diffenv: Difference between two amplitude envelopes

In seewave: Sound Analysis and Synthesis

Difference between two amplitude envelopes

Description

This function estimates the surface difference between two amplitude envelopes.

Usage

diffenv(wave1, wave2, f, channel = c(1,1), envt = "hil", msmooth = NULL, ksmooth = NULL,
plot = FALSE, lty1 = 1, lty2 = 2, col1 = 2, col2 = 4, cold = 8,
xlab = "Time (s)", ylab = "Amplitude", ylim = NULL, legend = TRUE, ...)

Arguments

wave1	a first R object.
wave2	a second R object.
f	sampling frequency of wave (in Hz). Does not need to be specified if embedded in wave.
channel	channel of the R objects, by default left channel (1) for each object.
envt	the type of envelope to be used: either "abs" for absolute amplitude envelope or "hil" for Hilbert amplitude envelope. See env.
msmooth	a vector of length 2 to smooth the amplitude envelope with a mean sliding window. The first component is the window length (in number of points). The second component is the overlap between successive windows (in %). See env.
ksmooth	kernel smooth via kernel. See env.
plot	logical, if TRUE plots both envelopes and their surface difference (by default FALSE).
lty1	line type of the first envelope (envelope of wave1).
lty2	line type of the second envelope (envelope of wave2).
col1	colour of the first envelope (envelope of wave1).
col2	colour of the second envelope (envelope of wave2).
cold	colour of the surface difference.
xlab	title of the time axis.
ylab	title of the amplitude axis.
ylim	range of amplitude axis.
legend	logical, if TRUE adds a legend to the plot.
...	other plot graphical parameters.

Details

D is a Manhattan distance (l1 norm).
Envelopes of both waves are first transformed as probability mass functions (PMF).
Envelope difference is then computed according to:

D = \frac{\sum{|env1-env2|}}{2}, with D \in [0,1].

Value

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

Note

This method can be used as a relative distance estimation between different envelopes.

Author(s)

Jerome Sueur [e-mail].

References

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

See Also

env, corenv, diffspec, diffwave

Examples

data(tico) ; tico <- tico@left
data(orni) ; orni <- orni@left
# selection in tico of two waves with similar duration
tico2<-tico[1:length(orni)]
diffenv(tico2,orni,f=22050,plot=TRUE)
# smoothing the envelope gives a better graph but slightly changes the result
diffenv(tico2,orni,f=22050,msmooth=c(20,0),plot=TRUE)

seewave documentation built on Oct. 19, 2023, 5:07 p.m.