What this means for learners
Berom and Dioula share 29 sounds — roughly 74% of Dioula's inventory overlaps with Berom. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 10 sounds found only in Dioula represent the greatest pronunciation challenge for Berom speakers. The adult brain tends to map unfamiliar sounds onto the closest native equivalent — a process that produces the characteristic "accent" of a second-language speaker. Learning to hear and produce these sounds as distinct requires focused ear training, not just repetition.
Conversely, Berom has 2 sounds not used in Dioula. Native Dioula speakers learning Berom will face the mirror-image challenge with these sounds.
Phoneme inventories from PHOIBLE. Data reflects one documented inventory per language; some variation exists across dialects and sources.