A helper function called internally by segment() for segmenting a single sound.
.segment(
audio,
shortestSyl = 40,
shortestPause = 40,
method = c("env", "spec", "mel")[3],
propNoise = NULL,
SNR = NULL,
noiseLevelStabWeight = c(1, 0.25),
windowLength = 40,
step = NULL,
overlap = 80,
reverbPars = list(reverbDelay = 70, reverbSpread = 130, reverbLevel = -35,
reverbDensity = 50),
interburst = NULL,
peakToTrough = SNR + 3,
troughLocation = c("left", "right", "both", "either")[4],
maxDur = 30,
saveAudio = NULL,
addSilence = 50,
plot = FALSE,
plotname = "",
savePlots = NULL,
main = NULL,
xlab = "",
ylab = "Signal, dB",
showLegend = FALSE,
width = 900,
height = 500,
units = "px",
res = NA,
maxPoints = c(1e+05, 5e+05),
specPlot = NULL,
contourPlot = list(lty = 1, lwd = 2, col = "green"),
sylPlot = list(lty = 1, lwd = 2, col = "blue"),
burstPlot = list(pch = 8, cex = 3, col = "red"),
...
)a list returned by readAudio
minimum acceptable length of syllables, ms
minimum acceptable break between syllables, ms (syllables separated by shorter pauses are merged)
the signal used to search for syllables: 'env' = Hilbert-transformed amplitude envelope, 'spec' = spectrogram, 'mel' = mel-transformed spectrogram (see tuneR::melfcc)
the proportion of non-zero sound assumed to represent background noise, 0 to 1 (note that complete silence is not considered, so padding with silence won't affect the algorithm)
expected signal-to-noise ratio (dB above noise), which determines the threshold for syllable detection. The meaning of "dB" here is approximate since the "signal" may be different from sound intensity
a vector of length 2 specifying the relative weights of the overall signal level vs. stability when attempting to automatically locate the regions that represent noise. Increasing the weight of stability tends to accentuate the beginning and end of each syllable.
length of FFT window, ms
you can override overlap by specifying FFT step, ms (NB:
because digital audio is sampled at discrete time intervals of
1/samplingRate, the actual step and thus the time stamps of STFT frames
may be slightly different, eg 24.98866 instead of 25.0 ms)
overlap between successive FFT frames, %
parameters passed on to reverb to attempt to
cancel the effects of reverberation or echo, which otherwise tend to merge
short and loud segments like rapid barks
minimum time between two consecutive bursts (ms). Defaults
to the average detected (syllable + pause) / 2
to qualify as a burst, a local maximum has to be at least
peakToTrough dB above the left and/or right local trough(s)
(controlled by troughLocation) over the analysis window (controlled
by interburst). Defaults to SNR + 3 dB
should local maxima be compared to the trough on the left and/or right of it? Values: 'left', 'right', 'both', 'either'
long files are split into chunks maxDur s in duration to
avoid running out of RAM; the outputs for all fragments are glued together,
but plotting is switched off. Note that noise profile is estimated in each
chunk separately, so set it low if the background noise is highly variable
full path to the folder in which to save audio files (one per detected syllable)
if syllables are saved as separate audio files, they can be padded with some silence (ms)
if TRUE, produces a segmentation plot
full path to the folder in which to save the plots (NULL = don't save, '' = same folder as audio)
main plotting parameters
if TRUE, shows a legend for thresholds
parameters passed to
png if the plot is saved
the maximum number of "pixels" in the oscillogram (if any) and spectrogram; good for quickly plotting long audio files; defaults to c(1e5, 5e5)
a list of graphical parameters for displaying the spectrogram
(if method = 'spec' or 'mel'); set to NULL to hide the spectrogram
a list of graphical parameters for displaying the signal contour used to detect syllables (see details)
a list of graphical parameters for displaying the syllables
a list of graphical parameters for displaying the bursts
other graphical parameters passed to graphics::plot