How can I enable and disable walking sounds?

I am trying to enable walking sound when I am not flying. I have a flying script and whenever I fly I want the game to disable walking sound because in mid-air while flying I hear walking sound. How can I enable walking sound while I am not flying and disable while I am flying?

local wDown = false
local sDown = false
local isFlying = false
local speed = 10
local MAX_SPEED = 45
local MIN_SPEED = 0
spawn(function()
	while player.Character.Humanoid.Health > 0 do
		if isFlying then
			local r = 1+(speed/45)
			player.Character:SetPrimaryPartCFrame(CFrame.new(player.Character.PrimaryPart.Position,mouse.Hit.p)*CFrame.Angles(math.pi/r,math.pi,math.pi))
			player.Character.Torso.FlyingVelocity.Velocity = (mouse.Hit.p - player.Character.Torso.Position).unit * speed
			if wDown then
				speed = speed + 5
				if speed > MAX_SPEED then
					speed = MAX_SPEED
				end
			elseif sDown then
				speed = speed - 5
				if speed < MIN_SPEED then
					speed = MIN_SPEED
				end
			end
		end
		
		game:GetService("RunService").RenderStepped:wait()
	end
end)