View source: R/shiftFormants.R
shiftFormants  R Documentation 
Raises or lowers formants (resonance frequencies), changing the voice quality
or timbre of the sound without changing its pitch, statically or dynamically.
Note that this is only possible when the fundamental frequency f0 is lower
than the formant frequencies. For best results, freqWindow
should be
no lower than f0 and no higher than formant bandwidths. Obviously, this is
impossible for many signals, so just try a few reasonable values, like ~200
Hz for speech. If freqWindow
is not specified, soundgen sets it to the
average detected f0, which is slow.
shiftFormants( x, multFormants, samplingRate = NULL, freqWindow = NULL, dynamicRange = 80, windowLength = 50, step = NULL, overlap = 75, wn = "gaussian", interpol = c("approx", "spline")[1], normalize = c("max", "orig", "none")[2], play = FALSE, saveAudio = NULL, reportEvery = NULL, cores = 1, ... )
x 
path to a folder, one or more wav or mp3 files c('file1.wav', 'file2.mp3'), Wave object, numeric vector, or a list of Wave objects or numeric vectors 
multFormants 
1 = no change, >1 = raise formants (eg 1.1 = 10% up, 2 =
one octave up), <1 = lower formants. Anchor format accepted (see

samplingRate 
sampling rate of 
freqWindow 
the width of spectral smoothing window, Hz. Defaults to detected f0 
dynamicRange 
dynamic range, dB. All values more than one dynamicRange under maximum are treated as zero 
windowLength 
length of FFT window, ms 
step 
you can override 
overlap 
overlap between successive FFT frames, % 
wn 
window type accepted by 
interpol 
the method for interpolating scaled spectra 
normalize 
"orig" = same as input (default), "max" = maximum possible peak amplitude, "none" = no normalization 
play 
if TRUE, plays the synthesized sound using the default player on
your system. If character, passed to 
saveAudio 
full path to the folder in which to save audio files (one per detected syllable) 
reportEvery 
when processing multiple inputs, report estimated time left every ... iterations (NULL = default, NA = don't report) 
cores 
number of cores for parallel processing 
... 
other graphical parameters 
Algorithm: phase vocoder. In the frequency domain, we separate the complex
spectrum of each STFT frame into two parts. The "receiver" is the flattened
or smoothed complex spectrum, where smoothing is achieved by obtaining a
smoothed magnitude envelope (the amount of smoothing is controlled by
freqWindow
) and then dividing the complex spectrum by this envelope.
This basically removes the formants from the signal. The second component,
"donor", is a scaled and interpolated version of the same smoothed magnitude
envelope as above  these are the formants shifted up or down. Warping can be
easily implemented instead of simple scaling if nonlinear spectral
transformations are required. We then multiply the "receiver" and "donor"
spectrograms and reconstruct the audio with iSTFT.
shiftPitch
transplantFormants
s = soundgen(sylLen = 200, ampl = c(0,10), pitch = c(250, 350), rolloff = c(9, 15), noise = 40, formants = 'aii', addSilence = 50) # playme(s) s1 = shiftFormants(s, samplingRate = 16000, multFormants = 1.25, freqWindow = 200) # playme(s1) ## Not run: data(sheep, package = 'seewave') # import a recording from seewave playme(sheep) spectrogram(sheep) # Lower formants by 4 semitones or ~20% = 2 ^ (4 / 12) sheep1 = shiftFormants(sheep, multFormants = 2 ^ (4 / 12), freqWindow = 150) playme(sheep1, sheep@samp.rate) spectrogram(sheep1, sheep@samp.rate) orig = seewave::meanspec(sheep, wl = 128, plot = FALSE) shifted = seewave::meanspec(sheep1, wl = 128, f = sheep@samp.rate, plot = FALSE) plot(orig[, 1], log(orig[, 2]), type = 'l') points(shifted[, 1], log(shifted[, 2]), type = 'l', col = 'blue') # dynamic change: raise formants at the beginning, lower at the end sheep2 = shiftFormants(sheep, multFormants = c(1.3, .7), freqWindow = 150) playme(sheep2, sheep@samp.rate) spectrogram(sheep2, sheep@samp.rate) ## End(Not run)
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