From Science Magazine:
Have you noticed this?
A curious vocal pattern has crept into the speech of young adult women who speak American English: low, creaky vibrations, also called vocal fry. Pop singers, such as Britney Spears, slip vocal fry into their music as a way to reach low notes and add style. Now, a new study of young women in New York state shows that the same guttural vibration—once considered a speech disorder—has become a language fad.
Vocal fry, or glottalization, is a low, staccato vibration during speech, produced by a slow fluttering of the vocal chords (listen here). Since the 1960s, vocal fry has been recognized as the lowest of the three vocal registers, which also include falsetto and modal—the usual speaking register. Speakers creak differently according to their gender, although whether it is more common in males or females varies among languages. In American English, anecdotal reports suggest that the behavior is much more common in women. (In British English, the pattern is the opposite.) Historically, continual use of vocal fry was classified as part of a voice disorder that was believed to lead to vocal chord damage. However, in recent years, researchers have noted occasional use of the creak in speakers with normal voice quality.