Interesting observation for both cameras. There have been numerous complaints about audio white noise static and these were one of the first cameras I bought. There are better models now that eliminate audio noise. My conclusions in testing .. As long as there is actual sound in what you call up on the camera, the background hiss static is minimal almost to point of not noticible. If actual sound becomes dead quiet such as unoccupied room then crackling white noise background is loud and intolerable. The test I used was running a fan near the cameras then listening on app. The fan is clearly heard as well as other sounds etc very clearly. If fan shut off, then it becomes noisy and crackling because actual room sounds are missing.
Conclusion.. There has to be actual sound to process to make audio tolerable. It seems software does not process dead silence in a room very well and fills our app with the noisy audio we all are familiar with .