Voiceless postalveolar fricative

A voiceless postalveolar fricative is a type of consonantal sound used in some spoken languages. The International Phonetic Association uses the term voiceless postalveolar fricative only for the sound [ʃ], but it also describes the voiceless postalveolar non-sibilant fricative [ɹ̠̊˔], for which there are significant perceptual differences.