In the Intonation, the changes of fundamental Fréquence are perceived like variations height: the higher the frequency is, the higher the perceived height is and conversely. Each Voyelle is characterized by its specific stamp. The stamp is determined by two formants (and more for the former vowels) F ₁ and F ₂. In fact the places of the sound Specter of a sound present greatest accumulations of sound pressure. The F ₁ is correlated with the aperture and the F ₂ with the former position (f2 high), posterior (low F2) of the sound (and f3 with the configuration of the lips for the former vowels).