health% sound alert (help)

[Yukka]

Hello, can you please tell me what to add to this addon so there's a sound alert playing when my life goes below 99%?

There's already sounds alerts when my life goes below 50% and 25%, but I need to add an alert for 99% if possible.

Thanks.

local version = "2.4"
-- www.curse.com/addons/wow/low-hp-alert
-- quick and dirty, what else.
-- Author: Fratzi, Puriya (creator)

-- Frame for updating variables after addon load (used for new addon releases)
local name, addon = ...
local f = CreateFrame("Frame")

local function onevent(self, event, arg1, ...)
    if((event == "ADDON_LOADED" and name == arg1)) then
-- Fresh Install, setting globals
        if(LowHPAlert_Options == nil) then
			LowHPAlert_Options = {
				["tankmode"] = false,
				["soundcombatonly"] = false,
				["soundalwaysoff"] = false,
				["showtext"] = true,
				["version"] = version
			}
		elseif(LowHPAlert_Options.version == nil) then
-- Version is below 2.4, adding new rows into tables, clear up deprecated variables
			LowHPAlert_Options.version = "2.4"
			LowHPAlert_Options.showtext = true
			LowHPAlert_Options.cockpit = nil
			DEFAULT_CHAT_FRAME:AddMessage("----------------------------------------------", 1.0, 0.0, 0.0, nil, true)
			DEFAULT_CHAT_FRAME:AddMessage("Low HP Alert updated - new option to turn off all text messages: /lowhpalert text", 1.0, 0.0, 0.0, nil, true)
			DEFAULT_CHAT_FRAME:AddMessage("----------------------------------------------", 1.0, 0.0, 0.0, nil, true)
		elseif(LowHPAlert_Options.version ~= version) then
-- version is below current version, placeholder for future updates
		elseif(LowHPAlert_Options.version == version) then
--  Everything is ok, placeholder
		end
        f:UnregisterAllEvents()
    end
end

f:RegisterEvent("ADDON_LOADED")
f:SetScript("OnEvent", onevent)


local sounds = true
-- sets player HP to OK!
local LastHealth = 0

-- event caller
function LowHPAlert_OnUpdate()
	if (LowHPAlert_Options.soundalwaysoff) then
		sounds = false
	elseif (LowHPAlert_Options.soundcombatonly and not UnitAffectingCombat("player")) then
		sounds = false
	else
		sounds = true
	end
	
	-- some hardcore math
	hp = UnitHealth("player")
	hpPct = hp / UnitHealthMax("player")
	
	if (LowHPAlert_Options.tankmode) then
		LowHPAlert_OnUpdate_tank()
	else
		LowHPAlert_OnUpdate_default()
	end	
end

-- tankmode 0 = warning at 50% and 25%
function LowHPAlert_OnUpdate_default()
    if (hpPct > 0.5) then
    	LastHealth = 0
		return
    elseif (hpPct > 0.25) then
    	if (LastHealth == 0) then
			if (LowHPAlert_Options.showtext) then HealthMessageFrame:AddMessage("", 1, 1, 0, 1, 3) end
			if (sounds) then PlaySoundFile("Interface\\AddOns\\LowHPAlert\\20.mp3", "master") end
		end
    	LastHealth = 1
		return
     -- HP < 25%
    elseif (LastHealth ~= 2) then
    	if (LowHPAlert_Options.showtext) then HealthMessageFrame:AddMessage("", 1, 0, 0, 1, 3) end
		if (sounds) then PlaySoundFile("Interface\\AddOns\\LowHPAlert\\30.mp3", "master") end
	end
	LastHealth = 2
end

-- slash commands
SLASH_LOWHPALERT1 = '/lowhpalert'
local function slashhandler(msg, editbox)
	if msg == 'tankmode' then
		if(LowHPAlert_Options.tankmode) then
			LowHPAlert_Options.tankmode = false
			print("Tankmode OFF!")
		else
			LowHPAlert_Options.tankmode = true
			LowHPAlert_Options.cockpit = false
			print("Tankmode ON!")
		end
	elseif msg == 'combatmode' then
		if(LowHPAlert_Options.soundcombatonly) then
			LowHPAlert_Options.soundcombatonly = false
			print("Alerts always ON!")
		else
			LowHPAlert_Options.soundcombatonly = true
			print("Alertts will be only played in combat!")
		end
	elseif msg == 'sound' then
		if(LowHPAlert_Options.soundalwaysoff) then
			LowHPAlert_Options.soundalwaysoff = false
			print("Sounds ON!")
		else
			LowHPAlert_Options.soundalwaysoff = true
			print("Sounds always OFF!")
		end
	elseif msg == 'text' then
		if(LowHPAlert_Options.showtext) then
			LowHPAlert_Options.showtext = false
			print("Text OFF!")
		else
			LowHPAlert_Options.showtext = true
			print("Text ON!")
		end
	else
		print(" ")
		print("LowHPAlert version " .. version)
		print("-----------------------------")
		print("/lowhpalert tankmode - only alerts at 30% HP")
		print("/lowhpalert combatmode - only play alert sounds in combat")
		print("/lowhpalert sound - turns off all sounds")
		print("/lowhpalert text - turns off all text messages on screen")
	end
end
SlashCmdList["LOWHPALERT"] = slashhandler

function LowHPAlert_OnLoad()
	DEFAULT_CHAT_FRAME:AddMessage("Low HP Alert version " .. version .. " loaded - Options: /lowhpalert", 0.0, 0.8, 0.0, nil, true)
end

[Dridzt]

If you are already using WeakAuras for other things, it's ideal for such small 'concept' addons.

I'd get rid of the addon and just make an aura tbh.