There should be some way to disable these audio notifications. I have not been able to find a way to disable this, and it seems like a hot issue on the Amazon forum as well.
I’m not aware of a way to disable this.
However, from Amazon’s vantage point, this may be a security feature – if you had a phone call come in that you wanted to be private, it would be nice to be reminded that your whole house could hear your phone call before you answered!
Hopefully it’s something Amazon addresses in the future!