How do get a sound to play when health is very low?

I am making a 3rd Person Shooter game, so I made a health Gui with this script

wait(.1)
while true do
	hp = game.Players.LocalPlayer.Character.Humanoid.Health/100
	script.Parent:TweenSize(UDim2.new(hp,0,1,0),Enum.EasingDirection.Out,Enum.EasingStyle.Quad,0.15)
	wait(.2)
end

So how do I get this sound SoundService.Heartbeat:Play() to play when the player's health is below 25, The sound is only a second long so how do I loop it and play it if the player's health is below 25 and stop after 25

Use the HealthChanged event to do so. Also, try putting it in a different LocalScript

local hum = game.Players.LocalPlayer.Character.Humanoid
local SoundService = game:GetService("SoundService")

hum:GetPropertyChangedSignal("Health"):Connect(function()
      if health <= 25 then
           SoundService.Heartbeat.Looped = true
           SoundService.Heartbeat:Play()
      elseif SoundService.Heartbeat.Playing == true then
           SoundService.Heartbeat:Stop()
end
end)

Yeah so just use this to detect when the players health has changed.

local player = game.Players.LocalPlayer
local character = player:WaitForChild("Character")
local humanoid = character.Humanoid
local SoundPlaying = false

humanoid.HealthChanged:Connect(function(newHealth)
	if newHealth <= 25 and SoundPlaying == false then 
		-- You need to look up how to make a sound play. It's simple so take the time to learn it.
		-- This is a debounce
		SoundPlaying = true

      	elseif SoundPlaying == true and newHealth > 25 then
           	-- Make the sound stop playing. Look up how it's simple to learn. Just do it lol.
		
		-- Undo the debounce
		SoundPlaying = false
	end
end)

You asked how you would track the health and play a sound. I showed you how to track the health. You need to learn how to do a sound by yourself cause it's not too difficult.

er find the players health and then check if the health is > than 25 then idk