soundgen (version 3.0.0)

crossFade: Join two waveforms by cross-fading

Description

crossFade joins two input vectors (waveforms) by overlapping and cross-fading them. This is standard for joining two separately generated sounds without audible artifacts.

Usage

crossFade(
  x,
  y,
  crossLen = 15,
  crossLen_points = NULL,
  samplingRate = NULL,
  shape = c("equalPower", "lin", "exp", "log", "cos", "logistic", "gaussian"),
  cutToZC = FALSE,
  steepness = 1,
  SNR = NULL
)

Value

A numeric vector with the original sampling rate. The length is going to be length(x) + length(y) - crossLen_points, or a bit less if cutting to nearest zero crossings.

Arguments

x, y

two numeric vectors (waveforms) to be joined

crossLen

overlap in ms

crossLen_points

overlap in points (overrides crossLen)

samplingRate

the sampling rate of input vectors, Hz (needed only if crossLen is given in ms rather than points)

shape

controls the type of fade function: 'equalPower' = equal power (default), 'lin' = linear, 'exp' = exponential, 'log' = logarithmic, 'cos' = cosine, 'logistic' = logistic S-curve, 'gaussian' = Gaussian curve

cutToZC

if TRUE, input vectors are truncated so that x ends with a zero crossing and y starts with a zero crossing, both on an upward portion of the soundwave

steepness

scaling factor regulating the steepness of fading curves (except for shapes 'lin' and 'cos'): 0 = linear, >1 = steeper than default

SNR

if a number, the two sounds are normalized so that the RMS amplitude of x is SNR dB above that of y (NULL = no normalization; negative values make x quieter than y)

See Also

fade

Examples

sound1 = sin(1:100 / 9)
sound2 = sin(7:106 / 3)
plot(c(sound1, sound2), type = 'b')
# an ugly discontinuity at 100 that will make an audible click

sound = crossFade(sound1, sound2, crossLen_points = 25)
plot(sound, type = 'b') # a nice, smooth transition
length(sound) # but note that cross-fading costs us crossLen_points = 25
# points even without cutting to zc, and much more if we trim to
# zero crossings and then overlap

sound = crossFade(sound1, sound2, crossLen_points = 25,
  SNR = 6)  # make sound1 6 dB louder (RMS) than sound2
plot(sound, type = 'b') # a nice, smooth transition

# Actual sounds, alternative shapes of fade-in/out
sound3 = soundgen(formants = 'a', pitch = 200, sylLen = 300,
                  addSilence = 0, attackLen = c(50, 0))
sound4 = soundgen(formants = 'u', pitch = 200, sylLen = 300,
                  addSilence = 0, attackLen = c(0, 50))

# simple concatenation (with a click)
cf1 = c(sound3, sound4)
osc(cf1, 16000, from = .25, to = .35)
# playme(cf1, 16000)

# concatenation from zc to zc (no click, but a rough transition)
cf2 = crossFade(sound3, sound4, crossLen_points = 0, cutToZC = TRUE)
osc(cf2, 16000, from = .25, to = .35)
# playme(cf2, 16000)

# crossFade over 35 ms - brief, but smooth
cf3 = crossFade(sound3, sound4, crossLen = 35, samplingRate = 16000)
osc(cf3, 16000, from = .25, to = .35)
# playme(cf3, 16000)

# equal-power cross-fade over 300 ms (shortens the sound by ~300 ms)
cf4 = crossFade(sound3, sound4, samplingRate = 16000,
                 crossLen = 300, shape = 'equalPower')
osc(cf4, 16000)
# playme(cf4, 16000)