I have a camera/light outside and a stick up cam indoors with seemingly no trouble at all.
However tonight the siren went off twice on the outside camera for no reason and I was wondering why.
I was able to turn it off but can see no reason why it was activated.
Hi @KatieJ1. The siren on your Camera would only go off if it was manually activated in the Ring App. Do you have any Shared Users who may have accidentally activated the siren while in the Ring App? If not, I’d suggest resetting your Camera by holding down the setup button for at least 20 seconds. From there, walk it through a fresh setup in the Ring App and keep an eye to make sure the siren is only triggering when you activate it in the Ring App. Let me know if that works out. 
I have a similar problem.
Last night about 8:50pm, our 3 ring camera sirens went off. We could not figure out how turn them off. The Ring app would turn them off for 3 seconds and they would come back on. Finally I unplugged and plugged them in and that worked. Ring shows no event history. I called tech support this morning, their answer: there must have been a glitch in the system and unplugging them was the right answer. Great so if we are not home what do we do!!