The fricatives are consonants produced by passing air through a narrow channel made by placing two articulators close to each other. [ 1 ] These can be the lower lip against the upper teeth , in the case of [f] ; the posterior part of the tongue against the soft palate , in the case of German [x] , the final consonant of Bach ; or the side of the tongue against molars , in the case of [ɬ] Welsh , Lloyd’s initial consonant .
This turbulent flow of air is called friction . A special subgroup of fricatives is wheezing . They are also formed through the passage of air through a narrow channel, however, in addition, the tongue curves so as to conduct air over the tips of the teeth. In Portuguese [s] , [z] , [ʃ] , and [ʒ] are examples of this.
It has already been designated by the terms aspirant and strident , whose use is less frequent. The former can be used as a synonym for “fricative”, or, as for example in the Uralic languages , to refer only to non-wheezing fricatives, while the latter can be used as a synonym for “wheezing”, although some authors include also labiodental and / or uvular in this category.
