In speech processing, a formant is a resonance in the vocal tract that results in a peak of energy in the speech signal at a particular frequency. Formants are important for distinguishing between different vowel sounds and correspond to high-energy areas of the spectrum of a vowel. ![[Short-time_analysis_18_0.png]] The formants are numbered from lower to higher frequencies as F1, F2, F3, etc. The frequency of the formants uniquely identifies a vowel. In a [[source-filter model]], the vocal tract can be modeled by a [[cascade combination]] of [[second-order all-pole IIR system]], one for each formant.