共振峰(formant)是用来描述声学共振现象的一种概念，在语音科学及语音学中，描述的是人类声道中的共振情形。常用的量测方法是由频谱分析或声谱图（spectrogram，见右图）中，寻找频谱中的峰值。但假如说话者，用比较高的基频发出元音，例如小孩或女性的声音，则频谱上看起来比较像是宽带状，比较无法看出明显的峰值。在声学中，共振峰是用来描述声源内部的共振，特别是对乐器而言，指的是共鸣箱内的共振。我们也可以讨论室内空气的共振峰频率，例如Alvin Lucier就在他的作品I Am Sitting in a Room中使用了这个概念。

A formant, as used by James Jeans, is a harmonic of a note that is augmented by a resonance. The speech researcher Gunnar Fant defines formants as "the spectral peaks of the sound spectrum |P(f)|". In acoustics generally, a very similar definition is widely used: the Acoustical Society of America defines a formant as: "a range of frequencies [of a complex sound] in which there is an absolute or relative maximum in the sound spectrum". In speech science and phonetics, however, a formant is also sometimes used to mean an acoustic resonance of the human vocal tract. Thus, in phonetics, formant can mean either a resonance or the spectral maximum that the resonance produces. Formants are often measured as amplitude peaks in the frequency spectrum of the sound, using a spectrogram (in the figure) or a spectrum analyzer and, in the case of the voice, this gives an estimate of the vocal tract resonances. In vowels spoken with a high fundamental frequency, as in a female or child voice, however, the frequency of the resonance may lie between the widely spaced harmonics and hence no corresponding peak is visible.