After interviewing several "squeal-prone" friends, The Cut's Maureen O'Connor organized squeals into five different categories.
There is, for example, the "Squeal for the Sisterhood." This particular sound expresses "camaraderie, a call-and-response ritual announcing participants’ mutual enthusiasm — and a corollary DGAF attitude toward non-participants." It shouldn't be confused with the "Squeal as Social Lubricant," which is more inclusive, and, as O'Connor writes, is "the vocalized equivalent of buying a round of shots for everyone at the bar." Squeals are just as likely to signal excitement or merriment as they are to indicate secret, barely-suppressed rage.
Squeals, O'Connor points out, contain multitudes.
The whole post, found here, is excellent and certainly worth a read. After all, you may be a grown woman (or man), but nothing can express genuine enthusiasm for an engagement/new baby/promotion quite like a wholehearted squeal. (The Cut)