What this means for learners
Hupa and Salish share 23 sounds — roughly 53% of Salish's inventory overlaps with Hupa. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 20 sounds found only in Salish represent the greatest pronunciation challenge for Hupa 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, Hupa has 19 sounds not used in Salish. Native Salish speakers learning Hupa 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.