seewave (version 1.6.3)

ifreq: Instantaneous frequency

Description

This function returns the instantaneous frequency (and/or phase) of a time wave through the computation of the analytic signal (Hilbert transform).

Usage

ifreq(wave, f, phase = FALSE, threshold = NULL,
plot = TRUE, xlab = "Time (s)", ylab = NULL,
ylim = NULL, type = "l", ...)

Value

• If plot is FALSE, ifreq returns a list of two components:
• p
  a two-column matrix, the first column corresponding to time in seconds (x-axis) and the second column corresponding to wrapped instantaneous phase in radians (y-axis).
• f
  a two-column matrix, the first column corresponding to time in seconds (x-axis) and the second column corresponding to instantaneous frequency in kHz (y-axis).

Details

The instantaneous phase is the argument of the analytic signal obtained throught the Hilbert transform. The instantaneous phase is then unwrapped and derived against time to get the instantaneous frequency. There may be some edge effects at both start and end of the time wave.

References

Mbu Nyamsi, R. G., Aubin, T. & Bremond, J. C. 1994 On the extraction of some time dependent parameters of an acoustic signal by means of the analytic signal concept. Its application to animal sound study. Bioacoustics, 5: 187-203.

See Also

hilbert, zc

Examples

# generate a sound with sine and linear frequency modulations
a<-synth(d=1, f=8000, cf=1500, fm=c(200,10,1000))
# plot on a single graphical device the instantaneous frequency and phase
op<-par(mfrow=c(2,1))
ifreq(a,f=8000,main="Instantaneous frequency")
ifreq(a,f=8000,phase=TRUE,main="Instantaneous phase")
par(op)