s1 is a central vowel sound.
Like, for example, the sound of ybu in mijykemkarsna. See also galmijykemkarsna, norgalmijykemkarsna, dizmijykemkarsna, rixykemkarsna, crakemkarsna, galkemkarsna, norgalkemkarsna, dizykemkarsna, tebykemkarsna, naltebykemkarsna, karsna, voksna, ra'isna, relkarsna, zunsna.