ama {seewave} | R Documentation |
This function computes the Fourier analysis of a time wave envelope. This allows to detect periodicity, in particular those generated by amplitude modulations.
ama(wave, f, envt = "hil", wl = 512, plot = TRUE, type = "l", ...)
wave |
a vector , a matrix (first column),
an object of class ts , Sample (left channel),
or Wave (left channel). |
f |
sampling frequency of wave (in Hz).
Does not need to be specified if wave is an object of class ts ,
Sample , or Wave . |
envt |
the type of envelope to be used: either "abs" for absolute amplitude envelope or "hil" for Hilbert amplitude envelope. |
wl |
length of the window for the analysis (even number of points, by default = 512). |
plot |
logical, if TRUE the spectrum of the envelope
(by default TRUE ). |
type |
if plot is TRUE , type of plot that should be drawn.
See plot for details (by default "l" for lines). |
... |
other meanspec parameters. |
This function is based on env
and meanspec
.
The envelope of wave
is first computed and the spectrum of this envelope
is then processed. All env
and meanspec
arguments can be
set up. Be sure to set up wl
large enough if you want to detect low amplitude
modulation periodicity.
If plot
is FALSE
, ama
returns a numeric
vector corresponding to the computed spectrum.
If peaks
is not NULL
, ama
returns a list with
two elements:
spec |
the spectrum computed |
peaks |
the peaks values (in kHz). |
Jerome Sueur sueur@mnhn.fr
data(orni) # detection of 2 main amplitude modulations in a cicada song: # one with a 0.020 kHz frequency (due to signal/silence periodicity) # one with a 0.258 kHz frequency (due to pulses in the echemes) # one with a 2.369 kHz frequency (fundamental frequency) ama(orni,f=22050,wl=1024) # these amplitude modulations can be identify with a cursor: ama(orni,f=22050,wl=1024,identify=TRUE)