seewave (version 1.7.6)

Q: Resonance quality factor of a frequency spectrum

Description

This function estimates the frequency pureness of a time wave by returning the resonant quality factor Q at a specific dB level.

Usage

Q(spec, f = NULL, level = -3, plot = TRUE, colval = "red",
cexval = 1, fontval = 1, flab = "Frequency (kHz)",
alab = "Relative amplitude (dB)", type = "l", ...)

Arguments

spec

a data set resulting of a spectral analysis obtained with spec, or meanspec (in dB). This can be either a two-column matrix (col1 = frequency, col2 = a

f

sampling frequency of the wave used to obtain spec (in Hz). Not necessary if spec is a two columns matrix obtained with spec or meanspec

level

frequency bandwidth set by an amplitude value relative to spectrum (in dB).

plot

logical, if TRUE returns the spectrum with Q plotted (by default TRUE).

colval

colour of plotting Q.

cexval

character size of plotting Q.

fontval

font of plotting Q.

flab

title of the frequency axis.

alab

title of the 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

• A list is returned with the following four items:
• Q
  a numeric vector of length 1 returning the Q factor (no units)
• dfreq
  a numeric vector of length 1 the dominant frequency (kHz)
• fmin
  a numeric vector of length 1 returning the minimum frequency of the -dB level bandwidth (kHz)
• fmax
  a numeric vector of length 1 returning the minimum frequency of the -dB level bandwidth (kHz)
• bwd
  a numeric vector of length 1 returning the bandwidth, i. e. fmax-fmin (kHz)

Details

A high Q value indicates a highly resonant system.

See Also

spec, meanspec, corspec, fft.

Examples

# bird song
data(tico)
t<-spec(tico,f=22050,at=1.1,plot=FALSE,dB="max0")
op<-par(mfrow=c(2,1),las=1)
Q(t,type="l")
Q(t,type="l",xlim=c(3.8,4.2),ylim=c(-60,0))
title("zoom in")
par(op)
# cricket, changing the dB level
data(pellucens)
p<-spec(pellucens,f=11025,at=0.5,plot=FALSE,dB="max0")
op<-par(mfrow=c(3,1))
Q(p,type="l",xlim=c(1.8,2.6),ylim=c(-70,0))
title("level = - 3 (default value)",col.main="red")
Q(p,type="l",level=-6,
    xlim=c(1.8,2.6),ylim=c(-70,0),colval="blue")
title("level = - 6",col.main="blue")
Q(p,type="l",level=-9,
    xlim=c(1.8,2.6),ylim=c(-70,0),colval="green")
title("level = - 9",col.main="green")
par(op)