if I remember correctly, the sound nin only use a cursed seal of level 2, and using that they still lost to the genin, (except for the three that the sand trio helped beat, but they were still beaten by genin). They would probably be chuunin level though, because they used their curse seal to beat jounins that they outnumbered, so they are probably not jounin level, and they seem to be past genin because orochimaru favor them a lot.

Then when you think about it, do the sound ninja have ranks at all?