What this means for learners
Mongghul and Kimeru share 21 sounds — roughly 60% of Kimeru's inventory overlaps with Mongghul. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 6 sounds found only in Kimeru represent the greatest pronunciation challenge for Mongghul 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, Mongghul has 14 sounds not used in Kimeru. Native Kimeru speakers learning Mongghul 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.