Editing Formant (section)

==Formant estimation==

Formants, whether they are seen as acoustic resonances of the vocal tract, or as local maxima in the speech spectrum, like [[band-pass filter]]s, are defined by their frequency and by their [[spectral width]] ([[Bandwidth (signal processing)|bandwidth]]).

Different methods exist to obtain this information. Formant frequencies, in their acoustic definition, can be estimated from the [[frequency spectrum]] of the sound, using a spectrogram (in the figure) or a spectrum analyzer. However, to estimate the acoustic resonances of the vocal tract (i.e. the speech definition of formants) from a speech recording, one can use ''[[linear predictive coding]]''. An intermediate approach consists in extracting the spectral envelope by neutralizing the fundamental frequency,<ref>{{cite journal |last1=Kawahara |first1=Hideki |last2=Masuda-Katsuse |first2=Ikuyo |last3=de Cheveigné |first3=Alain |title=Restructuring speech representations using a pitch-adaptive time–frequency smoothing and an instantaneous-frequency-based F0 extraction: Possible role of a repetitive structure in sounds |journal=Speech Communication |date=April 1999 |volume=27 |issue=3–4 |pages=187–207 |doi=10.1016/S0167-6393(98)00085-5}}</ref> and only then looking for local maxima in the spectral envelope.