NDSI {seewave}

Normalized Difference Soundscape Index

Description

This function computes the Normalized Difference Soundscape Index as described by Kasten et al. (2012).

Usage

NDSI(x, anthropophony = 1, biophony = 2:8, max = FALSE)

Arguments

x

a two-column numeric matrix computed with soundscapespec.

anthropophony

a numeric vector defining the frequency band(s) of the anthropophony (in kHz).

biophony

a numeric vector defining the frequency band(s) of the biophony (in kHz).

max

a logical, if TRUE then defines the biophony as the maximum - not the sum - of the 2 and 8 kHz frequency bands

Details

NDSI aims at estimating the level of anthropogenic disturbance on the soundscape by computing the ratio of human-generated (anthropophony) to biological (biophony) acoustic components found in field collected sound samples. In terms of frequency, the anthropophony is defined as the [1-2[ kHz frequency bin and the biophony as the [2-8[ kHz frequency bins of a soundscape frequency spectrum (see soundscapespec).

NDSI is computed according to:

NDSI = \frac{(biophony - anthropophony)}{(biophony + anthropophony)}

NDSI varies between -1 and +1, where +1 indicates a signal containing no anthropophony.

Value

A numeric vector of length 1 giving the NDSI value.

Author(s)

Jerome Sueur

References

Kasten, E.P., Gage, S.H., Fox, J. & Joo, W. (2012). The remote environmental assessment laboratory's acoustic library: an archive for studying soundscape ecology. Ecological Informatics, 12, 50-67.

See Also

soundscapespec, SAX, NDSI

Examples

## Note that 'tico' is not a soundscape recording...
data(tico)
spec <- soundscapespec(tico, plot=FALSE)
NDSI(spec)
NDSI(spec, max=TRUE)