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

The effect of syllable position on the acoustic structure of speech sounds has been studied for different consonants. A well-known example is the lateral approximant /l/ in American English (AE), whose spectral properties vary between initial and final position, as characterized by the light–dark [l] distinction, as in [l] eaf versus [feeɫ]. Spectral differences between initial and final /l/ have been widely reported, with final [feeɫ] displaying a higher concentration of acoustic energy in the low-frequency range. /l/ shares articulatory properties with the alveolar fricative /s/, and both sounds display similar trajectories of diachronic change at initial versus final position. However, it is unknown whether syllable position modulates the acoustic properties of /s/ in a way similar to that observed for /l/. We explored the AE /s/ in initial and final position using sVC and CVs words with symmetrical contexts. Acoustic parameters were computed from multitaper spectra. Preliminary results show that the amplitude at higher frequencies is less intense in final than initial [s]. Moreover, the frequency of the main spectral peak was lower in final [s]. It appears that similarities between /s/ and /l/ extend to the effect of syllable position on spectral properties.