Larebear
Pulling my weight
Sorry for the noob question but how are you sharing the audio exactly. I'm not following what is going on in your setup.
I mounted an old indoor VGA IP camera inside my garage that has a connection for a mic. I don't use the camera for video. I use it only for the (mic) audio. The mic is mounted outside the garage under the eave near other cameras that don't support audio, including the Huisun mini-ptz.
Blue Iris software would be required for this to work. With BI, I can configure all of the non-audio cameras that are fairly close to the mic to use the audio from the old camera. In other words, the old camera with the mic is sharing its audio with the other cameras so that audio will be included in recordings or viewing live. Here is the setting in BI.