There's no Vocal Activity Detector block for the ADAU1701/2 so I built one for my application. This one adapts to input levels that vary around nominal, as one might find in use. It works by comparing the instantaneous input sound to its average level, gating the output ON when the former exceeds the latter. The filter and clipper in the average level path are optional but refine its operation a bit. If you omit the filter, replace it with a gain block.
The manual switch demonstrates a way to "freeze" noise floor tracking by feeding the averaged level back upon itself. This point could be instead wired to logic, for example to prevent undesired tracking of inactive inputs. Monitor the circuit's operation with the real time display block, To optimize its performance, test gating operation over the expected input range. Adjust the DC source DC3 to tweak operation at low signal levels, and the filter (or gain block) for high levels. Adjust the clipper threshold for very high levels. Also vary the Hold number in the PeakEnv2 block to adjust the Hang Time.