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sig2noise measures signal-to-noise ratio across multiple files.
sig2noise(X, mar, parallel = 1, path = NULL, pb = TRUE, type = 1, eq.dur = FALSE,
in.dB = TRUE, before = FALSE, lim.dB = TRUE, bp = NULL, wl = 10)'selection.table' object or data frame with results from manualoc 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).
numeric vector of length 1. Specifies the margins adjacent to the start and end points of selection over which to measure noise.
Numeric. Controls whether parallel computing is applied. It specifies the number of cores to be used. Default is 1 (i.e. no parallel computing).
Character string containing the directory path where the sound files are located.
If NULL (default) then the current working directory is used.
Logical argument to control progress bar. Default is TRUE.
Numeric. Determine the formula to be used to calculate the signal-to-noise ratio (S = signal , N = background noise):
1: ratio of S mean amplitude envelope to
N mean amplitude envelope (mean(env(S))/mean(env(N)))
2: ratio of S amplitude envelope quadratic mean to N amplitude envelope quadratic mean
(rms(env(S))/rms(env(N)))
3: ratio of the difference between S amplitude envelope quadratic mean and N amplitude envelope quadratic mean to N amplitude envelope quadratic mean ((rms(env(S)) - rms(env(N)))/rms(env(N)))
Logical. Controls whether the noise segment that is measured has the same duration
than the signal (if TRUE, default FALSE). If TRUE then mar argument is ignored.
Logical. Controls whether the signal-to-noise ratio is returned in decibels (20*log10(SNR)).
Default is TRUE.
Logical. If TRUE noise is only measured right before the signal (instead of before and after). Default is FALSE.
Logical. If TRUE the lowest signal-to-noise would be limited to -40 dB (if in.dB = TRUE). This would remove NA's that can be produced when noise segments have a higher amplitude than the signal
itself. Default is TRUE.
Numeric vector of length 2 giving the lower and upper limits of a frequency bandpass filter (in kHz). Default is NULL.
A numeric vector of length 1 specifying the window length of the spectrogram for applying bandpass. Default
is 10. Ignored if bp = NULL. Note that lower values will increase time resolution, which is more important for signal-to-noise ratio calculations.
Data frame similar to autodetec output, but also includes a new variable
with the signal-to-noise values.
Signal-to-noise ratio (SNR) is a measure of the level of a desired signal compared to
background noise. The function divides the mean amplitude of the signal by
the mean amplitude of the background noise adjacent to the signal.
A general margin to apply before and after the acoustic signal must
be specified. Setting margins for individual signals that have been
previously clipped from larger files may take some optimization, as
for calls within a larger file that are irregularly separated. When
margins overlap with another acoustic signal nearby, the signal-to-noise
ratio (SNR) will be inaccurate. Any SNR less than or equal to one suggests
background noise is equal to or overpowering the acoustic signal.
snrspecs can be used to troubleshoot different noise margins.
# NOT RUN {
{
# First set temporary folder
# setwd(tempdir())
data(list = c("Phae.long1","selec.table"))
writeWave(Phae.long1, "Phae.long1.wav") #save sound files
# specifying the correct margin is important
# use snrspecs to troubleshoot margins for sound files
sig2noise(selec.table[grep("Phae.long1", selec.table$sound.files), ], mar = 0.2)
# this smaller margin doesn't overlap neighboring signals
sig2noise(selec.table[grep("Phae.long1", selec.table$sound.files), ], mar = 0.1)
}
# }
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