Where does the gamma go?: Acoustics of the non-labialized voiced velar approximant in Tlingit

The acoustic properties of the voiced velar approximant ɰ are poorly characterized, partly from understudy of relevant languages and partly from uncertainty about the sound itself. We investigate this sound in Tlingit, a critically endangered indigenous language of northwestern North America, where ɰ contrasts with labialized w and palatal j in some dialects but not in others where it was lost through sound change (reductive primary split with merge). We use audio recordings of spoken narratives spanning much of the 20th century from speakers with and without ɰ to characterize this sound both dialectally and diachronically. We measure formants (f1–f3) to identify place information, amplitude for oral aperture, and harmonic-to-noise ratio for manner. Existing descriptions and phonological patterns predict that ɰ is an approximant and not a fricative so we compare against known approximants for differences in turbulence and spectral properties. We also compare against labialized sounds including contrastive w for absence of lowered f3 to exclude lip rounding in ɰ. We argue that it is the intersection of these acoustic cues that distinguishes ɰ from similar sounds, but that these cues are unstable so that dialectal sound change arises from misperception in perturbations of their production.