R: Resonance quality factor of a frequency spectrum

Q {seewave}

R Documentation

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, mel = FALSE, plot = TRUE, colval = "red",
cexval = 1, fontval = 1, flab = NULL,
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 = amplitude) or a vector (amplitude).
`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).
`mel`	a logical, if `TRUE` the (htk-)mel scale is used.
`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.

Details

A high Q value indicates a highly resonant system.

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)

Note

This function is based on an linear interpolation of the spectrum so that the result should be considered as an estimation, not an exact measure.

Author(s)

Jerome Sueur, improved by Laurent Lellouch

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)

[Package seewave version 2.1.6 Index]