Thus F came to be the representative of the unvoiced labiodental spirant instead of that for the bilabial voiced spirant.
bilabial fricative becomes an English labiodental (made with the lower lip pressed against the upper teeth ).
Specifically, it analyzes the production and perception of two English phonemes: the voiced labiodental fricative and the voiced dental fricative.
labiodental ' /r / in adult speech is being revised and augmented at present for possible publication.
At least the first two of these definitely use a labiodental.