seewave: ffilter – R documentation

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ffilter

Frequency filter

Description

This function filters out a selected frequency section of a time wave (low-pass, high-pass, low-stop, high-stop, bandpass or bandstop frequency filter).

Usage

ffilter(wave, f, channel = 1, from = NULL, to = NULL, bandpass = TRUE,
custom = NULL, wl = 1024, ovlp = 75, wn = "hanning", fftw = FALSE,
rescale=FALSE, listen=FALSE, output="matrix")

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).
`from`	start frequency (in Hz) where to apply the filter.
`to`	end frequency (in Hz) where to apply the filter.
`bandpass`	if `TRUE` a band-pass filter is applied between `from` and `to`, if `FALSE` a band-stop filter is applied between `from` and `to` (by default `TRUE`).
`custom`	a vector describing the frequency response of a custom filter. This can be manually generated or obtained with `spec` and `meanspec`. The length of the vector should be half the length of `wl`. See examples.
`wl`	window length for the analysis (even number of points).
`ovlp`	overlap between successive FFT windows (in %).
`wn`	window name, see `ftwindow` (by default `"hanning"`).
`fftw`	if `TRUE` calls the function `FFT` of the library `fftw`. See Notes of the `spectro`.
`rescale`	a logical, if `TRUE` then the sample values of new wave (output) are rescaled according to the sample values of `wave` (input).
`listen`	a logical, if `TRUE` the new sound is played back.
`output`	character string, the class of the object to return, either `"matrix"`, `"Wave"`, `"audioSample"` or `"ts"`.

Details

A short-term Fourier transform is first applied to the signal (see spectro), then the frequency filter is applied and the new signal is eventually generated using the reverse of the Fourier Transform (istft).
There is therefore neither temporal modifications nor amplitude modifications.

Value

If plot is FALSE, a new wave is returned. The class of the returned object is set with the argument output.

Author(s)

Jerome Sueur

Examples

a<-noisew(f=8000,d=1)
# low-pass
b<-ffilter(a,f=8000,to=1500)
spectro(b,f=8000,wl=512)
# high-pass
c<-ffilter(a,f=8000,from=2500)
spectro(c,f=8000,wl=512)
# band-pass
d<-ffilter(a,f=8000,from=1000,to=2000)
spectro(d,f=8000,wl=512)
# band-stop
e<-ffilter(a,f=8000,from=1500,to=2500,bandpass=FALSE)
spectro(e,f=8000,wl=512)
# custom
myfilter1<-rep(c(rep(0,64),rep(1,64)),4)
g<-ffilter(a,f=8000,custom=myfilter1)
spectro(g,f=8000)

seewave

Sound Analysis and Synthesis

v2.1.6

GPL (>= 2)

Authors

Jerome Sueur <sueur@mnhn.fr> [cre, au], Thierry Aubin [au], Caroline Simonis [au], Laurent Lellouch [main ctrb], Ethan C. Brown [ctrb], Marion Depraetere [ctrb], Camille Desjonqueres [ctrb], Francois Fabianek [ctrb], Amandine Gasc [ctrb], Eric Kasten [ctrb], Stefanie LaZerte [ctrb], Jonathan Lees [ctrb], Jean Marchal [ctrb], Andre Mikulec [ctrb], Sandrine Pavoine [ctrb], David Pinaud [ctrb], Alicia Stotz [ctrb], Luis J. Villanueva-Rivera [ctrb], Zev Ross [ctrb], Carl G. Witthoft [ctrb], Hristo Zhivomirov [ctrb].

Initial release

2020-06-28