seewave (version 2.2.3)

fir: 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")

Value

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

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".

Author

Jerome Sueur

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.

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.

See Also

ffilter, bwfilter, preemphasis, lfs, afilter

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)