You only need to define the corresponding radio sounds into the description.ext file:
// description.ext file
class CfgRadio
{
sounds[] = {};
class my_evac_sound
{
name = "";
sound[] = {"evac_request.ogg", db-0, 1.0};
title = "Requesting evacuation chopper.";
};
};
and then use them:
player sideRadio "my_evac_sound";