Setting default FFT window to Hanning

Issue #291 Have set the default FFT window to Hanning for calculation of all summary and spectral indices.
However left the Test methods using HAMMING window so do not have to make changes to the output.

src/AnalysisPrograms/Create4Sonograms.cs

@@ -112,7 +112,7 @@ public static void Main(Arguments arguments)
 
             var recording = new AudioRecording(fiOutputSegment.FullName);
 
-            // EXTRACT ENVELOPE and SPECTROGRAM
+            // EXTRACT ENVELOPE and SPECTROGRAM// This call uses the default FFT window.
             var dspOutput = DSP_Frames.ExtractEnvelopeAndFfts(recording, frameSize, windowOverlap);
 
             // average absolute value over the minute recording

src/AnalysisPrograms/SnrAnalysis.cs

@@ -114,6 +114,7 @@ public static void Execute(Arguments arguments)
             int frameCount = signalLength / stepSize;
 
             // (B) ################################## EXTRACT ENVELOPE and SPECTROGRAM ##################################
+            // Calling this method will set the default FFT window.
             var dspOutput = DSP_Frames.ExtractEnvelopeAndFfts(
                 recording,
                 sonoConfig.WindowSize,

src/AudioAnalysisTools/DSP/DSP_Frames.cs

@@ -133,22 +133,31 @@ public static int FrameStep(int windowSize, double windowOverlap)
             return frames;
         }
 
+        /// <summary>
+        /// Calling this method will set default FFT window if windowName is null.
+        /// Otherwise sets the FFT window specified in the config file.
+        /// </summary>
         public static EnvelopeAndFft ExtractEnvelopeAndFfts(AudioRecording recording, int frameSize, double overlap, string windowName = null)
         {
             int frameStep = (int)(frameSize * (1 - overlap));
             return ExtractEnvelopeAndAmplSpectrogram(recording.WavReader.Samples, recording.SampleRate, recording.Epsilon, frameSize, frameStep, windowName);
         }
 
+        /// <summary>
+        /// Calling this method sets the default FFT window, currently HANNING - see FFT.cs line 22.
+        /// </summary>
         public static EnvelopeAndFft ExtractEnvelopeAndFfts(AudioRecording recording, int frameSize, int frameStep)
         {
-            string windowName = FFT.KeyHammingWindow;
-            return ExtractEnvelopeAndAmplSpectrogram(recording.WavReader.Samples, recording.SampleRate, recording.Epsilon, frameSize, frameStep, windowName);
+            return ExtractEnvelopeAndAmplSpectrogram(recording.WavReader.Samples, recording.SampleRate, recording.Epsilon, frameSize, frameStep, FFT.DefaultFftWindow);
         }
 
+        /// <summary>
+        /// Calling this method sets the default FFT window, currently HANNING - see FFT.cs line 22.
+        /// </summary>
         public static EnvelopeAndFft ExtractEnvelopeAndAmplSpectrogram(double[] signal, int sampleRate, double epsilon, int frameSize, double overlap)
         {
             int frameStep = (int)(frameSize * (1 - overlap));
-            return ExtractEnvelopeAndAmplSpectrogram(signal, sampleRate, epsilon, frameSize, frameStep, FFT.KeyHammingWindow);
+            return ExtractEnvelopeAndAmplSpectrogram(signal, sampleRate, epsilon, frameSize, frameStep, FFT.DefaultFftWindow);
         }
 
         /// <summary>
@@ -196,7 +205,7 @@ public static EnvelopeAndFft ExtractEnvelopeAndAmplSpectrogram(
             // set up the FFT parameters
             if (windowName == null)
             {
-                windowName = FFT.KeyHammingWindow;
+                windowName = FFT.DefaultFftWindow;
             }
 
             FFT.WindowFunc w = FFT.GetWindowFunction(windowName);

src/TowseyLibrary/FFT.cs

@@ -19,6 +19,7 @@ public sealed class FFT
         public const string KeyNoWindow = "NONE";
         public const string KeyHammingWindow = "HAMMING";
         public const string KeyHanningWindow = "HANNING";
+        public const string DefaultFftWindow = KeyHanningWindow;
 
         public delegate double WindowFunc(int n, int N);
 
@@ -338,9 +339,13 @@ private static double lrw(double a0, double a1, double a2, double a3, int n, int
             return 1.0 - (1.93 * c1) + (1.29 * c2) - (0.388 * c3) + (0.032 * c4);
         };
 
+        /// <summary>
+        /// Returns an FFT window function given the name of the window type.
+        /// </summary>
+        /// <param name="name">FFT window name.</param>
+        /// <returns>FFT.WindowFunc.</returns>
         public static WindowFunc GetWindowFunction(string name)
         {
-            //FFT.WindowFunc windowFnc;
             if (name.StartsWith(KeyHammingWindow))
             {
                 return Hamming;