The main goal of the present research project is to explore how and to which extend the way we produce and perceive speech sounds is influenced by orthography (i.e. the spelling of those sounds). We aim to show that speech sound representations differ for consistent sounds (i.e. sounds that can be spelled with only one possible letter) and inconsistent sounds (i.e. sounds that can be spelled in several different ways within a language). We aim to reveal this incidence of orthography on speech processing at the level of perception and production of sounds, words and newly acquired words. Furthermore, we aim to explore how this phonology-orthography interplay develops in people with impairments in orthography acquisition (i.e. dyslexic patients) and impairments in phonology acquisition (i.e. patients with hearing impairments). Finally, we aim at exploring the complex cross-linguistic phonology-orthography relationship in early bilinguals (acquiring two phonological systems before learning orthography), and in late bilinguals acquiring novel sounds and/or words. We aim to show that speech sound perception and production in a novel language is affected by the orthographic code of the native language, and vice versa, thus revealing a complex interplay between languages and their associated phonology and orthography at play during novel language acquisition.