seewave (version 1.7.0)

spectro3D: 3D-spectrogram of a time wave

Description

This function returns a three-dimension spectrographic representation of a time wave. The function corresponds to short-term Fourier transform.

Usage

spectro3D(wave, f, wl = 512, wn = "hanning", zp = 0,
ovlp = 0, norm = TRUE, fftw = FALSE, dB = "max0", dBref = NULL, plot = TRUE,
magt = 10, magf = 10, maga = 2,
palette = rev.terrain.colors)

Value

• This function returns a list of three items:
• time
  a numeric vector corresponding to the time axis.
• freq
  a numeric vector corresponding to the frequency axis.
• amp
  a numeric matrix corresponding to the amplitude values. Each column is a Fourier transform of length wl/2.

Details

Following Heisenberg uncertainty principle, the short-term Fourier transform cannot be precised in both time and frequency. The temporal and frequency precisions of the function are actually dependent of the wl value. Choosing a high wl value will increase the frequency resolution but reduce the temporal one, and vice versa. The frequency precision is obtained by calculating the ratio f/wl, and the temporal precision is obtained by calculating the reverse ratio wl/f. This problem can be reduced in some way with zp that adds 0 values on both sides of the analysis window. This increases frequency resolution without altering time resolution. Any colour palette can be used. In particular, it is possible to use other palettes coming with seewave: rev.gray.colors.1, rev.gray.colors.2, spectro.colors, temp.colors, rev.heat.colors, rev.cm.colors, rev.topo.colors, corresponding to the reverse of heat.colors,topo.colors, cm.colors. Use magt, magf and maga to resize the plot.

See Also

spectro, dynspec, wf, fft.

Examples

require(rgl)
data(tico)
spectro3D(tico,f=22050,wl=512,ovlp=75,zp=16,maga=4,palette=rev.terrain.colors)
# linear amplitude scale without a normisation of the STFT matrix
# time and frequency scales need to be dramatically amplified
spectro3D(tico, norm=FALSE, dB=NULL, magt=100000, magf=100000)