public void TestBandStop12()
{
const int order = 12;
const double fs = 32000d;
const double cutoffFrequency = 1000d;
const double br = 10;
const double error = 1e-2;
var coeff = new BandStopChebyshevIICoefficients(order, fs, cutoffFrequency - br, cutoffFrequency + br, 48);
var chain = coeff.Calculate();
var expected = Helpers.LoadCsv(
@"0.991883, -1.945553, 0.991883, 1.000000, -1.959391, 0.997890
1.000000, -1.961674, 1.000000, 1.000000, -1.959624, 0.997896
1.000000, -1.961280, 1.000000, 1.000000, -1.959306, 0.998028
1.000000, -1.961866, 1.000000, 1.000000, -1.959988, 0.998045
1.000000, -1.961105, 1.000000, 1.000000, -1.959375, 0.998302
1.000000, -1.962038, 1.000000, 1.000000, -1.960458, 0.998325
1.000000, -1.960962, 1.000000, 1.000000, -1.959597, 0.998694
1.000000, -1.962177, 1.000000, 1.000000, -1.961001, 0.998717
1.000000, -1.960860, 1.000000, 1.000000, -1.959955, 0.999178
1.000000, -1.962276, 1.000000, 1.000000, -1.961581, 0.999195
1.000000, -1.960807, 1.000000, 1.000000, -1.960426, 0.999719
1.000000, -1.962326, 1.000000, 1.000000, -1.962159, 0.999725").ToList();
var expectedGain = 0.985211119221826;
Assert.AreEqual(expected.Count, chain.Count);
for (int i = 0; i < expected.Count; i++)
{
Helpers.ValidateBiquad(expected[i], chain[i], error);
}
}
public void TestBandStop08()
{
const int order = 8;
const double fs = 44100d;
const double cutoffFrequency = 500d;
const double br = 5;
const double error = 1e-3;
var coeff = new BandStopChebyshevIICoefficients(order, fs, cutoffFrequency - br, cutoffFrequency + br, 48);
var chain = coeff.Calculate();
var expected = Helpers.LoadCsv(
@"0.996871, -1.988667, 0.996871, 1.000000, -1.993703, 0.998799
1.000000, -1.994948, 1.000000, 1.000000, -1.993761, 0.998805
1.000000, -1.994871, 1.000000, 1.000000, -1.993832, 0.998977
1.000000, -1.994984, 1.000000, 1.000000, -1.993995, 0.998991
1.000000, -1.994843, 1.000000, 1.000000, -1.994131, 0.999314
1.000000, -1.995011, 1.000000, 1.000000, -1.994368, 0.999328
1.000000, -1.994827, 1.000000, 1.000000, -1.994554, 0.999758
1.000000, -1.995026, 1.000000, 1.000000, -1.994822, 0.999765").ToList();
var expectedGain = 0.996359732766342;
Assert.AreEqual(expected.Count, chain.Count);
for (int i = 0; i < expected.Count; i++)
{
Helpers.ValidateBiquad(expected[i], chain[i], error);
}
}
public void TestBandStopChebyshevIIFiltering()
{
const int order = 16;
const int fs = 44100;
const double f1 = 500d;
const double f2 = 8000d;
const int cycles = 10;
double[] frequencies = { 330, 770, 1870, 5830, 9790 };
var validFrequencies = frequencies.TakeWhile(f => f < f1).Concat(frequencies.SkipWhile(f => f < f2));
var coeff = new BandStopChebyshevIICoefficients(order, fs, f1, f2, 48);
TestFilter(order, fs, cycles, coeff, frequencies, validFrequencies);
}
public void TestBandStopSinusoid()
{
const int order = 16;
const int fs = 44100;
const int targetFrequency = 3;
const double br = 5;
const int cycles = 10;
double[] frequencies =
{ 65.406, 130.81, 261.63, 523.25, 1046.5, 2093.0, 4186.0, 8372.0 };
var signal = new double[cycles * fs];
foreach (var frequency in frequencies)
{
Helpers.GenerateSinusoid(frequency, fs, signal);
}
var im = new double[signal.Length];
var coeff = new BandStopChebyshevIICoefficients(order, fs, frequencies[targetFrequency] - br, frequencies[targetFrequency] + br, 48);
var chain = coeff.Calculate();
chain.Filter(signal, 0, signal, 0, signal.Length);
var count = signal.Length / 2;
FourierTransform2.FFT(signal, im, FourierTransform.Direction.Forward);
Helpers.CalculateEnergy(signal, im, count);
var maxEnergy = signal.Take(count).Max();
var step = fs / (2d * count);
var peakSet = new HashSet <double>();
for (int i = 1; i < count - 1; i++)
{
var freq = i * step;
if (signal[i] > signal[i - 1] && signal[i] > signal[i + 1] && signal[i] >= 0.01 * maxEnergy)
{
var peak = frequencies.FirstOrDefault(x => Math.Abs(freq - x) <= 1);
Assert.AreNotEqual(0, peak);
peakSet.Add(peak);
}
}
Assert.IsTrue(peakSet.SetEquals(frequencies.Except(Enumerable.Repeat(frequencies[targetFrequency], 1))));
}
public void TestBandStop16()
{
const int order = 16;
const double fs = 31250d;
const double cutoffFrequency = 60;
const double br = 1;
const double error = 1e-3;
var coeff = new BandStopChebyshevIICoefficients(order, fs, cutoffFrequency - br, cutoffFrequency + br, 48);
var chain = coeff.Calculate();
var expected = Helpers.LoadCsv(
@"0.999183, -1.998220, 0.999183, 1.000000, -1.999694, 0.999840
1.000000, -1.999855, 1.000000, 1.000000, -1.999696, 0.999841
1.000000, -1.999853, 1.000000, 1.000000, -1.999699, 0.999846
1.000000, -1.999856, 1.000000, 1.000000, -1.999703, 0.999847
1.000000, -1.999852, 1.000000, 1.000000, -1.999710, 0.999857
1.000000, -1.999857, 1.000000, 1.000000, -1.999717, 0.999860
1.000000, -1.999851, 1.000000, 1.000000, -1.999726, 0.999875
1.000000, -1.999858, 1.000000, 1.000000, -1.999735, 0.999878
1.000000, -1.999851, 1.000000, 1.000000, -1.999747, 0.999897
1.000000, -1.999858, 1.000000, 1.000000, -1.999758, 0.999900
1.000000, -1.999850, 1.000000, 1.000000, -1.999773, 0.999923
1.000000, -1.999859, 1.000000, 1.000000, -1.999785, 0.999926
1.000000, -1.999850, 1.000000, 1.000000, -1.999802, 0.999953
1.000000, -1.999859, 1.000000, 1.000000, -1.999814, 0.999954
1.000000, -1.999850, 1.000000, 1.000000, -1.999833, 0.999984
1.000000, -1.999859, 1.000000, 1.000000, -1.999844, 0.999985").ToList();
var expectedGain = 0.997950883359409;
Assert.AreEqual(expected.Count, chain.Count);
for (int i = 0; i < expected.Count; i++)
{
Helpers.ValidateBiquad(expected[i], chain[i], error);
}
}
