> The only one I can think of is that my gaming PC was being hacked/remotely accessed and someone was speaking out loud or playing an audio file to prank me

Maybe "espeak"? It it is running Linux, that can be quite easily triggered over ssh to make any computer "speak".

We used to have a media station at home, wake-on-lan. One day, I desparately needed to speak to my wife, but she did not pick up her phone. So I ssh-ed into the media station, sudo-apt-get espeak and then piped "echo 'pick up the phone, berkes needs to talk to you'" into espeak. Freaked her out completely, but she did pick up the phone.