What this means for learners
Washkuk and Sentani share 11 sounds — roughly 35% of Sentani's inventory overlaps with Washkuk. 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 Sentani represent the greatest pronunciation challenge for Washkuk 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, Washkuk has 20 sounds not used in Sentani. Native Sentani speakers learning Washkuk 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.