Class OnebinTrackAlgorithm

This class searches a spectrogram for whistles, that is, for tones or spectral peaks that persist in one frequency bin. In practice, the whistles of birds and other natural sources do not occupy a single frequency bin, although this statement is confounded by the choice of recording sample rate and frame size. But typically, a bird whistle spreads itself across three or more frequency bins using typical values for SR etc. In this class, we make an assumption about the spectral profile of a whistle and the user is expected to find the appropriate sample rate, frame size and frame step such that the target whistle is detected using the profile. We define a whistle profile that is 11 bins wide. The actual whistle occupies the centre three bins, ie bins -1, 0 , +1. Bins -2 and +2 are ignored to allow for some flexibility in getting he right combination of sample rate, frame size and frame step. To establish that the centre three bins contain a spectral peak (i.e. are part of a potential whistle), we define top and bottom sidebands, each of width three bins. These are used to establish a baseline intensity which must be less than that of the centre three bins. The bottom sideband = bins -3, -4, -5. The top sideband = bins +3, +4, +5. Defining a whistle this way introduces edge effects at the top and bottom of the spectrogram. In case of the low frequency edge, in order to get as close as possible to the frequency bin zero, we do not incorporate a bottom sidebound into the calculations. Also note that a typical bird whistle is not exactly a pure tone. It typically fluctuates slightly from one frequency bin to an adjacent bin and back. Consequently a final step in this whistle detection algorithm is to merge adjacent whistle tracks. The algorithm is not perfect but it does detect constant tone sounds. Theis algorithm is designed so as not to pick up chirps, i.e. gradually rising and falling tones. However, here again the right choice of SR, frame size and frame step are important.

Inheritance

Object

OnebinTrackAlgorithm

Inherited Members

Object.Equals(Object)

Object.Equals(Object, Object)

Object.GetHashCode()

Object.GetType()

Object.MemberwiseClone()

Object.ReferenceEquals(Object, Object)

Object.ToString()

Namespace: AudioAnalysisTools.Tracks

Assembly: AudioAnalysisTools.dll

Syntax

public static class OnebinTrackAlgorithm

Methods

GetOnebinTrack(Double[,], Int32, Int32, Double, UnitConverters)

Declaration

public static Track GetOnebinTrack(double[, ] peaks, int startRow, int bin, double threshold, UnitConverters converter)

Parameters

Type	Name	Description
Double[,]	peaks
Int32	startRow
Int32	bin
Double	threshold
UnitConverters	converter

Returns

Type	Description
Track

GetOnebinTracks(SpectrogramStandard, OnebinTrackParameters, Nullable<Double>, TimeSpan, String)

Declaration

public static (List<EventCommon> Events, List<Plot> DecibelPlots) GetOnebinTracks(SpectrogramStandard spectrogram, OnebinTrackParameters parameters, double? decibelThreshold, TimeSpan segmentStartOffset, string profileName)

Parameters

Type	Name	Description
SpectrogramStandard	spectrogram
OnebinTrackParameters	parameters
Nullable<Double>	decibelThreshold
TimeSpan	segmentStartOffset
String	profileName

Returns

Type	Description
(T1, T2)<List<EventCommon>, List<Plot>>

GetOnebinTracks(SpectrogramStandard, OnebinTrackParameters, TimeSpan, Double)

This method returns whistle (spectral peak) tracks enclosed as spectral events. It averages dB log values incorrectly but it is faster than doing many log conversions.

Declaration

public static (List<EventCommon> ListOfevents, double[] CombinedIntensityArray) GetOnebinTracks(SpectrogramStandard spectrogram, OnebinTrackParameters parameters, TimeSpan segmentStartOffset, double decibelThreshold)

Parameters

Type	Name	Description
SpectrogramStandard	spectrogram	The spectrogram to be searched.
OnebinTrackParameters	parameters	The parameters that determine the search.
TimeSpan	segmentStartOffset	Enables assignment of a start time (relative to recording) to any valid event.
Double	decibelThreshold	The threshold for detection of a track.

Returns

Type	Description
(T1, T2)<List<EventCommon>, Double[]>	A list of acoustic events containing whistle tracks.

GetOnebinTracks(Double[,], Double, Double, Double, UnitConverters)

This method finds whistle tracks, that is horizontal ridges in one frequency bin.

Declaration

public static List<Track> GetOnebinTracks(double[, ] peaks, double minDuration, double maxDuration, double threshold, UnitConverters converter)

Parameters

Type	Name	Description
Double[,]	peaks	Peaks matrix.
Double	minDuration	Minimum duration of a whistle.
Double	maxDuration	Maximum duration of a whistle.
Double	threshold	Minimum amplitude threshold to be valid whistle.
UnitConverters	converter	For the time/frequency scales.

Returns

Type	Description
List<Track>	A list of whistle tracks.