Measure relative sound pressure level

sound_pressure_level measures relative (uncalibrated) sound pressure level in signals referenced in a selection table.

Usage

sound_pressure_level(X, reference = 20, parallel = 1, path = NULL, pb = TRUE,
type = "single", wl = 100, bp = NULL, remove.bgn = FALSE, mar = NULL, envelope = "abs")

Arguments

X

object of class 'selection_table', 'extended_selection_table' or any data frame with columns for sound file name (sound.files), selection number (selec), and start and end time of signal (start and end).

reference

Numeric vector of length 1 indicating the pressure (in µPa) to be used as reference. Alternatively, a character vector with the name of a numeric column containing reference values for each row can be supplied. Default is 20 (µPa). NOT YET IMPLEMENTED.

parallel

Numeric. Controls whether parallel computing is applied. It specifies the number of cores to be used. Default is 1 (i.e. no parallel computing). It can also be set globally using the 'parallel' option (see warbleR_options).

path

Character string containing the directory path where the sound files are located. If NULL (default) then the current working directory is used. It can also be set globally using the 'wav.path' option (see warbleR_options).

pb

Logical argument to control if progress bar is shown. Default is TRUE. It can also be set globally using the 'pb' option (see warbleR_options).

type

Character string controlling how SPL is measured: #'

single: single SPL value obtained on the entire signal. Default.
mean: average of SPL values measured across the signal.
peak: maximum of several SPL values measured across the signal.

wl

A numeric vector of length 1 specifying the spectrogram window length. Default is 512.

bp

Numeric vector of length 2 giving the lower and upper limits of a frequency bandpass filter (in kHz). Alternatively, when set to 'freq.range', the function will use the 'bottom.freq' and 'top.freq' for each signal as the bandpass range. Default is NULL (no bandpass filter).

remove.bgn

Logical argument to control if SPL from background noise is excluded from the measured signal SPL. Default is FALSE.

mar

numeric vector of length 1. Specifies the margins adjacent to the start point of selection over which to measure background noise.

envelope

Character string vector with the method to calculate amplitude envelopes (in which SPL is measured), as in env. Must be either 'abs' (absolute envelope, default) or 'hil' (Hilbert transformation).

Value

The object supplied in 'X' with a new variable with the sound pressure level values ('SPL' or 'peak.amplitude' column, see argument 'peak.amplitude') in decibels.

Details

Sound pressure level (SPL) is a logarithmic measure of the effective pressure of a sound relative to a reference, so it's a measure of sound intensity. SPL is measured as the root mean square of the amplitude vector, and as such is only a useful metric of the variation in loudness for signals within the same recording (or recorded with the same equipment and gain).

References

Araya-Salas, M., & Smith-Vidaurre, G. (2017). warbleR: An R package to streamline analysis of animal acoustic signals. Methods in Ecology and Evolution, 8(2), 184-191. Wikipedia: Sound pressure level

Author

Marcelo Araya-Salas (marcelo.araya@ucr.ac.cr) and Grace Smith Vidaurre

Examples

{
  data(list = c("Phae.long1", "lbh_selec_table"))
  writeWave(Phae.long1, file.path(tempdir(), "Phae.long1.wav")) # save sound files

  spl <- sound_pressure_level(
    X = lbh_selec_table[grep("Phae.long1", lbh_selec_table$sound.files), ],
    parallel = 1, pb = TRUE, path = tempdir()
  )
}