What this means for learners
Rundi and Bhumij share 15 sounds — roughly 28% of Bhumij's inventory overlaps with Rundi. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 39 sounds found only in Bhumij represent the greatest pronunciation challenge for Rundi 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, Rundi has 14 sounds not used in Bhumij. Native Bhumij speakers learning Rundi 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.