A new era in the physiological investigation of linguistic sounds was opened up by X-ray photography.
Roman JakobsonSpeech sounds cannot be understood, delimited, classified and explained except in the light of the tasks which they perform in language.
Roman JakobsonLinguistic sounds, considered as external, physical phenomena have two aspects, the motor and the acoustic.
Roman JakobsonIt is once again the vexing problem of identity within variety; without a solution to this disturbing problem there can be no system, no classification.
Roman Jakobson