R: Finite Impulse Response filter

fir {seewave}

R Documentation

Finite Impulse Response filter

Description

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

Usage

fir(wave, f, channel = 1, from = NULL, to = NULL, bandpass = TRUE, custom = NULL,
wl = 512, wn = "hanning", 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 not `NULL` a band-stop filter is applied between `from` and `to` (by default `NULL`).
`custom`	a vector describing the frequency response of a custom filter. This can be manually generated or obtained with `spec` and `meanspec`. `wl` is no more required. See examples.
`wl`	window length of the impulse filter (even number of points).
`wn`	window name, see `ftwindow` (by default `"hanning"`).
`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"`, `"Sample"`, `"audioSample"` or `"ts"`.

Details

This function is based on the reverse of the Fourier Transform (fft) and on a convolution (convolve) between the wave to be filtered and the impulse filter.

Value

A new wave is returned. The class of the returned object is set with the argument output.

Author(s)

Jerome Sueur

References

Stoddard, P. K. (1998). Application of filters in bioacoustics. In: Hopp, S. L., Owren, M. J. and Evans, C. S. (Eds), Animal acoustic communication. Springer, Berlin, Heidelberg,pp. 105-127.

Examples

a<-noisew(f=8000,d=1)
# low-pass
b<-fir(a,f=8000,to=1500)
spectro(b,f=8000)
# high-pass
c<-fir(a,f=8000,from=2500)
spectro(c,f=8000)
# band-pass
d<-fir(a,f=8000,from=1000,to=2000)
spectro(d,f=8000)
# band-stop
e<-fir(a,f=8000,from=1500,to=2500,bandpass=FALSE)
spectro(e,f=8000)
# custom filter manually generated
myfilter1<-rep(c(rep(0,32),rep(1,32)),4)
g<-fir(a,f=8000,custom=myfilter1)
spectro(g,f=8000)
# custom filter generated using spec()
data(tico)
myfilter2<-spec(tico,f=22050,at=0.7,wl=512,plot=FALSE)
b<-noisew(d=1,f=22050)
h<-fir(b,f=22050,custom=myfilter2)
spectro(h,f=22050)

[Package seewave version 2.1.6 Index]