spec {seewave}R Documentation

Frequency spectrum of a time wave

Description

This function returns the frequency spectrum (i.e. the relative amplitude of the frequency content) of a time wave. Results can be obtained either as absolute or dB data.

Usage

spec(wave, f, wl = 512, wn = "hanning", PSD = FALSE,
PMF = FALSE, dB = FALSE,
at = NULL, from = NULL, to = NULL, peaks = FALSE,
identify = FALSE, col = "black", cex = 1, colpeaks = "red",
cexpeaks = 1, fontpeaks = 1, plot = 1, flab = "Frequency (kHz)",
alab = "Amplitude", flim = c(0, f/2000),
alim = NULL, type="l",...)

Arguments

wave data describing a time wave or a Sample object generated loading a wav file with loadSample (package sound).
f sampling frequency of wave (in Hz). Does not need to be specified if wave is a Sample object.
wl if at is not null, length of the window for the analysis (even number of points, by defaults = 512).
wn window name, see ftwindow (by default "hanning").
PSD if TRUE return Power Spectra Density, i. e. the square of the spectra.
PMF if TRUE return Probability Mass Function, i. e. the probability distribution of frequencie.
dB logical, if TRUE returns the spectrum in dB (by default FALSE).
at position where to compute the spectrum (in s).
from start mark where to compute the spectrum (in s).
to end mark where to compute the spectrum (in s).
peaks returns peaks value for a given span (see details).
identify to identify frequency and amplitude values on the plot with the help of a cursor.
col colour of the spectrum.
cex pitch size of the spectrum.
colpeaks colour of peaks value plotted on the spectrum.
cexpeaks character size of peaks value plotted on the spectrum.
fontpeaks font of peaks value plotted on the spectrum.
plot if 1 returns frequency on x-axis, if 2 returns frequency on y-axis, (by default 1).
flab title of the frequency axis.
alab title of the amplitude axis.
flim range of frequency axis.
alim range of amplitude axis.
type if plot is TRUE, type of plot that should be drawn. See plot for details (by default "l" for lines).
... other plot graphical parameters.

Details

If at, from or to are FALSE then spec computes the spectrum of the whole signal.
peaks setting corresponds to dimension of embed.
When using identify, press ‘stop’ tools bar button to return values in the console.

Value

This function returns a two-column matrix, the first column corresponding to the frequency axis, the second column corresponding to the amplitude axis.
If identify is TRUE, spec returns a list with two elements:

freq the frequency of the points chosen on the spectrum
amp the relative amplitude of the points chosen on the spectrum
spec the spectrum computed
peaks the peaks value (in kHz).

Note

This function is based on fft.

Author(s)

Jerome Sueur sueur@mnhn.fr and Martin Maechler maechler@stat.math.ethz.ch for peaks.

See Also

meanspec, dynspec, corspec, fft.

Examples

data(tico)
# spectrum of the whole signal, in absolute or dB amplitude,
# horizontaly or vertically
op<-par(mfrow=c(2,2))
spec(tico,f=22050)
spec(tico,f=22050,col="red",plot=2)
spec(tico,f=22050,dB=TRUE,col="blue")
spec(tico,f=22050,dB=TRUE,col="green",plot=2)
par(op)
# spectra computed at specific locations with peak value
op<-par(mfrow=c(2,2))
spec(tico,f=22050,wl=512,at=0.2,peak=175)
title("Note A")
spec(tico,f=22050,wl=512,at=0.7,peak=175)
title("Note B")
spec(tico,f=22050,wl=512,at=1.1,peak=175)
title("Note C")
spec(tico,f=22050,wl=512,at=1.6,peak=165)
title("Note D")
par(op)
# an indirect way to compare spectra 
a<-spec(tico,f=22050,wl=512,at=0.2,plot=FALSE)
b<-spec(tico,f=22050,wl=512,at=0.7,plot=FALSE)
c<-spec(tico,f=22050,wl=512,at=1.1,plot=FALSE)
d<-spec(tico,f=22050,wl=512,at=1.6,plot=FALSE)
all<-cbind(a[,2],b[,2],c[,2],d[,2])
matplot(x=a[,1],y=all,yaxt="n",
    xlab="Frequency (kHz)",ylab="Amplitude",xaxs="i",type="l")
legend(8,0.8,c("Note A","Note B", "Note C", "Note D"),bty="o",
    lty=c(1:4),col=c(1:4))
# spectrum from a particular position to another one
op<-par(mfrow=c(2,1))
oscillo(tico,f=22050)
abline(v=c(0.5,0.9),col="red",lty=2)
text(c("from 0.5 s","to 0.7 s"),
    x=c(0.5,0.9),y=rep(max(tico/1.1),2),col="red",pos=4)
spec(tico,f=22050,wl=512,from=0.5,to=0.9,col="red")
title("Spectrum of the note B")
par(op)
# spectrum and spectrogram
data(orni)
orni1<-cutw(orni,f=22050,from=0.32,to=0.39)
layout(matrix(c(1,2),nc=2),widths=c(3,1))
par(mar=c(5,4,3,0.5))
spectro(orni1,f=22050,wl=128,zp=8,ovlp=85,scale=FALSE)
par(mar=c(5,1,3,0.5))
spec(orni1,f=22050,col="red",plot=2,flab="",yaxt="n")

[Package seewave version 1.5.0 Index]