R: Difference between two frequency spectra

diffspec {seewave}

R Documentation

Difference between two frequency spectra

Description

This function estimates the surface difference between two frequency spectra.

Usage

diffspec(spec1, spec2, f = NULL, mel = FALSE,
plot = FALSE, type="l", 
lty=c(1, 2), col =c(2, 4, 8),
flab = NULL, alab = "Amplitude",
flim = NULL, alim = NULL, title = TRUE, legend = TRUE, ...)

Arguments

`spec1`	a first data set resulting of a spectral analysis obtained with `spec` or `meanspec` (not in dB). This can be either a two-column matrix (col1 = frequency, col2 = amplitude) or a vector (amplitude).
`spec2`	a first data set resulting of a spectral analysis obtained with `spec` or `meanspec` (not in dB). This can be either a two-column matrix (col1 = frequency, col2 = amplitude) or a vector (amplitude).
`f`	sampling frequency of waves used to obtain `spec1` and `spec2` (in Hz). Not necessary if `spec1` and/or `spec2` is a two-column matrix obtained with `spec` or `meanspec`.
`mel`	a logical, if `TRUE` the (htk-)mel scale is used.
`plot`	logical, if `TRUE` plots both spectra and their surface difference (by default `FALSE`).
`type`	if `plot` is `TRUE`, type of plot that should be drawn. See `plot` for details (by default "l" for lines).
`lty`	a vector of length 2 for the line type of `spec1` and `spec2` if `type`="l".
`col`	a vector of length 3 for the colour of `spec1`, `spec2`, and the surface difference between each of them.
`flab`	title of the frequency axis.
`alab`	title of the amplitude axis.
`flim`	the range of frequency values.
`alim`	range of amplitude axis.
`title`	logical, if `TRUE`, adds a title with D value.
`legend`	logical, if `TRUE` adds a legend to the plot.
`...`	other `plot` graphical parameters.

Details

D is a Manhattan distance (l1 norm).
Both spectra are first transformed as probability mass functions (PMF).
Spectral difference is then computed according to:

D = sum(abs(spec1-spec2))/2

, with 0 < D < 1.

Value

The difference is returned. This value is without unit. When plot is TRUE, both spectra and their difference surface are plotted on the same graph.

Note

This method can be used as a relative distance estimation between different spectra.
The dB value obtained can be very different from the one visually estimated when looking at the graph (plot=TRUE).

Author(s)

Jerome Sueur, Sandrine Pavoine and Laurent Lellouch

References

Sueur, J., Pavoine, S., Hamerlynck, O. and Duvail, S. (2008). Rapid acoustic survey for biodiversity appraisal. PLoS One, 3(12): e4065.

Examples

a <- noisew(f=8000,d=1)
b <- synth(f=8000,d=1,cf=2000)
c <- synth(f=8000,d=1,cf=1000)
d <- noisew(f=8000,d=1)
speca <- spec(a,f=8000,wl=512,at=0.5,plot=FALSE)
specb <- spec(b,f=8000,wl=512,at=0.5,plot=FALSE)
specc <- spec(c,f=8000,wl=512,at=0.5,plot=FALSE)
specd <- spec(d,f=8000,wl=512,at=0.5,plot=FALSE)
diffspec(speca,speca,f=8000)
#[1] 0 => similar spectra of course !
diffspec(speca,specb)
diffspec(speca,specc,plot=TRUE)
diffspec(specb,specc,plot=TRUE)
diffspec(speca,specd,plot=TRUE)
## mel scale
require(tuneR)
data(orni)
data(tico)
orni.mel <- melfcc(orni, nbands = 256, dcttype = "t3", fbtype = "htkmel", spec_out=TRUE)
orni.mel.mean <- apply(orni.mel$aspectrum, MARGIN=2, FUN=mean)
tico.mel <- melfcc(tico, nbands = 256, dcttype = "t3", fbtype = "htkmel", spec_out=TRUE)
tico.mel.mean <- apply(tico.mel$aspectrum, MARGIN=2, FUN=mean)
diffspec(orni.mel.mean, tico.mel.mean, f=22050, mel=TRUE, plot=TRUE)

[Package seewave version 2.1.6 Index]