This project is situated in the field of second language phonology, which is a discipline situated at the interface of research on Second Language Acquisition, Phonology, Phonetics and Sociolinguistics. When learners acquire the phonology of a second language, they need to build robust phonological representations, which they can use in perception as well as production. This process can be impeded by their native language phonology. Moreover, listening in a second language can be challening in different listening conditions (for instance when there is background noise), or as a result of sociophonetic variation (for instance when speakers have different regional or non-native accents). In this project we will investigate these challenges to second language learning by setting up experiments that aim to reveal which types of phonetic variation and which phonetic features particularly hinder second language perception.