public static IEnumerable <string> CompareSamplingRates()
{
const float filterFrequency = 150;
const float frameSizeInS = 0.1f;
var sampleRates = new[] { 600, 8000, 48000 };
var hammings = sampleRates.Select(sr => FFTWindowBuilder.Hamming((int)(sr * frameSizeInS))).ToArray();
var responses = new float[sampleRates.Length];
for (int i = 1; i < 300; i++)
{
for (int j = 0; j < sampleRates.Length; j++)
{
var signal = SignalGenerator.Sinus(sampleRates[j], frameSizeInS, i).ToArray();
responses[j] = GoertzelMag(signal, sampleRates[j], filterFrequency, hammings[j], out _);
}
yield return($"{i};" + string.Join(";", responses.Select(r => r.ToString(CultureInfo.InvariantCulture))));
}
}
public static IEnumerable <string> CompareFrameSizes()
{
const float filterFrequency = 150;
var frameSizesInS = new float[] { 0.1f, 0.5f };
var sampleRate = 48000;
var hammings = frameSizesInS.Select(fs => FFTWindowBuilder.Hamming((int)(fs * sampleRate))).ToArray();
var responses = new float[frameSizesInS.Length];
for (int i = 1; i < 300; i++)
{
for (int j = 0; j < frameSizesInS.Length; j++)
{
var signal = SignalGenerator.Sinus(sampleRate, frameSizesInS[j], i).ToArray();
responses[j] = GoertzelMag(signal, sampleRate, filterFrequency, hammings[j], out _);
}
yield return($"{i};" + string.Join(";", responses.Select(r => r.ToString(CultureInfo.InvariantCulture))));
}
}
public static IEnumerable <string> CompareFilterWindows()
{
const float filterFrequency = 150;
const float frameSizeInS = 0.1f;
const int sampleRate = 48000;
int windowSize = (int)(frameSizeInS * sampleRate);
var windows = new[] {
FFTWindowBuilder.Blackmann(windowSize),
FFTWindowBuilder.Hamming(windowSize),
FFTWindowBuilder.Hann(windowSize),
FFTWindowBuilder.Door(windowSize)
};
var responses = new float[windows.Length];
for (int i = 1; i < 300; i++)
{
var signal = SignalGenerator.Sinus(sampleRate, frameSizeInS, i).ToArray();
for (int j = 0; j < windows.Length; j++)
{
responses[j] = GoertzelMag(signal, sampleRate, filterFrequency, windows[j], out _);
}
yield return($"{i};" + string.Join(";", responses.Select(r => r.ToString(CultureInfo.InvariantCulture))));
}
}