TTTPrepareRound hook is not working

[CyberAP]

I have this code:

local PrepareSounds = {
"p01.mp3",
"p02.mp3",
"p03.mp3",
"p04.mp3",
"p05.mp3"
}

for k, v in pairs (PrepareSounds) do
	resource.AddFile("sound/"..v)
	util.PrecacheSound("sound/"..v)
end

local function PlayPrepareSound()
	BroadcastLua('surface.PlaySound("'..PrepareSounds[math.random(1, #PrepareSounds)]..'")')
end

hook.Add("TTTPrepareRound", "SoundPrepareRound", PlayPrepareSound)

And it doesn't work. But If I replace TTTPrepareRound with TTTBeginRound it magically works! I suppose it is a TTT code issue.