High Quality Content by WIKIPEDIA articles! The voiced alveolar fricatives are consonantal sounds. The symbol in the International Phonetic Alphabet that represents these sounds depends on whether a sibilant or non-sibilant fricative is being described. The symbol for the alveolar sibilant is z, and the equivalent X-SAMPA symbol is z. The IPA symbol [z] is not normally used for dental or postalveolar sibilants unless modified by a diacritic ([z?] and [z?] respectively).