Landscape of the Sepik area in PNG, where Yimas is spoken.
The phonological inventory of Yimas is small, even by the standards of Papuan languages, having only 12 consonants and 4 vowels. The phonology exhibits many features typical of Sepik area languages. There are no fricative phonemes; [s] is just an allophonic realization of the voiceless palatal stop /c/. The language distinguishes four places of articulation: bilabial, dental, palatal, and velar, with a corresponding voiceless stop and nasal in each position. There is no voiced/voiceless distinction for stops, the voiced stops being allophonic realizations of the voiceless stops in certain positions, such as following nasals. Unusually for a Papuan language, Yimas has an r/l distinction, but the /l/ is always palatal(ized), i.e., [ly] or [¥], and the /r/ is always dental-alveolar, to a large extent varying freely between [l] and [\] as phonetic realizations.
The vocalic system is typically, one might say prototypically, Sepik. There is a dearth of vowel phonemes, both abstractly and as the segmental phonemes of particular words. Many words lack underlying vowel phonemes altogether, and the string of underlying consonants is broken up in phonetic realization by epenthetic vowels inserted by a phonological rule. The only clear unambiguous underlying vowel in the language is the low central vowel /a/. The three high vowels /i, i, u/ are often the result of vowel epenthesis, the /i/ almost invariably so. The semivowels /y/ and /w/, especially the latter, interact closely with the phonological rules involving vowels, such that their phonetic realization is often the result of these rules. Stress is predictable and generally occurs initially.