This is probably one of the weirder things on a phone that I’ve personally seen. This morning I finished setting up a brand new, out of the box, LG L322DL on Android 10. Setting up a Google account, check. Got all the updates, check. Then I noticed a sound that I thought was a dial tone coming from the phone.
Tried rebooting it. Still there. It’s a kind of a low beep that changes with the volume going up or down, but even at the maximum volume it is still kind of low. I later realized it is not a dial tone, but sounds exactly like a telephone busy signal.
The beep would remain for a long time and it almost feels like it’s going to stay. But then it would disappear out of the blue for a short while (a few seconds, a few minutes, or until the next reboot) and then come back, without me doing anything. I have done my homework and found some pages where people talk about similar problems, e.g. this and this. I have tried everything suggested on there, including putting the phone in safe mode. Nothing has worked.
Even if something happens and then the busy tone goes away, regardless of whether the two have a causal relationship, on reboot the beep comes back.
The tone disappears from time to time but always comes back later.
The phone is isolated and charged. It has nothing to do with battery, charging, notifications, roaming, or sound effects as far as I can tell.