The voiceless uvular fricative is a type of consonantal sound used in some spoken languages.The symbol in the International Phonetic Alphabet that represents this sound is χ , the Greek chi.The sound is represented by x̣ (ex with underdot) in Americanist phonetic notation.It is sometimes transcribed with x (or r , if rhotic) in broad transcription.

The voiceless alveolar fricatives are a type of fricative consonant pronounced with the tip or blade of the tongue against the alveolar ridge (gum line) just behind the teeth. This refers to a class of sounds, not a single sound. There are at least six types with significant perceptual differences: The voiceless alveolar sibilant [s] has a strong hissing sound, as the s in English sink.