energy_detector {ohun}

Detects the start and end of sound events

Description

energy_detector detects the start and end of sound events based on energy and time attributes

Usage

energy_detector(files = NULL, envelopes = NULL, path = ".", hop.size = 11.6, wl = NULL,
thinning = 1, bp = NULL, smooth = 5, threshold = 5, peak.amplitude = 0,
hold.time = 0, min.duration = 0, max.duration = Inf, cores = 1, pb = TRUE)

Arguments

files

Character vector indicating the sound files that will be analyzed. Optional. If 'files' and 'envelopes' are not supplied then the function will work on all supported format sound files in the working directory. Supported file formats:'.wav', '.mp3', '.flac' and '.wac'. If not supplied the function will work on all sound files (in the supported format) in 'path'.

envelopes

An object of class 'envelopes' (generated by get_envelopes) containing the amplitude envelopes of the sound files to be analyzed. If 'files' and 'envelopes' are not supplied then the function will work on all supported format sound files in the working directory.

path

Character string containing the directory path where the sound files are located. The current working directory is used as default.

hop.size

A numeric vector of length 1 specifying the time window duration (in ms). Default is 11.6 ms, which is equivalent to 512 wl for a 44.1 kHz sampling rate. Ignored if 'wl' is supplied.

wl

A numeric vector of length 1 specifying the window length of the spectrogram. Default is NULL. If supplied, 'hop.size' is ignored. Used internally for bandpass filtering (so only applied when 'bp' is supplied).

thinning

Numeric vector of length 1 in the range 0~1 indicating the proportional reduction of the number of samples used to represent amplitude envelopes (i.e. the thinning of the envelopes). Usually amplitude envelopes have many more samples than those needed to accurately represent amplitude variation in time, which affects the size of the output (usually very large R objects / files). Default is 1 (no thinning). Higher sampling rates can afford higher size reduction (e.g. lower thinning values). Reduction is conducted by interpolation using approx. Note that thinning may decrease time precision, and the higher the thinning the less precise the time detection. This argument is used internally by get_envelopes. Not used if 'envelopes' are supplied.

bp

Numeric vector of length 2 giving the lower and upper limits of a frequency bandpass filter (in kHz). Default is NULL. This argument is used internally by get_envelopes. Not used if 'envelopes' are supplied. Bandpass is done using the function ffilter, which applies a short-term Fourier transformation to first create a spectrogram in which the target frequencies are filtered and then is back transformed into a wave object using a reverse Fourier transformation.

smooth

A numeric vector of length 1 to smooth the amplitude envelope with a sum smooth function. It controls the time 'neighborhood' (in ms) in which amplitude samples are smoothed (i.e. averaged with neighboring samples). Default is 5. 0 means no smoothing is applied. Note that smoothing is applied before thinning (see 'thinning' argument). The function envelope is used internally which is analogous to sum smoothing in env. This argument is used internally by get_envelopes. Not used if 'envelopes' are supplied.

threshold

Numeric vector of length 1 with a value between 0 and 100 specifying the amplitude threshold for detecting sound event occurrences. Amplitude is represented as a percentage so 0 and 100 represent the lowest amplitude and highest amplitude respectively. Default is 5.

peak.amplitude

Numeric vector of length 1 with the minimum peak amplitude value. Detections below that value are excluded. Peak amplitude is the maximum sound pressure level (in decibels) across the sound event (see sound_pressure_level). This can be useful when expecting higher peak amplitude in the target sound events compared to non-target sound events or when keeping only the best examples of the target sound events. Default is 0.

hold.time

Numeric vector of length 1. Specifies the time range (in ms) at which selections will be merged (i.e. if 2 selections are separated by less than the specified 'hold.time' they will be merged in to a single selection). Default is 0 (no hold time applied).

min.duration

Numeric vector of length 1 giving the shortest duration (in ms) of the sound events to be detected. It removes sound events below that threshold. If 'hold.time' is supplied sound events are first merged and then filtered by duration. Default is 0 (i.e. no filtering based on minimum duration).

max.duration

Numeric vector of length 1 giving the longest duration (in ms) of the sound events to be detected. It removes sound events above that threshold. If 'hold.time' is supplied sound events are first merged and then filtered by duration. Default is Inf (i.e. no filtering based on maximum duration).

cores

Numeric. Controls whether parallel computing is applied. It specifies the number of cores to be used. Default is 1 (i.e. no parallel computing).

pb

Logical argument to control progress bar. Default is TRUE.

Details

This function detects the time position of target sound events based on energy and time thresholds. It first detect all sound above a given energy threshold (argument 'energy'). If 'hold.time' is supplied then detected sounds are merged if necessary. Then the sounds detected are filtered based on duration attributes ('min.duration' and 'max.duration'). If 'peak.amplitude' is higher than 0 then only those sound events with higher peak amplitude are kept. Band pass filtering ('bp'), thinning ('thinning') and envelope smoothing ('smooth') are applied (if supplied) before threshold detection.

Value

The function returns a 'selection_table' (warbleR package's formats, see selection_table) or data frame (if sound files can't be found) containing the start and end of each sound event by sound file. If no sound event was detected for a sound file it is not included in the output data frame.

Author(s)

Marcelo Araya-Salas ([e-mail])

References

Araya-Salas, M., Smith-Vidaurre, G., Chaverri, G., Brenes, J. C., Chirino, F., Elizondo-Calvo, J., & Rico-Guevara, A. 2022. ohun: an R package for diagnosing and optimizing automatic sound event detection. BioRxiv, 2022.12.13.520253. https://doi.org/10.1101/2022.12.13.520253

See Also

optimize_energy_detector

Examples

# Save example files into temporary working directory
data("lbh1", "lbh2", "lbh_reference")
tuneR::writeWave(lbh1, file.path(tempdir(), "lbh1.wav"))
tuneR::writeWave(lbh2, file.path(tempdir(), "lbh2.wav"))

# using smoothing and minimum duration
detec <- energy_detector(files = c("lbh1.wav", "lbh2.wav"),
path = tempdir(), threshold = 6, smooth = 6.8,
bp = c(2, 9), hop.size = 3, min.duration = 0.05)

# diagnose detection
diagnose_detection(reference = lbh_reference,
detection = detec)

# without declaring 'files'
detec <- energy_detector(path = tempdir(), threshold = 60, smooth = 6.8,
bp = c(2, 9), hop.size = 6.8, min.duration = 90)

# diagnose detection
diagnose_detection(reference = lbh_reference,
detection = detec)

# using hold time
detec <- energy_detector(threshold = 10, hold.time = 150,
bp = c(2, 9), hop.size = 6.8, path = tempdir())

# diagnose detection
diagnose_detection(reference = lbh_reference, detection = detec)

# calculate envelopes first
envs <- get_envelopes(bp = c(2, 9), hop.size = 6.8, path = tempdir())

# then run detection providing 'envelopes' (but no 'files')
detec <- energy_detector(envelopes = envs, threshold = 10, hold.time = 150, min.duration = 50)

# diagnose detection
diagnose_detection(reference = lbh_reference, detection = detec, time.diagnostics = TRUE)

# USIN OTHER SOUND FILE FORMAT (flac program must be installed)
 # fisrt convert files to flac
 warbleR::wav_2_flac(path = tempdir())

 # change sound file extension to flac
 flac_reference <- lbh_reference
 flac_reference$sound.files <- gsub(".wav", ".flac", flac_reference$sound.files)

 # run detection
 detec <- energy_detector(files = c("lbh1.flac", "lbh2.flac"), path = tempdir(), threshold = 60,
 smooth = 6.8, bp = c(2, 9), hop.size = 6.8, min.duration = 90)

 # diagnose detection
 diagnose_detection(reference = flac_reference, detection = detec)