public void GenerateFrequencyDomainImpulseResponse_CheckDistanceAttenuation()
{
var sampleRate = 16000;
var dftLength = 1024;
var delaySampleCount = 30;
var time = (double)delaySampleCount / sampleRate;
var distance = AcousticConstants.SoundSpeed * time;
var roomSize = DenseVector.OfArray(new double[] { distance, distance, distance });
var distanceAttenuation = new DistanceAttenuation(distance => distance < 0.1 ? 3.1 : 2.3);
var reflectionAttenuation = new ReflectionAttenuation(frequency => 0.7);
var room = new Room(roomSize, distanceAttenuation, reflectionAttenuation, 1);
var soundSource = new SoundSource(distance / 2, distance / 2, distance / 2);
var microphone = new Microphone(distance / 2, distance / 2, distance / 2);
var response = MirrorMethod.GenerateFrequencyDomainImpulseResponse(room, soundSource, microphone, sampleRate, dftLength);
var timeDomainSignal = new Complex[dftLength];
timeDomainSignal[0] = response[0];
for (var w = 1; w < dftLength / 2; w++)
{
timeDomainSignal[w] = response[w];
timeDomainSignal[dftLength - w] = response[w].Conjugate();
}
timeDomainSignal[dftLength / 2] = response[dftLength / 2];
Fourier.Inverse(timeDomainSignal, FourierOptions.AsymmetricScaling);
for (var t = 0; t < dftLength; t++)
{
if (t == 0)
{
Assert.AreEqual(3.1, timeDomainSignal[t].Real, 1.0E-6);
Assert.AreEqual(0.0, timeDomainSignal[t].Imaginary, 1.0E-6);
}
else if (t == delaySampleCount)
{
Assert.AreEqual(6 * 2.3 * 0.7, timeDomainSignal[t].Real, 1.0E-6);
Assert.AreEqual(0.0, timeDomainSignal[t].Imaginary, 1.0E-6);
}
else
{
Assert.AreEqual(0.0, timeDomainSignal[t].Real, 1.0E-6);
Assert.AreEqual(0.0, timeDomainSignal[t].Imaginary, 1.0E-6);
}
}
}
public void GenerateFrequencyDomainImpulseResponse_CheckReflectionAttenuation()
{
var sampleRate = 16000;
var dftLength = 1024;
var delaySampleCount = 30;
var time = (double)delaySampleCount / sampleRate;
var distance = AcousticConstants.SoundSpeed * time;
var cutOff = 4000;
var roomSize = DenseVector.OfArray(new double[] { distance, distance, distance });
var distanceAttenuation = new DistanceAttenuation(distance => distance < 1.0E-3 ? 0.0 : 0.9);
var reflectionAttenuation = new ReflectionAttenuation(frequency => frequency < cutOff ? 0.7 : 0.0);
var room = new Room(roomSize, distanceAttenuation, reflectionAttenuation, 1);
var soundSource = new SoundSource(distance / 2, distance / 2, distance / 2);
var microphone = new Microphone(distance / 2, distance / 2, distance / 2);
var response = MirrorMethod.GenerateFrequencyDomainImpulseResponse(room, soundSource, microphone, sampleRate, dftLength);
var validCount = 0;
for (var w = 0; w < response.Length; w++)
{
var frequency = (double)w / dftLength * sampleRate;
if (Math.Abs(frequency - cutOff) > 1)
{
if (frequency < cutOff)
{
Assert.IsTrue(response[w].Magnitude > 1.0E-3);
}
else
{
Assert.IsTrue(response[w].Magnitude < 1.0E-3);
}
validCount++;
}
}
Assert.IsTrue(validCount >= response.Length - 3);
}