If you have a microphone with 2.5mm audio jack and dont have a mixer which can play the voice streams to speaker, the best way is to try and use ubuntu laptop which can help us with redirecting the microphone audio to laptop speaker OR if you connect an external speaker to 2.5mm audio out jack, it will also be able to play on larger sounds.
For this connect your microphone to laptop audio in, and type below two commands,
$ sudo apt install pavucontrol
$ pactl load-module module-loopback latency_msec=1
Once you start pavucontrol command, you will see the settings window opened as below, where you can control the volume levels, input and output devices etc as required.
To stop the routing of audio from Microphone to Speaker, use below command
$ pactl exit