siren={}
for i=1,32 do siren[i]=0 end
function distance(x1,y1,x2,y2)
     return math.floor(math.sqrt(math.pow(x1-x2,2)+math.pow(y1-y2,2)))
end

addhook("say","OnSay")
function OnSay(id,txt)
     if txt=="!siren" then
          if siren[id]==1 then siren[id]=0 else siren[id]=1 end
     end
end

addhook("second","EverySecond")
function EverySecond()
     for _,id in pairs(player(0,"tableliving")) do
          if siren[id]==1 then
               for _,ID in pairs(player(0,"tableliving")) do
                    if distance(player(id,"x"),player(id,"y"),player(ID,"x"),player(ID,"y"))<=500 then
                         parse('sv_sound2 '..ID..' "env/alarm.wav"')
                    end
               end
          end
     end
end