Just to give you a little fill-in.... when the 200 first came out quite a few people had a distinct hum, noticeable from across the room. Other people did not have the hum at all, so if you had it, you were a complainer.
At first Uniden denied it but the YouTube videos we're pretty convincing. Also radios were being returned. They approached the problem two ways.
A mitigation device was given out free to anyone who asked for it and a video was made by Paul to show how to install it. It did reduce the hum but results were mixed and people ended up bending it a little or adding copper tape to it but for many the hum continued, albeit greatly reduced.
There was also those folks who reported no hum at all.
The mitigation device is now installed in the factory. in addition to the mitigation device there was also a firmware update with the audio off option you're speaking of, again results were mixed.
There was a thread where a lot of brainstorming went into finding the source of this grounding problem and fixing it. A member named static discharge did come up with a permanent fix for the problem but it does take some disassembly of the radio.
As we know because of the virus there was a shortage of the SDS radios and they were back ordered for a while, no one had them in stock. Bearcat Warehouse did get a load in and I picked up a second sds200 last week. It has absolutely no hum. I have an external speaker plugged into the back and if I press my ear to the speaker I do here that familiar sound but I have to concentrate to hear it and the minute I move my ear from the speaker I don't hear it, so I have no use for the audio off option.
If you're not getting any clipping of transmissions and it silences the radio until the squelch is broken then that's how it should work.