Does anyone know why this keeps cloning the screengui? and cloning even if ur not within 5 studs?

Using a while loop in chatted even when you don't need to.

local mic = workspace.Mic --some part in workspace
local range = 5 --in studs btw

game.Players.PlayerAdded:Connect(function(player)
	player.CharacterAdded:Connect(function(char)
		player.Chatted:Connect(function(msg)

--You should only have a while loop when you want to run the same code
--You're only doing this once every Chatted event so just lose the while
		
			--Check to see if player isn't dead
			if char.Humanoid.Health > 0 then
			
--Every R6 or R15 character has a HumanoidRootPart. Better than using torso.
				local hrp = char:WaitForChild("HumanoidRootPart")
				
				--Check distance
				if (mic.Position-hrp.Position).magnitude <= range then
					local screengui = Instance.new("ScreenGui")
					screengui.Name = "Announcement"
					 --You don't even need to rename this
					
					screengui.Parent = player.PlayerGui 
					--because you defined the new instance
					
					local textlabel = Instance.new("TextLabel")
					textlabel.Text = msg:lower()
					textlabel.Size = UDim2.new(1,0,1,0)
					textlabel.TextScaled = true
					textlabel.BackgroundTransparency = .8
					textlabel.Parent = screengui
					
					print(player.Name.." is close") 
					--debug print could be at the start of the if-statement
				
					game:GetService("Debris"):AddItem(screengui, 1) 
					--Same thing as before
				end
			end
		end)
	end)
end)

edit: fix format

The one thing this doesn't do is let other player's see it. You can just use a for loop to create one for each player. Should be easy to do for you but let me know if you need help on that.

Let me know if you need more explanation.