soundgen (version 1.5.0)

getSpectralEnvelope: Spectral envelope

Description

Prepares a spectral envelope for filtering a sound to add formants, lip radiation, and some stochastic component regulated by temperature. Formants are specified as a list containing time, frequency, amplitude, and width values for each formant (see examples). See vignette('sound_generation', package = 'soundgen') for more information.

Usage

getSpectralEnvelope(nr, nc, formants = NA, formantDep = 1,
  formantWidth = 1, lipRad = 6, noseRad = 4, mouth = NA,
  interpol = c("approx", "spline", "loess")[3], mouthOpenThres = 0.2,
  openMouthBoost = 0, vocalTract = NULL, temperature = 0.05,
  formDrift = 0.3, formDisp = 0.2, formantDepStoch = 20,
  smoothLinearFactor = 1, samplingRate = 16000, speedSound = 35400,
  plot = FALSE, duration = NULL, colorTheme = c("bw", "seewave",
  "...")[1], nCols = 100, xlab = "Time", ylab = "Frequency, kHz",
  ...)

Arguments

nr

the number of frequency bins = windowLength_points/2, where windowLength_points is the size of window for Fourier transform

nc

the number of time steps for Fourier transform

formants

a character string like "aaui" referring to default presets for speaker "M1"; a vector of formant frequencies; or a list of formant times, frequencies, amplitudes, and bandwidths, with a single value of each for static or multiple values of each for moving formants. formants = NA defaults to schwa. Time stamps for formants and mouthOpening can be specified in ms or an any other arbitrary scale.

formantDep

scale factor of formant amplitude (1 = no change relative to amplitudes in formants)

formantWidth

= scale factor of formant bandwidth (1 = no change)

lipRad

the effect of lip radiation on source spectrum, dB/oct (the default of +6 dB/oct produces a high-frequency boost when the mouth is open)

noseRad

the effect of radiation through the nose on source spectrum, dB/oct (the alternative to lipRad when the mouth is closed)

mouth

mouth opening (0 to 1, 0.5 = neutral, i.e. no modification) (anchor format)

interpol

the method of smoothing envelopes based on provided mouth anchors: 'approx' = linear interpolation, 'spline' = cubic spline, 'loess' (default) = polynomial local smoothing function. NB: this does NOT affect the smoothing of formant anchors

mouthOpenThres

open the lips (switch from nose radiation to lip radiation) when the mouth is open >mouthOpenThres, 0 to 1

openMouthBoost

amplify the voice when the mouth is open by openMouthBoost dB

vocalTract

the length of vocal tract, cm. Used for calculating formant dispersion (for adding extra formants) and formant transitions as the mouth opens and closes. If NULL or NA, the length is estimated based on specified formant frequencies (if any)

temperature

hyperparameter for regulating the amount of stochasticity in sound generation

formDrift

scale factor regulating the effect of temperature on the depth of random drift of all formants (user-defined and stochastic): the higher, the more formants drift at a given temperature

formDisp

scale factor regulating the effect of temperature on the irregularity of the dispersion of stochastic formants: the higher, the more unevenly stochastic formants are spaced at a given temperature

formantDepStoch

the amplitude of additional formants added above the highest specified formant (only if temperature > 0)

smoothLinearFactor

regulates smoothing of formant anchors (0 to +Inf) as they are upsampled to the number of fft steps nc. This is necessary because the input formants normally contains fewer sets of formant values than the number of fft steps. smoothLinearFactor = 0: close to default spline; >3: approaches linear extrapolation

samplingRate

sampling frequency, Hz

speedSound

speed of sound in warm air, cm/s. Stevens (2000) "Acoustic phonetics", p. 138

plot

if TRUE, produces a plot of the spectral envelope

duration

duration of the sound, ms (for plotting purposes only)

colorTheme

black and white ('bw'), as in seewave package ('seewave'), or another color theme (e.g. 'heat.colors')

nCols

number of colors in the palette

xlab, ylab

labels of axes

...

other graphical parameters passed on to image()

Value

Returns a spectral filter (matrix nr x nc, where nr is the number of frequency bins and nc is the number of time steps). Accordingly, rownames of the output give central frequency of each bin(in kHz), while colnames give time values (in ms if duration is specified, otherwise 0 to 1).

Examples

# NOT RUN {
# [a] with F1-F3 visible
e = getSpectralEnvelope(nr = 512, nc = 50, duration = 300,
  formants = soundgen:::convertStringToFormants('a'),
  temperature = 0, plot = TRUE)
# image(t(e))  # to plot the output on a linear scale instead of dB

# some "wiggling" of specified formants plus extra formants on top
e = getSpectralEnvelope(nr = 512, nc = 50,
  formants = soundgen:::convertStringToFormants('a'),
  temperature = 0.1, formantDepStoch = 20, plot = TRUE)

# a schwa based on the length of vocal tract = 15.5 cm
e = getSpectralEnvelope(nr = 512, nc = 50, formants = NA,
  temperature = .1, vocalTract = 15.5, plot = TRUE)

# no formants at all, only lip radiation
e = getSpectralEnvelope(nr = 512, nc = 50,
  formants = NA, temperature = 0, plot = TRUE)

# mouth opening
e = getSpectralEnvelope(nr = 512, nc = 50,
  vocalTract = 16, plot = TRUE, lipRad = 6, noseRad = 4,
  mouth = data.frame(time = c(0, .5, 1), value = c(0, 0, .5)))

# scale formant amplitude and/or bandwidth
e = getSpectralEnvelope(nr = 512, nc = 50,
  formants = soundgen:::convertStringToFormants('a'),
  formantWidth = 2, formantDep = .5,
  temperature = 0, plot = TRUE)

# manual specification of formants
e = getSpectralEnvelope(nr = 512, nc = 50, plot = TRUE, samplingRate = 16000,
  formants = list(f1 = data.frame(time = c(0, 1), freq = c(900, 500),
                                  amp = 20, width = c(80, 50)),
                  f2 = data.frame(time = c(0, 1), freq = c(1200, 2500),
                                  amp = 20, width = 100),
                  f3 = data.frame(time = 0, freq = 2900,
                                  amp = 20, width = 120)))
# }

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