What this means for learners
Bobo and Fɔn share 33 sounds — roughly 79% of Fɔn's inventory overlaps with Bobo. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 9 sounds found only in Fɔn represent the greatest pronunciation challenge for Bobo 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, Bobo has 7 sounds not used in Fɔn. Native Fɔn speakers learning Bobo 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.