Sorry about the misplaced and first post about audio noise. It is a DCS-2132L to which I refer here and above.
The first 2132L was a very low serial number, implying early production. It was returned for a replacement. The 2132L replacement resolved the primary audio noise that made audio non-useful. Background noise still exists, but at a fairly low level compared to the problem in the first device. Importantly, the harsh and overwhelming clicking on the first device happened regardless of connection method, i.e. hardwire vs. wireless. The current low-level noise is present only when using wireless, and does not exist on my 942L's. The low-level noise is not present when using a hardwire connection. So this is now a matter of isolating the wireless noise - and I know the wireless-connected 942Ls are part of that equation because when connected, they cause significant interference with multiple devices, including phones.
The errant disabling of the microphone in the first camera is resolved in the replacement camera.
I can confirm the above observation about G.726 compression vs. G.711, except that on both 2132Ls, G.711 introduces so much noise it is not useful.
The 2132L is being used as the primary camera in a flash flood/debris flow monitoring and warning system. Once past the numerous quirks that are going to be present in any device configured for a highly-specific mission-critical application, it is fair to say that camera operation and utility is nothing short of superb.