M {seewave}

Median of the amplitude envelope

Description

This function computes an acoustic index based on the median of the amplitude envelope.

Usage

M(wave, f, channel = 1, envt = "hil", plot = FALSE, ...)

Arguments

wave

an R object.

f

sampling frequency of wave (in Hz). Does not need to be specified if embedded in wave.

channel

channel of the R object, by default left channel (1).

envt

the type of envelope to be used: either "abs" for absolute amplitude envelope or "hil" for Hilbert amplitude envelope. See env.

plot

logical, if TRUE returns a plot of the amplitude envelope of wave (by default FALSE).

...

other env parameters, in particular smoothing parameters. See env.

Details

This amplitude index M is computed according to:

M = \bar{A}(t) \times 2^{1-depth}

with

0 \leq M \leq 1

where A(t) is the amplitude envelope and depth is the signal digitization depth in number of bits.

Value

A numeric vector of length 1 between 0 and 1, without unit.

Author(s)

Jerome Sueur and Marion Depraetere

References

Depraetere M, Pavoine S, Jiguet F, Gasc A, Duvail S, Sueur J (2012) Monitoring animal diversity using acoustic indices: implementation in a temperate woodland. Ecological Indicators, 13, 46-54.

See Also

env, AR

Examples

data(tico)
M(tico)
# smoothing the amplitude may change slightly the result
M(tico, msmooth=c(500,50), plot=TRUE)