Acoustic effects of syllable position of English /s/: Is there a “dark” [s]?

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The effect of syllable position on the acoustics of speech sounds has been studied for different consonants. A well-known example is the “light”-“dark” /l/ distinction in English (e.g., [l]eaf vs. fee[ɫ]). Compared to light onset [l], dark coda [ɫ] generally displays more acoustic energy in the lower frequencies. /l/ shares articulatory and historical properties with the fricative /s/. Both /l/ and /s/ are produced with tongue tip and tongue body motion. As onset, Latin /l/ and /s/ generally remain consonants in Romance languages. As coda, Latin /l/ and /s/ can evolve into vowels (Latin “alter” > French “autre”; Latin “stas” > Italian “stai”). However, it is unknown whether syllable position modulates the acoustics of /s/ in a way similar to /l/. We explored English /s/ in /sVC/ and /CVs/ words. Compared to onset /s/, coda /s/ displayed lower peak frequency and less energy from 4 to 14 kHz. Given this reduction of energy over the higher frequencies, coda /s/ can be described as “dark” [s]. Observing similar spectral effects of syllable position with different sounds informs us about the role of the syllable as a unit of speech production. Moreover, historical sound change can drive predictions about present-day sound alternations.