High Quality Content by WIKIPEDIA articles! The voiced dental non-sibilant fricative is a type of consonantal sound, used in some spoken languages. The symbol in the International Phonetic Alphabet that represents this sound, eth, is ð, and the equivalent X-SAMPA symbol is D. The symbol ð was taken from the Old English letter eth, which could stand for either a voiced or unvoiced interdental fricative. This symbol is also sometimes used to represent the dental approximant, though that is more clearly written with the lowering diacritic, ð?. The dental fricatives are often called "interdental" because they are often produced with the tongue between the upper and lower teeth, and not just against the back of the teeth, as they are with other dental consonants. It is familiar to English speakers as the th sound in then.