seewave (version 1.0)

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 = FALSE, PSD = FALSE, dB = FALSE,
at = FALSE, from = FALSE, to = FALSE, 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,...)

Arguments

wave

data describing a time wave.

f

sampling frequency of wave.

wl

if at is not null, length of the window for the analysis (even number of points).

PSD

if TRUE return Power Spectra Density, i. e. the square of the spectra.

dB

logical, if TRUE return 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 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

the range of frequency values.

alim

range of amplitude axis.

...

other plot graphical parameters.

Value

• This function returns a vector of numeric data corresponding to the computed spectrum. If peaks is TRUE, spec returns a list with two elements:
• spec
  the spectrum computed
• peaks
  the peaks value (in kHz).

Details

A Hanning function is applied to the analysis window. 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.

See Also

meanspec, 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,type="l")
spec(tico,f=22050,type="l",col="red",plot=2)
spec(tico,f=22050,type="l",dB=TRUE,col="blue")
spec(tico,f=22050,type="l",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,type="l",peak=175)
title("Note A")
spec(tico,f=22050,wl=512,at=0.7,type="l",peak=175)
title("Note B")
spec(tico,f=22050,wl=512,at=1.1,type="l",peak=175)
title("Note C")
spec(tico,f=22050,wl=512,at=1.6,type="l",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,b,c,d)
matplot(x=seq(0,11.025,length.out=nrow(all)),y=all,type="l",yaxt="n",
    xlab="Frequency (kHz)",ylab="Amplitude",xaxs="i")
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,type="l",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,type="l",col="red",plot=2,flab="",yaxt="n")