Formant

Formants are defined by Gunnar Fant as 'the spectral peaks of the sound spectrum |P(f)|' of the voice. In speech science and phonetics, formant is also used to mean an acoustic resonance of the human vocal tract. It is often measured as an amplitude peak in the frequency spectrum of the sound, using a spectrogram (in the figure) or a spectrum analyzer, though in vowels spoken with a high fundamental frequency, as in a female or child voice, the frequency of the resonance may lie between the widely-spread harmonics and hence no peak is visible. In acoustics, it refers to a peak in the sound envelope and/or to a resonance in sound sources, notably musical instruments, as well as that of sound chambers. Thus it is possible to talk about the formant frequencies of a room, as exploited, for example, by Alvin Lucier in his piece I Am Sitting in a Room.