page_title: Formant
section_title: Formant plots
hierarchical_section_title: Formant / Formant plots
caption_attribution_description: English: Empty Formant plot showing layout of axes
context_page_description: In speech science and phonetics, a formant is the broad spectral maximum that results from an acoustic resonance of the human vocal tract. In acoustics, a formant is usually defined as a broad peak, or local maximum, in the spectrum. For harmonic sounds, with this definition, the formant frequency is sometimes taken as that of the harmonic partial that is most augmented by a resonance. The difference between these two definitions resides in whether "formants" characterise the production mechanisms of a sound or the produced sound itself. In practice, the frequency of a spectral peak differs from the associated resonance frequency, except when, by luck, harmonics are aligned with the resonance frequency.
  A room can be said to have formants characteristic of that particular room, due to the way sound reflects from its walls and objects. Room formants of this nature reinforce themselves by emphasizing specific frequencies and absorbing others, as exploited, for example, by Alvin Lucier in his piece I Am Sitting in a Room.
context_section_description: The first two formants are important in determining the quality of vowels, and are frequently said to correspond to the open/close and front/back dimensions (which have traditionally, though not entirely accurately, been associated with the shape and position of the tongue). Thus the first formant F₁ has a higher frequency for an open vowel (such as [a]) and a lower frequency for a close vowel (such as [i] or [u]); and the second formant F₂ has a higher frequency for a front vowel (such as [i]) and a lower frequency for a back vowel (such as [u]). as can be seen in Fig. 1. 
   Vowels will almost always have four or more distinguishable formants; sometimes there are more than six. However, the first two formants are most important in determining vowel quality, and this is often displayed in terms of a plot of the first formant against the second formant, though this is not sufficient to capture some aspects of vowel quality, such as rounding. An example of how the vowels of a language or dialect may be plotted on a traditional auditory vowel chart and also on a formant plot may be seen in the case of Norwegian.
  Many writers have addressed the problem of finding an optimal alignment of the positions of vowels on formant plots with those on the conventional vowel quadrilateral. The pioneering work of Ladefoged used the Mel scale because this scale was claimed to correspond more closely to the auditory scale of pitch than to the acoustic measure of fundamental frequency expressed in Hertz as in Fig. 1. Two alternatives to the Mel scale are the Bark scale and the ERB-rate scale. A comparison of these three scales is shown by Hayward, p. 141, and formant plots based on the Hertz scale and on the Bark scale are compared on p. 153. Another strategy for improving formant plots that has been widely adopted is to plot on the horizontal axis not the value of F2 but the difference between F1 and F2 for a given vowel.
caption: Fig. 1 Schematic diagram of formant plot
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