What this means for learners
Border Kuna and Bhumij share 14 sounds — roughly 26% of Bhumij's inventory overlaps with Border Kuna. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 40 sounds found only in Bhumij represent the greatest pronunciation challenge for Border Kuna 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, Border Kuna has 10 sounds not used in Bhumij. Native Bhumij speakers learning Border Kuna 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.