I also do not have Alexa hooked up, so the "solution" is incorrect. After multiple calls to Samsung, while they do not know "why" the two tone notification occurrs, the last person did claim to know how to stop it. Every modern model is susceptible, and finding "where" your precise location of this solution is will vary, but the gist is:
Buried in "settings" somewhere is "sound feedback" and you want to toggle that to "off."
On my model, UN65TU850D, it is:
Settimgs-> All Settings-> Sound-> Expert Settings->scroll to bottom leads you to Sound Feedback, hit enter until you get "off" then back out.
I just did this, and the problem is so random and intermittant, I will not know for who knows how long if this worked, but I figured others could try it, and we would all find out together