signal_to_noise_ratio {baRulho}R Documentation

Measure attenuation as signal-to-noise ratio

Description

signal_to_noise_ratio measures attenuation as signal-to-noise ratio of signals referenced in an extended selection table.

Usage

signal_to_noise_ratio(X, mar, parallel = 1, pb = TRUE, eq.dur = FALSE,
noise.ref = "adjacent", type = 1, bp = 'freq.range', 
output = "est", hop.size = 1, wl = NULL)

Arguments

X

object of class 'extended_selection_table' created by the function selection_table from the warbleR package.

mar

numeric vector of length 1. Specifies the margins adjacent to the start and end points of selection over which to measure ambient noise.

parallel

Numeric vector of length 1. Controls whether parallel computing is applied by specifying the number of cores to be used. Default is 1 (i.e. no parallel computing).

pb

Logical argument to control if progress bar is shown. Default is TRUE.

eq.dur

Logical. Controls whether the ambient noise segment that is measured has the same duration to that of the signal (if TRUE. Default is FALSE). If TRUE then 'mar' and 'noise.ref' arguments are ignored.

noise.ref

Character vector of length 1 to determined which noise segment must be used for measuring ambient noise. Two options are available:

  • adjacent: measure ambient noise right before the signal (using argument 'mar' to define duration of ambient noise segments).

  • custom: measure ambient noise segments referenced in the selection table (labeled as 'ambient' in the 'signal.type' column). Those segments will be used to apply the same ambient noise reference to all signals in a sound file. Therefore, at least one 'ambient' selection for each sound file must be provided. If several 'ambient' selections by sound file are supplied, then the root mean square of the amplitude envelope will be averaged across those selections.

type

Numeric vector of length 1. Selects the formula to be used to calculate the signal-to-noise ratio (S = signal , N = background noise):

  • 1: ratio of S amplitude envelope root mean square to N amplitude envelope root mean square (rms(env(S))/rms(env(N))) as described by Darden (2008).

  • 2: ratio of the difference between S amplitude envelope root mean square and N amplitude envelope root mean square to N amplitude envelope root mean square ((rms(env(S)) - rms(env(N)))/rms(env(N)), as described by Dabelsteen et al (1993).

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' (default), which will make the function use the 'bottom.freq' and 'top.freq' as the bandpass range.

output

Character vector of length 1 to determine if an extended selection table ('est', default) or a data frame ('data.frame').

hop.size

A numeric vector of length 1 specifying the time window duration (in ms). Default is 1 ms, which is equivalent to ~45 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. Ignored if bp = NULL. If supplied, 'hop.size' is ignored. Note that lower values will increase time resolution, which is more important for amplitude ratio calculations.

Details

Signal-to-noise ratio (SNR) measures signal amplitude level in relation to ambient noise. A general margin in which ambient noise will be measured must be specified. Alternatively, a selection of ambient noise can be used as reference (see 'noise.ref' argument). When margins overlap with another acoustic signal nearby, SNR will be inaccurate, so margin length should be carefully considered. Any SNR less than or equal to one suggests background noise is equal to or overpowering the acoustic signal. The function will measure signal-to-noise ratio within the supplied frequency range (e.g. bandpass) of the reference signal ('bottom.freq' and 'top.freq' columns in 'X') by default (that is, when bp = 'freq.range'.

Value

Extended selection table similar to input data, but also includes a new column (signal.to.noise.ratio) with the signal-to-noise ratio values.

Author(s)

Marcelo Araya-Salas (marcelo.araya@ucr.ac.cr)

References

Araya-Salas, M. (2020). baRulho: baRulho: quantifying habitat-induced degradation of (animal) acoustic signals in R. R package version 1.0.2

Dabelsteen, T., Larsen, O. N., & Pedersen, S. B. (1993). Habitat-induced degradation of sound signals: Quantifying the effects of communication sounds and bird location on blur ratio, excess attenuation, and signal-to-noise ratio in blackbird song. The Journal of the Acoustical Society of America, 93(4), 2206.

Darden, SK, Pedersen SB, Larsen ON, & Dabelsteen T. (2008). Sound transmission at ground level in a short-grass prairie habitat and its implications for long-range communication in the swift fox *Vulpes velox*. The Journal of the Acoustical Society of America, 124(2), 758-766.

See Also

excess_attenuation

Examples

{
# load example data
data("playback_est")

# using measure ambient noise reference selections 
signal_to_noise_ratio(X = playback_est, mar = 0.05, noise.ref = 'custom')

# remove ambient selections
playback_est <- playback_est[playback_est$signal.type != "ambient", ]

# using margin for ambient noise of 0.05 and adjacent measure ambient noise reference
signal_to_noise_ratio(X = playback_est, mar = 0.05, noise.ref = 'adjacent')

}


[Package baRulho version 1.0.5 Index]