findJumps {soundgen}

Find frequency jumps

Description

This function flags frames with apparent pith jumps (frequency jumps, voice breaks), defined as relatively large and sudden changes in voice pitch or some other frequency measure (peak frequency, a formant frequency, etc). It is called by detectNLP. Algorithm: a frame is considered to contain a frequency jump if the absolute slope at this frame exceeds the average slope over ±jumpWindow around it by more than jumpThres. Note that the slope is considered per second rather than per time step - that is, taking into account the sampling rate of the frequency track. Thus, it's not just the change from frame to frame that defines what is considered a jump, but a change that differs from the trend in the surrounding frames (see examples). If several consecutive frames contain apparent jumps, only the greatest of them is preserved.

Usage

findJumps(
  pitch,
  step,
  jumpThres = 8,
  jumpWindow = 80,
  plot = FALSE,
  xlab = "Time, ms",
  ylab = "f0, Hz",
  ...
)

Arguments

pitch

vector of frequencies per frame, Hz

step

time step between frames, ms

jumpThres

frames in which pitch changes by jumpThres octaves/s more than in the surrounding frames are classified as containing "pitch jumps". Note that this is the rate of frequency change PER SECOND, not from one frame to the next

jumpWindow

the window for calculating the median pitch slope around the analyzed frame, ms

plot

if TRUE, plots the pitch contour with putative frequency jumps marked by arrows

xlab, ylab, ...

graphical parameters passed to plot

Value

Returns a boolean vector of the same length as pitch, where TRUE values correspond to frames with detected pitch jumps.

Examples

pitch = getSmoothContour(anchors = list(
  time = c(0, 350, 351, 890, 891, 1200),
  value = c(140, 230, 460, 330, 220, 200)), len = 40)
step = 25
pj = findJumps(pitch, step, plot = TRUE)

# convert frame indices to time in ms
step = 25
which(pj) * step
# or consider pj's to occur midway between the two frames
which(pj) * step - step / 2

# even very rapid changes are not considered jumps if they match
# the surrounding trend
pitch = getSmoothContour(anchors = list(
  time = c(0, 350, 351, 700),
  value = c(340, 710, 850, 1200)), len = 20)
findJumps(pitch, step, plot = TRUE)
diff(HzToSemitones(pitch)) * (1000 / step) / 12
# the slope at frame 10 (10.4 oct/s) exceeds the jumpThres (8 oct/s), but not
# 10.4 minus the average slope around frame 10 (~3 oct/s, so 10 - 3 < 8)