| combfilter {seewave} | R Documentation |
This function processes a feedforward comb filter and plots a spectrogram of the filtered wave asso- ciated with the frequency response of the filter.
combfilter(wave, f, channel = 1, alpha, K, units = c("samples", "seconds"),
plot = FALSE, output = "matrix", ...)
wave |
an |
f |
sampling frequency (in Hz). Does not need to be specified if
embedded in |
channel |
channel of the R object, by default left channel (1). |
alpha |
a numeric vector of length 1 for the scaling factor. See Details. |
K |
a numeric vector of lenght 1 for the delay length, in
|
units |
units in which |
plot |
a logical, if |
output |
character string, the class of the object to return,
either |
... |
other arguments to be passed to |
A comb filter consists in adding a delayed version of a signal to itself resulting in constructive and destructive interference. The feedforward version of a comb filter can be written following:
y(n) = x(n) + alpha * x(n - K)
where alpha is the scaling factor and K the delay length. The frequency response of the filter is obtained with:
H(f) = sqrt((1+alpha^2)+2*cos(omega*K))
The frequency response is periodic. The depth of the cycles is controlled with alpha and the number of cycles with K.
A new wave is returned. The class of the returned object is set with the argument output.
Setting K to high values may generate unwanted results.
The feedback form of the combfilter is not implemented yet.
Jerome Sueur
combfilter, fir, squarefilter, drawfilter, ffilter, bwfilter
## Not run: f <- 44100 ## chirp s1 <- synth(f=f, cf=1, d=2, fm=c(0,0,f/2,0,0), out="Wave") combfilter(s1, alpha=1, K=50, plot=TRUE) ## harmonic sound s2 <- synth(f=f, d=2, cf=600, harmonics=rep(1, 35), output="Wave") combfilter(s2, alpha=1, K=10, plot=TRUE) ## noise, units in seconds s3 <- noisew(d=2, f=44100, out="Wave") combfilter(s3, alpha=0.5, K=1e-4, units="seconds", plot=TRUE) ## End(Not run)