What this means for learners
Lahu and Javanese share 23 sounds — roughly 50% of Javanese's inventory overlaps with Lahu. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 10 sounds found only in Javanese represent the greatest pronunciation challenge for Lahu 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, Lahu has 23 sounds not used in Javanese. Native Javanese speakers learning Lahu 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.