Strident vowels are fairly common in Khoisan languages, where they contrast with simple pharyngealized vowels. Stridency may be a type of phonation called harsh voice. A similar phonation, but without the trill, is called pressed voice or ventricular voice. The Bai language of southern China has a register system with allophonic strident and pressed vowels.
There is no official symbol for stridency in the IPA, though a superscript ⟨ʢ⟩ is often used. In some literature a subscript double tilde (≈) is sometimes used, as seen here on the letter ⟨a⟩ (⟨a᷽⟩):
This has been accepted into Unicode at code point U+1DFD.