I'm going to preface this by saying I have almost no experience with electrical projects like this, so if I use the wrong terminology or I'm doing something stupid please bear with me.
I've been trying to hookup an active buzzer to GPIO2 and have the ESP turn it on and off every few seconds as a test. It works fine if I leave GPIO2 un-plugged on boot then plug it in a few seconds later, but if I leave it plugged in at boot I just get a solid tone from the buzzer until I unplug it again.
Looking around I've found sources saying that I need a pull-up resistor as well as sources saying that there is one built in to the board, so I'm not sure what is going on with that. I'm don't really have a solid understanding of how the pull-up resistor helps in this case.
I did try putting a 10k resistor between the 3.3v input and buzzer's positive connection and that also resulted in a solid tone when plugging in the board.
I'm also powering this through the FTDI board that used to program the board, and I don't have a spec sheet for the buzzer. It came in a set of misc electronic parts.