/// <summary>
/// A one-frame track sounds like a click.
/// A click is a sharp onset broadband sound of brief duration. Geometrically it is similar to a vertical whistle.
/// THis method averages dB log values incorrectly but it is faster than doing many log conversions.
/// This method is used to find acoustic events and is accurate enough for the purpose.
/// </summary>
public static (List <EventCommon> Events, double[] Intensity) GetOneFrameTracks(
SpectrogramStandard sonogram,
OneframeTrackParameters parameters,
TimeSpan segmentStartOffset)
{
var sonogramData = sonogram.Data;
int frameCount = sonogramData.GetLength(0);
int binCount = sonogramData.GetLength(1);
var frameStep = sonogram.FrameStep;
int nyquist = sonogram.NyquistFrequency;
double binWidth = nyquist / (double)binCount;
int minBin = (int)Math.Round(parameters.MinHertz.Value / binWidth);
int maxBin = (int)Math.Round(parameters.MaxHertz.Value / binWidth);
var decibelThreshold = parameters.DecibelThreshold.Value;
var minBandwidthHertz = parameters.MinBandwidthHertz.Value;
var maxBandwidthHertz = parameters.MaxBandwidthHertz.Value;
var converter = new UnitConverters(
segmentStartOffset: segmentStartOffset.TotalSeconds,
sampleRate: sonogram.SampleRate,
frameSize: sonogram.Configuration.WindowSize,
frameOverlap: sonogram.Configuration.WindowOverlap);
// Find all frame peaks and place in peaks matrix
// avoid row edge effects.
var peaks = new double[frameCount, binCount];
// for all time frames except 1st and last allowing for edge effects.
for (int t = 1; t < frameCount - 1; t++)
{
// buffer zone around click is one frame wide.
// for all frequency bins except top and bottom in this time frame
for (int bin = minBin; bin < maxBin; bin++)
{
if (sonogramData[t, bin] < decibelThreshold)
{
continue;
}
// THis is where the profile of a click is defined
// A click requires sudden onset, with maximum amplitude followed by decay.
bool isClickPeak = sonogramData[t - 1, bin] < decibelThreshold && sonogramData[t, bin] > sonogramData[t + 1, bin];
if (isClickPeak)
{
peaks[t, bin] = sonogramData[t, bin];
}
}
}
//NOTE: the Peaks matrix is same size as the sonogram.
var tracks = GetOneFrameTracks(peaks, minBin, maxBin, minBandwidthHertz, maxBandwidthHertz, decibelThreshold, converter);
// initialise tracks as events and get the combined intensity array.
var events = new List <EventCommon>();
var temporalIntensityArray = new double[frameCount];
var maxScore = decibelThreshold * 5;
foreach (var track in tracks)
{
var ae = new ClickEvent(track, maxScore)
{
SegmentStartSeconds = segmentStartOffset.TotalSeconds,
SegmentDurationSeconds = frameCount * converter.SecondsPerFrameStep,
Name = "noName",
};
events.Add(ae);
// fill the intensity array
var startRow = converter.FrameFromStartTime(track.StartTimeSeconds);
var amplitudeTrack = track.GetAmplitudeOverTimeFrames();
for (int i = 0; i < amplitudeTrack.Length; i++)
{
temporalIntensityArray[startRow + i] += amplitudeTrack[i];
}
}
// MAY NOT WANT TO Do THIS FOR ONE-FRAME tracks
// combine proximal events that occupy similar frequency band
//if (combineProximalSimilarEvents)
//{
// TimeSpan startDifference = TimeSpan.FromSeconds(0.5);
// int hertzDifference = 500;
// //######################################################################## TODO TODO TODOD
// //events = AcousticEvent.CombineSimilarProximalEvents(events, startDifference, hertzDifference);
//}
return(events, temporalIntensityArray);
}
/// <summary>
/// This method averages dB log values incorrectly but it is faster than doing many log conversions.
/// This method is used to find acoustic events and is accurate enough for the purpose.
/// </summary>
public static (List <EventCommon> ListOfevents, double[] CombinedIntensityArray) GetOnebinTracks(
SpectrogramStandard sonogram,
OnebinTrackParameters parameters,
TimeSpan segmentStartOffset)
{
var sonogramData = sonogram.Data;
int frameCount = sonogramData.GetLength(0);
int binCount = sonogramData.GetLength(1);
int nyquist = sonogram.NyquistFrequency;
double binWidth = nyquist / (double)binCount;
int minBin = (int)Math.Round(parameters.MinHertz.Value / binWidth);
int maxBin = (int)Math.Round(parameters.MaxHertz.Value / binWidth);
double decibelThreshold = parameters.DecibelThreshold.Value;
double minDuration = parameters.MinDuration.Value;
double maxDuration = parameters.MaxDuration.Value;
var converter = new UnitConverters(
segmentStartOffset: segmentStartOffset.TotalSeconds,
sampleRate: sonogram.SampleRate,
frameSize: sonogram.Configuration.WindowSize,
frameOverlap: sonogram.Configuration.WindowOverlap);
//Find all bin peaks and place in peaks matrix
var peaks = new double[frameCount, binCount];
for (int tf = 0; tf < frameCount; tf++)
{
for (int bin = minBin + 1; bin < maxBin - 1; bin++)
{
if (sonogramData[tf, bin] < decibelThreshold)
{
continue;
}
// here we define the amplitude profile of a whistle. The buffer zone around whistle is five bins wide.
var bandIntensity = ((sonogramData[tf, bin - 1] * 0.5) + sonogramData[tf, bin] + (sonogramData[tf, bin + 1] * 0.5)) / 2.0;
var topSidebandIntensity = (sonogramData[tf, bin + 3] + sonogramData[tf, bin + 4] + sonogramData[tf, bin + 5]) / 3.0;
var netAmplitude = 0.0;
if (bin < 4)
{
netAmplitude = bandIntensity - topSidebandIntensity;
}
else
{
var bottomSideBandIntensity = (sonogramData[tf, bin - 3] + sonogramData[tf, bin - 4] + sonogramData[tf, bin - 5]) / 3.0;
netAmplitude = bandIntensity - ((topSidebandIntensity + bottomSideBandIntensity) / 2.0);
}
if (netAmplitude >= decibelThreshold)
{
peaks[tf, bin] = sonogramData[tf, bin];
}
}
}
var tracks = GetOnebinTracks(peaks, minDuration, maxDuration, decibelThreshold, converter);
// Initialise tracks as events and get the combined intensity array.
var events = new List <WhistleEvent>();
var combinedIntensityArray = new double[frameCount];
var scoreRange = new Interval <double>(0, decibelThreshold * 5);
foreach (var track in tracks)
{
var ae = new WhistleEvent(track, scoreRange)
{
SegmentStartSeconds = segmentStartOffset.TotalSeconds,
SegmentDurationSeconds = frameCount * converter.SecondsPerFrameStep,
Name = "Whistle",
};
events.Add(ae);
// fill the intensity array
var startRow = converter.FrameFromStartTime(track.StartTimeSeconds);
var amplitudeTrack = track.GetAmplitudeOverTimeFrames();
for (int i = 0; i < amplitudeTrack.Length; i++)
{
combinedIntensityArray[startRow + i] = Math.Max(combinedIntensityArray[startRow + i], amplitudeTrack[i]);
}
}
// This algorithm tends to produce temporally overlapped whistle events in adjacent channels.
// Combine overlapping whistle events
var hertzDifference = 4 * binWidth;
var whistleEvents = WhistleEvent.CombineAdjacentWhistleEvents(events, hertzDifference);
// Finally filter the whistles for presense of excess noise in buffer band just above the whistle.
// Excess noise would suggest this is not a whistle event.
var bufferHertz = 300;
var bufferBins = (int)Math.Round(bufferHertz / binWidth);
var filteredEvents = new List <EventCommon>();
foreach (var ev in whistleEvents)
{
var avNhAmplitude = GetAverageAmplitudeInNeighbourhood((SpectralEvent)ev, sonogramData, bufferBins, converter);
Console.WriteLine($"###################################Buffer Average decibels = {avNhAmplitude}");
if (avNhAmplitude < decibelThreshold)
{
// There is little acoustic activity in the buffer zone above the whistle. It is likely to be a whistle.
filteredEvents.Add(ev);
}
}
return(filteredEvents, combinedIntensityArray);
}