What this means for learners
Ga and Fɔn share 27 sounds — roughly 57% of Fɔn's inventory overlaps with Ga. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 15 sounds found only in Fɔn represent the greatest pronunciation challenge for Ga 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, Ga has 20 sounds not used in Fɔn. Native Fɔn speakers learning Ga 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.