sound fixed

This commit is contained in:
2026-05-05 16:10:06 +02:00
parent 547e8706f1
commit 608dabff12
3 changed files with 281 additions and 164 deletions

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@@ -0,0 +1,170 @@
using System;
namespace FluidSim.Core
{
public class OutdoorExhaustReverb
{
// ---- Geometry ----
private const float GroundReflDelay = 0.008f; // 8 ms (≈1.3 m)
private const float WallRefl1Delay = 0.045f; // ≈15 m
private const float WallRefl2Delay = 0.080f; // ≈27 m
private DelayLine groundRefl;
private DelayLine wallRefl1;
private DelayLine wallRefl2;
// ---- FDN for late diffuse tail ----
private const int FDN_CHANNELS = 8; // dense, realistic
private DelayLine[] fdnDelays;
private float[] fdnState;
private OrthonormalMixer mixer; // energypreserving mixing
private LowPassFilter[] channelFilters; // perchannel air absorption
public float DryMix { get; set; } = 1.0f;
public float EarlyMix { get; set; } = 0.5f;
public float TailMix { get; set; } = 0.9f;
public float Feedback { get; set; } = 0.75f; // safe range 0.70.9
public float DampingFreq { get; set; } = 6000f; // Hz, above which air absorbs strongly
public float MatrixCoeff { get; set; } = 0.5f; // (kept for compatibility, not used)
public OutdoorExhaustReverb(int sampleRate)
{
// Early reflection lines
groundRefl = new DelayLine((int)(sampleRate * GroundReflDelay));
wallRefl1 = new DelayLine((int)(sampleRate * WallRefl1Delay));
wallRefl2 = new DelayLine((int)(sampleRate * WallRefl2Delay));
// FDN delays: prime numbers for dense modal density (70150 ms)
int[] baseLengths = { 3203, 4027, 5521, 7027, 8521, 10007, 11503, 13009 };
fdnDelays = new DelayLine[FDN_CHANNELS];
for (int i = 0; i < FDN_CHANNELS; i++)
{
int len = Math.Min(baseLengths[i], (int)(sampleRate * 0.25)); // max 250 ms
fdnDelays[i] = new DelayLine(len);
}
fdnState = new float[FDN_CHANNELS];
mixer = new OrthonormalMixer(FDN_CHANNELS);
// Air absorption: a gentle firstorder lowpass per channel
channelFilters = new LowPassFilter[FDN_CHANNELS];
float initialCutoff = DampingFreq;
for (int i = 0; i < FDN_CHANNELS; i++)
channelFilters[i] = new LowPassFilter(sampleRate, initialCutoff);
}
public float Process(float drySample)
{
// ---- Early reflections ----
float g = groundRefl.ReadWrite(drySample * 0.8f);
float w1 = wallRefl1.ReadWrite(drySample * 0.5f);
float w2 = wallRefl2.ReadWrite(drySample * 0.4f);
float early = (g + w1 + w2) * EarlyMix;
// ---- FDN diffuse tail ----
// Read the delayed outputs (which were stored last iteration)
float[] delOut = new float[FDN_CHANNELS];
for (int i = 0; i < FDN_CHANNELS; i++)
delOut[i] = fdnDelays[i].Read();
// Mix the delayed outputs with the orthonormal matrix -> scattered signals
mixer.Process(delOut, fdnState); // result written into fdnState
// Add fresh input to all channels
for (int i = 0; i < FDN_CHANNELS; i++)
fdnState[i] = drySample * 0.15f + Feedback * fdnState[i];
// Air absorption: perchannel onepole lowpass
for (int i = 0; i < FDN_CHANNELS; i++)
fdnState[i] = channelFilters[i].Process(fdnState[i]);
// Write the new states into the delay lines
for (int i = 0; i < FDN_CHANNELS; i++)
fdnDelays[i].Write(fdnState[i]);
// The tail output is the sum of the delayed outputs *before* the loop
float tailSum = 0f;
for (int i = 0; i < FDN_CHANNELS; i++)
tailSum += delOut[i];
float tail = tailSum * TailMix;
// Final mix
return drySample * DryMix + early + tail;
}
// ---------- Helper classes (same as before but with separate Read/Write) ----------
private class DelayLine
{
private float[] buffer;
private int writePos;
public DelayLine(int length)
{
buffer = new float[Math.Max(length, 1)];
writePos = 0;
}
// Separated Read/Write to avoid ringing with immediate feedback
public float Read()
{
return buffer[writePos];
}
public void Write(float value)
{
buffer[writePos] = value;
writePos = (writePos + 1) % buffer.Length;
}
// Old combined method (not used in FDN, only for early reflections)
public float ReadWrite(float value)
{
float outVal = buffer[writePos];
buffer[writePos] = value;
writePos = (writePos + 1) % buffer.Length;
return outVal;
}
}
private class LowPassFilter
{
private float b0, a1;
private float y1;
private float sampleRate;
public LowPassFilter(int sampleRate, float cutoff)
{
this.sampleRate = sampleRate;
SetCutoff(cutoff);
}
public void SetCutoff(float cutoff)
{
float w = 2 * (float)Math.PI * cutoff / sampleRate;
float a0 = 1 + w;
b0 = w / a0;
a1 = (1 - w) / a0; // firstorder lowpass
}
public float Process(float x)
{
float y = b0 * x - a1 * y1;
y1 = y;
return y;
}
}
/// <summary>
/// Computes a fast orthonormal mixing matrix (like Hadamard, but energypreserving).
/// </summary>
private class OrthonormalMixer
{
private int size;
public OrthonormalMixer(int size) { this.size = size; }
public void Process(float[] input, float[] output)
{
// Simple energyconserving “allpass” mixing:
// Use a Householder reflection: y = (2/n) * sum(x) * ones - x
float sum = 0;
for (int i = 0; i < size; i++) sum += input[i];
float factor = 2.0f / size;
for (int i = 0; i < size; i++)
output[i] = factor * sum - input[i];
}
}
}
}

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@@ -1,132 +1,48 @@
using System;
using FluidSim.Interfaces;
namespace FluidSim.Core
{
public class SoundProcessor
{
private double dt;
private double pipeArea;
private double ambientPressure = 101325.0;
private readonly double dt;
private readonly double scaleFactor; // 1 / (4π r) and a user gain
private double prevMassFlowOut;
// Monopole source state
private double lastMassFlow = 0.0;
// Simple lowpass for derivative smoothing (≈ 23 ms)
private double smoothDMdt;
private readonly double alpha;
// Gains
private float masterGain = 0.0005f;
private float pressureGain = 0.12f;
private float turbulenceGain = 0.05f;
private float turbulence = 0.05f;
public float Gain { get; set; } = 1.0f;
private PinkNoiseGenerator pinkNoise;
// Reverb (outdoor)
private float[] delayLine;
private int writeIndex;
private float feedback = 0.50f;
private float lowpassCoeff = 0.70f;
private float lastFeedbackSample = 0f;
public SoundProcessor(int sampleRate, double pipeDiameterMeters, float reverbTimeMs = 200.0f)
public SoundProcessor(int sampleRate, double listenerDistanceMeters = 1.0)
{
dt = 1.0 / sampleRate;
pipeArea = Math.PI * Math.Pow(pipeDiameterMeters / 2.0, 2.0);
scaleFactor = 1.0 / (4.0 * Math.PI * listenerDistanceMeters);
int delaySamples = (int)(sampleRate * reverbTimeMs / 1000.0);
delayLine = new float[delaySamples];
writeIndex = 0;
pinkNoise = new PinkNoiseGenerator();
// Smoothing time constant ~ 2 ms, blocks singlesample spikes
double tau = 0.002;
alpha = Math.Exp(-dt / tau);
}
public float MasterGain
public float Process(Port port)
{
get => masterGain;
set => masterGain = value;
}
public float PressureGain
{
get => pressureGain;
set => pressureGain = value;
}
public float TurbulenceGain
{
get => turbulenceGain;
set => turbulenceGain = value;
}
public float Turbulence
{
get => turbulence;
set => turbulence = value;
}
// Outflow mass flow (positive = leaving pipe)
double flowOut = -port.MassFlowRate;
public void SetAmbientPressure(double p) => ambientPressure = p;
public void SetPipeDiameter(double diameterMeters) =>
pipeArea = Math.PI * Math.Pow(diameterMeters / 2.0, 2.0);
// Derivative
double rawDerivative = (flowOut - prevMassFlowOut) / dt;
prevMassFlowOut = flowOut;
public float Process(float massFlow, float pipeEndPressure)
{
// 1. Monopole: d(mdot)/dt
double derivative = (massFlow - lastMassFlow) / dt;
lastMassFlow = massFlow;
float monopole = (float)(derivative * masterGain);
// Smooth the derivative to kill isolated spikes
smoothDMdt = alpha * smoothDMdt + (1.0 - alpha) * rawDerivative;
// 2. Pressure component
float pressureDiff = (float)((pipeEndPressure - ambientPressure) / ambientPressure) * pressureGain;
// Farfield monopole pressure
double pressure = smoothDMdt * scaleFactor * Gain;
float mixed = monopole + pressureDiff;
// 3. Turbulence: amplitude ∝ U^8
double velocity = massFlow / (pipeArea * 1.225);
double turbulenceAmp = Math.Pow(Math.Abs(velocity) * turbulence, 3.0);
float pink = pinkNoise.Next() * turbulenceGain * (float)turbulenceAmp;
float combined = mixed + pink;
// 4. Outdoor reverb
float delayed = delayLine[writeIndex];
float filteredDelay = delayed * lowpassCoeff + lastFeedbackSample * (1f - lowpassCoeff);
lastFeedbackSample = filteredDelay;
float wet = delayed + filteredDelay * feedback;
delayLine[writeIndex] = combined + filteredDelay * feedback;
writeIndex = (writeIndex + 1) % delayLine.Length;
// 5. Dry/wet mix
float output = combined * 0.7f + wet * 0.3f;
return MathF.Tanh(output);
}
}
// PinkNoiseGenerator unchanged, same as before
internal class PinkNoiseGenerator
{
private readonly Random random = new Random();
private readonly float[] whiteNoise = new float[7];
private int currentIndex = 0;
public PinkNoiseGenerator()
{
for (int i = 0; i < 7; i++)
whiteNoise[i] = (float)(random.NextDouble() * 2.0 - 1.0);
}
public float Next()
{
whiteNoise[0] = (float)(random.NextDouble() * 2.0 - 1.0);
currentIndex = (currentIndex + 1) & 0x7F;
int updateMask = 0;
int temp = currentIndex;
for (int i = 0; i < 7; i++)
{
if ((temp & 1) == 0)
updateMask |= (1 << i);
temp >>= 1;
}
for (int i = 1; i < 7; i++)
if ((updateMask & (1 << i)) != 0)
whiteNoise[i] = (float)(random.NextDouble() * 2.0 - 1.0);
float sum = 0f;
for (int i = 0; i < 7; i++) sum += whiteNoise[i];
return sum / 3.5f;
// Soft clip to ±1 for audio output (safe limit)
float sample = (float)Math.Tanh(pressure);
return sample;
}
}
}

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@@ -1,5 +1,7 @@
using System;
using FluidSim.Components;
using FluidSim.Utils;
using FluidSim.Interfaces;
using SFML.Graphics;
using SFML.System;
@@ -13,108 +15,137 @@ namespace FluidSim.Core
private Pipe1D exhaustPipe;
private PipeVolumeConnection coupling;
private SoundProcessor soundProcessor;
private OutdoorExhaustReverb reverb;
private Port exitPort = new Port();
private double dt;
private double ambientPressure = 101325.0;
private double pipeArea;
private const double AmbientPressure = 101325.0;
private double time;
private int stepCount = 0;
private const int LogInterval = 10000;
// Throttle 0..1 → target combustion pressure
public double Throttle { get; set; } = 0.05; // tiny throttle to keep idle
private const double IdlePeakPressure = 5.0 * 101325.0; // 5 bar
private const double MaxPeakPressure = 50.0 * 101325.0; // 50 bar
// Throttle 0..1
public double Throttle { get; set; } = 0.0; // start with a light idle throttle
// ---- Realistic combustion parameters ----
private const double FullLoadPeakPressure = 70.0 * 101325.0; // 15 bar
// ---- Idle speed governor ----
private const double TargetIdleRPM = 800.0; // rad/s = RPM * π/30, we'll convert
public override void Initialize(int sampleRate)
{
dt = 1.0 / sampleRate;
// Crankshaft (inertia + friction)
crankshaft = new Crankshaft(initialRPM: 100.0) // starter speed
// ---- Crankshaft: inertia + friction that gives ~800 RPM at idle ----
crankshaft = new Crankshaft(initialRPM: 600.0) // start a bit low
{
Inertia = 0.05,
FrictionConstant = 1.0,
FrictionViscous = 0.01
Inertia = 0.005, // slightly heavier flywheel
FrictionConstant = 0.8, // static friction
FrictionViscous = 0.01 // viscous (linear with RPM)
};
// Pipe
double pipeLength = 0.5;
// ---- Pipe: add a tiny bit of damping to prevent unrealistic shocks ----
double pipeLength = 2;
double pipeRadius = 0.1;
double pipeArea = Math.PI * pipeRadius * pipeRadius;
pipeArea = Math.PI * pipeRadius * pipeRadius;
exhaustPipe = new Pipe1D(pipeLength, pipeArea, sampleRate, forcedCellCount: 60);
exhaustPipe.SetUniformState(1.225, 0.0, ambientPressure);
exhaustPipe.EnergyRelaxationRate = 0f;
exhaustPipe.DampingMultiplier = 0;
exhaustPipe.SetUniformState(1.225, 0.0, AmbientPressure);
exhaustPipe.DampingMultiplier = 5;
exhaustPipe.EnergyRelaxationRate = 50;
// Cylinder (coupled to crankshaft)
// ---- Cylinder ----
engineCyl = new EngineCylinder(crankshaft,
bore: 0.065, stroke: 0.0565, compressionRatio: 10.0,
pipeArea: pipeArea, sampleRate: sampleRate);
// Coupling (valve → pipe)
// ---- Coupling ----
coupling = new PipeVolumeConnection(engineCyl.Cylinder, exhaustPipe, true, orificeArea: 0.0);
// Solver
// ---- Solver ----
solver = new Solver();
solver.SetTimeStep(dt);
solver.AddVolume(engineCyl.Cylinder);
solver.AddPipe(exhaustPipe);
solver.AddConnection(coupling);
solver.SetPipeBoundary(exhaustPipe, false, BoundaryType.OpenEnd, ambientPressure);
solver.SetPipeBoundary(exhaustPipe, false, BoundaryType.OpenEnd, AmbientPressure);
// Sound (your tuned gains)
soundProcessor = new SoundProcessor(sampleRate, pipeRadius * 2, reverbTimeMs: 500.0f);
soundProcessor.MasterGain = 0.0f; //0.00001f;
soundProcessor.PressureGain = 0.1f;
soundProcessor.TurbulenceGain = 0.0f;
soundProcessor.Turbulence = 0.001f;
soundProcessor.SetAmbientPressure(ambientPressure);
// ---- Sound processor (stable version) ----
soundProcessor = new SoundProcessor(sampleRate, pipeRadius * 2);
soundProcessor.Gain = 0.00001f;
Console.WriteLine("=== EngineScenario (torquedriven RPM, throttle = pressure) ===");
Console.WriteLine($"Crankshaft inertia: {crankshaft.Inertia}, friction: {crankshaft.FrictionConstant} + {crankshaft.FrictionViscous}*ω");
Console.WriteLine($"Throttle range: {IdlePeakPressure/101325:F0} {MaxPeakPressure/101325:F0} bar");
// ---- Reverb ----
reverb = new OutdoorExhaustReverb(sampleRate);
// Church: vast, highly reflective, bright
reverb.DryMix = 1.0f; // always full dry signal
reverb.EarlyMix = 0.5f; // distinct early reflections from distant walls
reverb.TailMix = 0.9f; // huge tail, almost as loud as the dry sound
reverb.Feedback = 0.9f; // long decay roughly 3s reverb time (with current delay lengths)
reverb.DampingFreq = 6000f; // bright: highfrequency energy stays for a long time
reverb.MatrixCoeff = 0.5f; // default orthogonal mix
Console.WriteLine("=== EngineScenario (Stable) ===");
Console.WriteLine($"Crankshaft inertia: {crankshaft.Inertia}");
Console.WriteLine($"Pipe: {pipeLength} m, fundamental: {340/(4*pipeLength):F1} Hz");
}
public override float Process()
{
// 1. Map throttle to target peak pressure
double targetPressure = IdlePeakPressure + Throttle * (MaxPeakPressure - IdlePeakPressure);
// ---- RPM governor: adjust throttle to maintain idle when no user input ----
double currentRPM = crankshaft.AngularVelocity * 60.0 / (2.0 * Math.PI);
double throttle = Math.Clamp(Throttle, 0.05, 1.0); // never let it drop below a tiny value
// ---- Target combustion pressure ----
double targetPressure = throttle * FullLoadPeakPressure;
engineCyl.TargetPeakPressure = targetPressure;
// 2. Step the cylinder (adds torque to crankshaft, updates valve)
// ---- Simulate one timestep ----
engineCyl.Step(dt);
// 3. Integrate crankshaft (applies friction, updates RPM)
crankshaft.Step(dt);
// 4. Set orifice area for coupling
coupling.OrificeArea = engineCyl.OrificeArea;
solver.Step();
// 5. Fluid solver step
float massFlow = solver.Step();
float endPressure = (float)exhaustPipe.GetCellPressure(exhaustPipe.GetCellCount() - 1);
// ---- Update exit port with safety clamps ----
UpdateExitPort();
// 6. Audio
float audioSample = soundProcessor.Process(massFlow, endPressure);
// ---- Generate audio ----
float dry = soundProcessor.Process(exitPort);
float wet = reverb.Process(dry);
time += dt;
stepCount++;
if (stepCount % LogInterval == 0) {
Console.WriteLine(audioSample);
}
if (stepCount % 1000 == 0 && false)
{
Console.WriteLine($"{time,5:F3} {crankshaft.AngularVelocity*60/(2*Math.PI),5:F0} RPM " +
$"Thr:{Throttle:F2} P_target:{targetPressure/101325:F1} bar " +
$"mflow:{massFlow,14:E4} Comb#{engineCyl.CombustionCount} Mis#{engineCyl.MisfireCount}");
}
return audioSample;
return wet;
}
private void UpdateExitPort()
{
int last = exhaustPipe.GetCellCount() - 1;
double p = exhaustPipe.GetCellPressure(last);
double rho = exhaustPipe.GetCellDensity(last);
double vel = exhaustPipe.GetCellVelocity(last);
// Clamp density to physically possible values
if (rho < 0.01) rho = 0.01; // never let it approach zero
if (rho > 50.0) rho = 50.0; // never let it become absurd
// Clamp velocity to ± 500 m/s (safe subsonic)
vel = Math.Clamp(vel, -500.0, 500.0);
double outflowMassFlow = rho * vel * pipeArea;
// Clamp exit pressure to sensible range (0.1 20 bar)
p = Math.Clamp(p, 1e4, 2e6);
exitPort.Pressure = p;
exitPort.Density = rho;
exitPort.Temperature = p / (rho * 287.05);
exitPort.MassFlowRate = -outflowMassFlow;
exitPort.SpecificEnthalpy = 0.0;
}
// ---- Drawing (unchanged) ----
public override void Draw(RenderWindow target)
{
float winW = target.GetView().Size.X;