What this means for learners
ISOKO and Lingala share 19 sounds — roughly 51% of Lingala's inventory overlaps with ISOKO. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 3 sounds found only in Lingala represent the greatest pronunciation challenge for ISOKO 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, ISOKO has 18 sounds not used in Lingala. Native Lingala speakers learning ISOKO 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.