1 pointIt could also just be a bad mic in the camera. These mics are cheap as dirt and sometimes if they get banged around too much or the camera got dropped they can be useless. The camera may still work fine, but the mic element will be toast. Same goes for the speaker if you can call it that. This would apply to any remote camera, not just the Iris cameras. The cheaper they are I think it is more likely the mic and speaker are next to useless or of poor quality/reliability. The $19 Wyze cameras have a mic and speaker which are nothing to write home about. The speaker being much worse than the mic as far as sound quality/intelligibility. I have a bunch of them and the speakers on all are poor, the mic pick up sound is decent for what they are.
1 pointIn all wireless connections you have a certain amount of unwanted signal called "noise," With your cameras the more negative the noise number is, the weaker its wifi signal is. One thing to note is that the numbers you listed are negative not positive. In your case the high static camera and camera B have a better wifi signal than camera A. RSSI, or “Received Signal Strength Indicator,” is a measurement of how well your device can hear a signal from an access point or router. It’s a value that is useful for determining if you have enough signal to get a good wireless connection. As for the static sound issue you are having I don't believe it is wifi related.