From Wikipedia:
Carey can cover all the notes from the alto vocal range leading to those of a coloratura soprano,[54] and her vocal trademark is her ability to sing in the whistle register. She has cited Minnie Riperton as the greatest influence on her singing technique, and from a very early age, she would attempt to emulate Riperton's high notes, to increasing degrees of success as her vocal range expanded. According to most sources, she has a five-octave vocal range, though some credit her with as many as eight octaves.[51] In 2003 her voice was voted the greatest in music in MTV and Blender magazine's countdown of the 22 Greatest Voices in Music. Carey said of the poll: "What it really means is voice of the MTV generation. Of course, it's an enormous compliment, but I don't feel that way about myself."[55]
Carey's voice has come under considerable scrutiny from critics who believe that she does not effectively communicate the message of her songs. Rolling Stone magazine said in 1992, "Carey has a remarkable vocal gift, but to date, unfortunately, her singing has been far more impressive than expressive ... at full speed her range is so superhuman that each excessive note erodes the believability of the lyric she is singing."[56] The New York Daily News wrote that Carey's singing "is ultimately what does her in. For Carey, vocalizing is all about the performance, not the emotions that inspired it ... Does having a great voice automatically make you a great singer? Hardly."[54] Some interpreted Carey's decision to utilise what she described as "breathy" vocals in some of her late 1990s and early 2000s work as a sign that her voice had begun to deteriorate, but she has maintained that it "has been here all along".[57] An article in Vibe magazine indicated that Carey's singing style highlights weaknesses in other aspects of her music: "The impressiveness of her voice—as well as her tendency to oversing—make the blandness of her material all the more flagrant".[4]