Formants are the resonant frequencies of the vocal tract. The first two formants, F1 and F2, determine which vowel you hear.

Why do male and female voices sound different?

Female voices have a higher fundamental frequency and, on average, a shorter vocal tract, which raises the formant frequencies. This tool models both.

How do F2 and lip rounding relate?

F2 encodes both tongue position and lip rounding. Front vowels have a high F2 and back vowels a low F2; rounding the lips also lowers F2. You can tell rounding from backing apart via F3: rounding lowers F3 while backing the tongue raises it.

What does F3 control?

F3 controls retroflex (r-colored) coloring. Lowering F3 makes a vowel sound more retroflex, like the rhotacized 'er' vowel.

Vowel Synthesizer

Shape vowel sounds by tuning the formant frequencies (F1, F2, F3), with an interactive IPA chart and male or female voices.

How it works

Start the sound. Click Play to run the sawtooth oscillator.
Pick a vowel. Click a symbol on the IPA chart, or drag the marker to sweep between vowels.
Choose a voice. Male uses a 120 Hz fundamental, Female uses 220 Hz with higher formants.
Fine-tune. Adjust the F1, F2 and F3 sliders to shape the timbre.

What are formants?

A vowel's sound comes from the resonant frequencies of the vocal tract, called formants. When you speak, the shape of your mouth and tongue turns the buzz from your vocal folds into a particular set of resonant peaks, and it is the pattern of these peaks, especially the first three, that your ear recognizes as a specific vowel.

This tool passes a sawtooth wave (rich in harmonics) through three band-pass filters tuned to F1, F2 and F3, which recreates the vowel timbre you hear when someone speaks.

F1, F2 and F3: three knobs for one vowel

F1 sets vowel height. Open vowels like /a/ have a high F1; close vowels like /i/ and /u/ have a low F1. The more open the jaw, the higher F1.
F2 sets frontness, and it is also lowered by lip rounding. Front vowels like /i/ have a high F2; back vowels like /u/ have a low F2. Rounding the lips lowers F2, which moves a vowel toward the back of the chart even when the tongue stays forward.
F3 sets retroflex coloring. The lower F3, the more retroflex (r-colored) a vowel sounds, like the "er" vowel in English or the rhotacized vowels of Mandarin.

How to tell rounding apart from backing. Both lip rounding and moving the tongue back lower F2, so the two can sound alike on F2 alone. The difference shows up in F3: lip rounding lowers F3, whereas backing the tongue raises F3. That is how the two articulations are told apart acoustically.

Voice type: male, female and child

The fundamental frequency sets the overall voice register: male voices average about 120 Hz, female voices about 220 Hz, and children higher still. Because the vocal tract is also shorter at higher pitches, a higher voice comes with proportionally higher formants, which is why this tool scales F1, F2 and F3 up together when you switch to the female voice.

Frequently asked questions

Is this tool free?

Yes. It is completely free, with no signup and no limit.

Does the sound run in my browser?

Yes. All synthesis happens locally with the Web Audio API; nothing is uploaded or recorded.

Can I hear the difference between male and female voices?

Yes. Switch the Voice control to hear a higher pitch with raised formants (female) versus a lower pitch (male).