Update FFT demo to show FFT with Hann window

dev/old/18-09-19_microphone_FFT_revisited/ScottPlotMicrophoneFFT/ScottPlotMicrophoneFFT/Form1.cs

@@ -10,6 +10,7 @@
 
 using NAudio.Wave;
 using NAudio.CoreAudioApi;
+using ScottPlot;
 
 namespace ScottPlotMicrophoneFFT
 {
@@ -19,6 +20,7 @@ public partial class Form1 : Form
  // MICROPHONE ANALYSIS SETTINGS
  private int RATE = 44100; // sample rate of the sound card
  private int BUFFERSIZE = (int)Math.Pow(2, 11); // must be a multiple of 2
+ double[] hannWindow;
 
  // prepare class objects
  public BufferedWaveProvider bwp;
@@ -29,6 +31,17 @@ public Form1()
  SetupGraphLabels();
  StartListeningToMicrophone();
  timerReplot.Enabled = true;
+ GenerateHannWindow();
+ }
+
+ private void GenerateHannWindow()
+ {
+ hannWindow = new double[BUFFERSIZE/2];
+ var angleUnit = 2 * Math.PI / (hannWindow.Length - 1);
+ for (int i = 0; i < hannWindow.Length; i++)
+ {
+ hannWindow[i] = 0.5*(1-Math.Cos(i*angleUnit));
+ }
  }
 
  void AudioDataAvailable(object sender, WaveInEventArgs e)
@@ -51,6 +64,17 @@ public void SetupGraphLabels()
  scottPlotUC2.fig.labelY = "Power (raw)";
  scottPlotUC2.fig.labelX = "Frequency (Hz)";
  scottPlotUC2.Redraw();
+
+ scottPlotHannPcm.fig.labelTitle = "Microphone Hann PCM Data";
+ scottPlotHannPcm.fig.labelY = "Amplitude (PCM)";
+ scottPlotHannPcm.fig.labelX = "Time (ms)";
+ scottPlotHannPcm.Redraw();
+
+ scottPlotHannFft.fig.labelTitle = "Microphone Hann FFT Data";
+ scottPlotHannFft.fig.labelY = "Power (raw)";
+ scottPlotHannFft.fig.labelX = "Frequency (Hz)";
+ scottPlotHannFft.Redraw();
+
  }
 
  public void StartListeningToMicrophone(int audioDeviceNumber = 0)
@@ -107,21 +131,41 @@ public void PlotLatestData()
 
  // create double arrays to hold the data we will graph
  double[] pcm = new double[graphPointCount];
- double[] fft = new double[graphPointCount];
- double[] fftReal = new double[graphPointCount/2];
-
+ double[] fftReal = new double[graphPointCount / 2];
+
  // populate Xs and Ys with double data
  for (int i = 0; i < graphPointCount; i++)
  {
  // read the int16 from the two bytes
- Int16 val = BitConverter.ToInt16(audioBytes, i * 2);
+ var val = BitConverter.ToInt16(audioBytes, i * 2);
 
  // store the value in Ys as a percent (+/- 100% = 200%)
- pcm[i] = (double)(val) / Math.Pow(2,16) * 200.0;
+ pcm[i] = (double)(val) / Math.Pow(2, 16) * 200.0;
  }
 
+
+ GraphData(graphPointCount, pcm, fftReal, scottPlotUC1, scottPlotUC2);
+
+ for (int i = 0; i < hannWindow.Length; i++)
+ pcm[i] *= hannWindow[i];
+
+ GraphData(graphPointCount, pcm, fftReal, scottPlotHannPcm, scottPlotHannFft);
+
+ //scottPlotUC1.PlotSignal(Ys, RATE);
+
+ numberOfDraws += 1;
+ lblStatus.Text = $"Analyzed and graphed PCM and FFT data {numberOfDraws} times";
+
+ // this reduces flicker and helps keep the program responsive
+ Application.DoEvents();
+
+ }
+
+ private void GraphData(int graphPointCount, double[] pcm, double[] fftReal,
+ ScottPlotUC scottPcm, ScottPlotUC scottFft)
+ {
  // calculate the full FFT
- fft = FFT(pcm);
+ var fft = FFT(pcm);
 
  // determine horizontal axis units for graphs
  double pcmPointSpacingMs = RATE / 1000;
@@ -130,29 +174,20 @@ public void PlotLatestData()
 
  // just keep the real half (the other half imaginary)
  Array.Copy(fft, fftReal, fftReal.Length);
- 
+
  // plot the Xs and Ys for both graphs
- scottPlotUC1.Clear();
- scottPlotUC1.PlotSignal(pcm, pcmPointSpacingMs, Color.Blue);
- scottPlotUC2.Clear();
- scottPlotUC2.PlotSignal(fftReal, fftPointSpacingHz, Color.Blue);
+ scottPcm.Clear();
+ scottPcm.PlotSignal(pcm, pcmPointSpacingMs, Color.Blue);
+ scottFft.Clear();
+ scottFft.PlotSignal(fftReal, fftPointSpacingHz, Color.Blue);
 
  // optionally adjust the scale to automatically fit the data
  if (needsAutoScaling)
  {
- scottPlotUC1.AxisAuto();
- scottPlotUC2.AxisAuto();
+ scottPcm.AxisAuto();
+ scottFft.AxisAuto();
  needsAutoScaling = false;
  }
-
- //scottPlotUC1.PlotSignal(Ys, RATE);
-
- numberOfDraws += 1;
- lblStatus.Text = $"Analyzed and graphed PCM and FFT data {numberOfDraws} times";
-
- // this reduces flicker and helps keep the program responsive
- Application.DoEvents(); 
-
  }
 
  private void autoScaleToolStripMenuItem_Click(object sender, EventArgs e)
@@ -186,5 +221,6 @@ public double[] FFT(double[] data)
  fft[i] = fftComplex[i].Magnitude;
  return fft;
  }
+
  }
 }