Mariah's range is about Bb2-G#7 which is 4 octaves and 5 notes. Bb2-Bb3 1 octave, Bb3-Bb4, 2 octaves, Bb4-Bb5 3 octaves, Bb5-Bb6 4 octaves, and then 5 extra notes. Bb2 from a vocal demonstration and G#7 from Emotions live. She has never sang lower than that. She hits C3 in plenty of songs: Emotions, You're So Cold, My All, You And I, and another song which i cant seem to remember. But from what I know, switching from falsetto to belting in chest is considered difficult by other female singers.