pitch), the vocal tract is the filter (vowel), and they work independently.
Vowels are distinguished by formants — resonant frequency bands (F1, F2) that boost certain harmonics; e.g. 'ah' ≈ 800/1150 Hz, 'ee' ≈ 300/2300 Hz.
A fixed-pitch buzz sounds like different vowels only because the filter changes — the same reason speech and singing can carry both a melody and words at once.

Try this

1.Play all five vowels in turn and have students confirm the pitch never changes (it is fixed at 130 Hz) while the vowel does — then ask what must be changing (the filter/formants).
2.Have students sustain one note and mouth 'ah–eh–ee–oh–oo' silently, feeling their tongue and jaw move; connect each shape to the sliding F1/F2 peaks on the spectrum plot.