What this means for learners
Sesotho and Javanese share 21 sounds — roughly 46% of Javanese's inventory overlaps with Sesotho. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 12 sounds found only in Javanese represent the greatest pronunciation challenge for Sesotho 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, Sesotho has 25 sounds not used in Javanese. Native Javanese speakers learning Sesotho 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.