What this means for learners
Ilocano and Ket share 7 sounds — roughly 22% of Ket's inventory overlaps with Ilocano. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 25 sounds found only in Ket represent the greatest pronunciation challenge for Ilocano 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, Ilocano has 18 sounds not used in Ket. Native Ket speakers learning Ilocano 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.