Back to Home

Vowel Space

A real-time vowel chart: speak or sing, and your first two formants are traced on the F1–F2 plane as you go.

Educational and biofeedback tool. The live formant track is not a validated clinical measure.

About this tool

Reading the chart

The horizontal axis is the second formant F2 (front vowels on the left), and the vertical axis is the first formant F1 (close vowels at the top), as in a phonetician's vowel chart. Before calibration the axes show your formants in Hz, scaled by the voice type. After calibration they show normalized values: your vowels are mapped onto an adult-male reference space, so you can compare yourself with the reference vowels.

Calibration

Your “ee”, “ah” and “oo” (each measured from the spectrum averaged over the hold) define a mapping, affine in log-frequency, from your vowel space onto the corner vowels [i], [a], [u] of the selected language, so your corner vowels land exactly on that language's. If [u] cannot be measured, [i] and [a] alone scale each axis separately. Working in log-frequency matches the main source of speaker differences: vocal-tract length scales all formants by roughly the same factor. The calibration is remembered in this browser.

How formants are tracked

The microphone signal is low-pass filtered and resampled to 11 kHz. In each 30 ms window a 14th-order LPC fit gives resonance candidates, and an autocorrelation test checks that the window is voiced. A tracker picks F1 and F2 by sharpness, rank and continuity, rejects pairs outside the vowel space, and accepts a sudden jump only when several consecutive frames agree. The background noise spectrum is learned during pauses; a resonance that does not rise clearly above it is not accepted as a formant, so a voice that is too soft shows a gap rather than a wrong point.

Close back vowels

Close back vowels such as [u] and [o] get a second analysis: their F1 and F2 lie close together and F2 is often 20–25 dB weaker than F1, so a full-band fit tends to merge them. When the spectrum has little energy where front vowels have their F2, the signal is low-pass filtered to 1.7 kHz, F1 is located and filtered out, and F2 is sought in what remains.

Reference vowels

Reference vowels are average F1 and F2 of adult male speakers (the chart's reference scale), from:

  • Peterson, G. E., & Barney, H. L. (1952). Control methods used in a study of the vowels. J. Acoust. Soc. Am. 24, 175–184. doi:10.1121/1.1906875
  • Hillenbrand, J. M., Getty, L. A., Clark, M. J., & Wheeler, K. (1995). Acoustic characteristics of American English vowels. J. Acoust. Soc. Am. 97, 3099–3111. doi:10.1121/1.411872
  • Escudero, P., Boersma, P., Rauber, A. S., & Bion, R. A. H. (2009). A cross-dialect acoustic description of vowels: Brazilian and European Portuguese. J. Acoust. Soc. Am. 126, 1379–1393. doi:10.1121/1.3180321
  • Chládková, K., Escudero, P., & Boersma, P. (2011). Context-specific acoustic differences between Peruvian and Iberian Spanish vowels. J. Acoust. Soc. Am. 130, 416–428. doi:10.1121/1.3592242

Real speakers vary a lot, and dialects differ: treat the circles as neighbourhoods, not exact targets. High voices (above about 250 Hz) make formants hard to measure for any method, because the harmonics sample the spectrum too sparsely. In the Generic set, [ə] is the neutral uniform tube.

Recording and privacy

Recording keeps your voice and the tracked values (about 60 per second) in your browser. Replay plays the audio while the trace redraws in step with it. The WAV (mono, 16-bit, at the microphone's sample rate) can be opened in Praat; the CSV has time, voicing, f0, raw F1 and F2 in Hz, and the F1 and F2 shown on the chart.

Everything runs in your browser: your voice and recordings are never uploaded.