Job is talking about the place where people go after they stop living. AT: "In that place, evil people stop causing trouble" (See: [[rc://en/ta/man/translate/figs-explicit]])
Here "voice" is a metonym for the power that the slave drivers have over the slaves. AT: "They are no longer under the control of the slave drivers" (See: [[rc://en/ta/man/translate/figs-metonymy]])