RX-7 audio v2: turbo whistle + exhaust from the action-cam library

- Scanned b-action-cam-footage/clipchamp (99GB, 5 videos of the FD):
  extracted audio NAS-side via linuxserver/ffmpeg container (stream-copy),
  scanned 69min return drive per-second for engine tonality + whistle
  prominence (1.5-9kHz peak vs band median)
- New rev loop: 985-993s highway pull — 0.0Hz pitch drift over 8s,
  whistle ~1.7kHz at +33dB, exhaust + turbo captured together (seam 0.001)
- New whistle-only loop: same pull high-passed 1.2kHz — isolated spool
- SoundController: optional per-car Whistle layer that rides boost
  (throttle held at speed): fades in past 25% speed, pitch 0.9->1.35
- ROTARY_SOUND.md updated; three .ogg uploads needed in Studio now

src/client/SoundController.luau

@@ -34,19 +34,26 @@ local player = Players.LocalPlayer
 
 local SoundController = {}
 
-type EngineSounds = { Idle: string, Rev: string }
+type EngineSounds = { Idle: string, Rev: string, Whistle: string? }
 
 -- Default (generic) sounds --------------------------------------------------
 local DEFAULT_SOUNDS: EngineSounds = {
 	Idle = "rbxassetid://80317022777602", -- Roblox Resources engine loop
 	Rev = "rbxassetid://80317022777602", -- same loop until real rev samples exist
+	Whistle = nil, -- most cars have no turbo layer
 }
 local SQUEAL_ID = "rbxassetid://9120399077" -- ProSoundEffects tyre squeal
 
--- Per-car engine sounds. Fill rx7_fc with the owner's real 13B recordings
--- once uploaded (docs/ROTARY_SOUND.md). Cars not listed use DEFAULT_SOUNDS.
+-- Per-car engine sounds. The rx7_fc loops are cut from the owner's REAL FD
+-- footage (docs/ROTARY_SOUND.md): idle + whistle-rich rev + an isolated
+-- >1.2kHz turbo whistle layer that rides boost. Fill the IDs after the
+-- Studio upload of assets/audio/*.ogg.
 local CAR_SOUNDS: { [string]: EngineSounds } = {
-	-- rx7_fc = { Idle = "rbxassetid://<13B_IDLE>", Rev = "rbxassetid://<13B_REV>" },
+	-- rx7_fc = {
+	-- 	Idle = "rbxassetid://<rx7_idle_loop>",
+	-- 	Rev = "rbxassetid://<rx7_rev_loop>",
+	-- 	Whistle = "rbxassetid://<rx7_whistle_loop>",
+	-- },
 }
 
 -- Tunables --------------------------------------------------------------------
@@ -63,6 +70,13 @@ local SLIP_START = 14 -- studs/sec lateral slip where squeal begins
 local SLIP_FULL = 34 -- lateral slip for max squeal volume
 local SQUEAL_MAX_VOLUME = 0.5
 local RESPONSIVENESS = 8 -- volume/pitch smoothing (1/sec)
+-- Turbo whistle layer (cars with Whistle set): rides "boost" = throttle
+-- held at speed. Fades in above BOOST_START speedFrac when on throttle.
+local WHISTLE_MAX_VOLUME = 0.45
+local BOOST_START = 0.25 -- speedFrac where boost can begin
+local BOOST_FULL = 0.8 -- speedFrac of max whistle
+local WHISTLE_PITCH_MIN = 0.9
+local WHISTLE_PITCH_MAX = 1.35
 
 local heartbeatConn: RBXScriptConnection? = nil
 local seatedConn: RBXScriptConnection? = nil
@@ -104,9 +118,16 @@ local function startAudio(seat: VehicleSeat)
 	local idle = makeSound("EngineIdle", engineSet.Idle, ENGINE_BASE_VOLUME, bodyPart)
 	local rev = makeSound("EngineRev", engineSet.Rev, 0, bodyPart)
 	local squeal = makeSound("TyreSqueal", SQUEAL_ID, 0, bodyPart)
+	local whistle: Sound? = nil
+	if engineSet.Whistle then
+		whistle = makeSound("TurboWhistle", engineSet.Whistle, 0, bodyPart)
+	end
 	idle:Play()
 	rev:Play()
 	squeal:Play() -- all loops run constantly; we fade volumes (no start/stop pops)
+	if whistle then
+		whistle:Play()
+	end
 
 	heartbeatConn = RunService.Heartbeat:Connect(function(dt)
 		if not bodyPart.Parent then
@@ -138,6 +159,16 @@ local function startAudio(seat: VehicleSeat)
 		local braking = (seat.ThrottleFloat == 0 and speed > tuning.MaxSpeed * 0.5) and 0.25 or 0
 		local squealTarget = math.max(slipFrac, braking) * SQUEAL_MAX_VOLUME
 		squeal.Volume += (squealTarget - squeal.Volume) * a
+
+		-- Turbo whistle: spools with throttle held at speed ("on boost").
+		if whistle then
+			local boost = math.clamp((speedFrac - BOOST_START) / (BOOST_FULL - BOOST_START), 0, 1)
+				* math.abs(seat.ThrottleFloat)
+			local whistleVolTarget = WHISTLE_MAX_VOLUME * boost
+			local whistlePitchTarget = WHISTLE_PITCH_MIN + (WHISTLE_PITCH_MAX - WHISTLE_PITCH_MIN) * boost
+			whistle.Volume += (whistleVolTarget - whistle.Volume) * a
+			whistle.PlaybackSpeed += (whistlePitchTarget - whistle.PlaybackSpeed) * a
+		end
 	end)
 end