Sibilant

The aspiration appeared was described both in OP1 and OP2:

PE22/65 (3)

s is not strictly homorganic with the other dentals, but is now whatever its origins (these are various) the normal s, a voiceless ‘blade’ consonant, with the blade of the tongue in contact (and so possessing an i-timbre), but with the point touching the lower teeth. It has no tendency, even before [i] to palatalization to [š] or [ç].