What this means for learners
Maasai and Kimeru share 22 sounds — roughly 51% of Kimeru's inventory overlaps with Maasai. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 5 sounds found only in Kimeru represent the greatest pronunciation challenge for Maasai 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, Maasai has 21 sounds not used in Kimeru. Native Kimeru speakers learning Maasai 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.