seewave (version 1.5.5)

spec: 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 = NULL, dBref = NULL,
at = NULL, from = NULL, to = NULL, peaks = NULL,
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

a vector, a matrix (first column), an object of class ts, Sample (left channel), or Wave (left channel).

f

sampling frequency of wave (in Hz). Does not need to be specified if wave is an object of class ts, Sample, or Wave<

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

a character string specifying the type dB to return: "max0" for a maximum dB value at 0, "A", "B", "C" and "D" for common dB weights.

dBref

a dB reference value when dB is not NULL. NULL by default but should be set to 2*10e-5 for a 20 microPa reference (SPL).

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

if not NULL 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.

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
• If peaks is nt NULL, spec returns a list with two elements:
• spec
  the spectrum computed
• of length wl/2,
• peaks
  the peaks value (in kHz).

Details

If at, from or to are FALSE then spec computes the spectrum of the whole signal. peaks setting corresponds to dimension of embed. See examples.

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="max0",col="blue")
spec(tico,f=22050,dB="max0",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")