Formants (F1, F2, F3, F4)
Definition
Resonant frequencies of the vocal tract that shape vowel quality. F1 and F2 together distinguish vowels (for example /i/ has low F1 and high F2, /a/ has high F1).
- Count typically tracked
- F1 through F4
- Primary role
- F1 and F2 distinguish vowel identity
- Example
- /i/ has low F1, high F2; /a/ has high F1
- Visualised as
- Dark bands on a sound spectrogram
Common questions
What do F3 and F4 add beyond what F1 and F2 already show?+
F3 and F4 carry finer detail about vocal tract shape, including features tied to individual speaker characteristics such as lip rounding and pharyngeal configuration, and can help distinguish speakers whose F1/F2 patterns look similar.
How does a spectrogram make formants visible for measurement?+
A spectrogram plots frequency against time with darkness or colour showing energy concentration. Formants appear as dark horizontal bands because the vocal tract resonances concentrate acoustic energy at those frequencies, letting an examiner trace and measure them directly from the image.
Do formant frequencies stay fixed for a given vowel across different speakers?+
No. Absolute formant frequencies shift with vocal tract length, so the same vowel produced by a person with a longer vocal tract sits at lower frequencies than the same vowel from someone with a shorter tract, even though the relative pattern between formants stays recognisable.
Related terms
- FASR
- Forensic Automatic Speaker Recognition. Likelihood-ratio framework using statistical speaker models (GMM, i-vectors, x-vectors).
- Fundamental Frequency (F0)
- Rate of vocal-fold vibration during voiced speech, perceived as pitch. Typical adult male 80 to 180 Hz, adult female 165 to 255...
- Likelihood Ratio (LR)
- The ratio of two conditional probabilities: the probability of the observed evidence given the prosecution's hypothesis (same source), divided by the probability...
- MFCC
- Mel-Frequency Cepstral Coefficients. The dominant acoustic feature set for automatic speaker recognition.
- Source-Filter Model
- Standard model of voice production: the glottal source (vocal-fold vibration) is filtered by the vocal-tract cavity to produce the speech signal.
- Voice Spectrogram (Sonogram)
- Time-frequency plot of speech. Wideband (about 300 Hz analysis bandwidth) shows formants; narrowband (about 45 Hz) shows harmonics.
- Voiceprint
- Lawrence Kersta's 1962 term for the claim that the spectrographic pattern of an individual's speech is unique enough to serve as a...