flatEnv: Flat envelope / compressor

In soundgen: Sound Synthesis and Acoustic Analysis

Flat envelope / compressor

Description

Applies a compressor - that is, flattens the amplitude envelope of a waveform, reducing the difference in amplitude between loud and quiet sections. This is achieved by dividing the waveform by some function of its smoothed amplitude envelope (Hilbert, peak or root mean square).

Usage

flatEnv(
  x,
  samplingRate = NULL,
  scale = NULL,
  compression = 1,
  method = c("hil", "rms", "peak"),
  windowLength = 50,
  killDC = FALSE,
  dynamicRange = 40,
  reportEvery = NULL,
  cores = 1,
  saveAudio = FALSE,
  plot = FALSE,
  savePlots = FALSE,
  embed = FALSE,
  col = "blue",
  width = 900,
  height = 500,
  units = "px",
  res = NA,
  ...
)

compressor(
  x,
  samplingRate = NULL,
  scale = NULL,
  compression = 1,
  method = c("hil", "rms", "peak"),
  windowLength = 50,
  killDC = FALSE,
  dynamicRange = 40,
  reportEvery = NULL,
  cores = 1,
  saveAudio = FALSE,
  plot = FALSE,
  savePlots = FALSE,
  embed = FALSE,
  col = "blue",
  width = 900,
  height = 500,
  units = "px",
  res = NA,
  ...
)

Arguments

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
samplingRate	sampling rate of x (only needed if x is a numeric vector)
scale	maximum possible amplitude of input, used to normalize the input vector (only needed if x is a numeric vector)
compression	the amount of compression to apply: 0 = none, 1 = maximum
method	hil = Hilbert envelope, rms = root mean square amplitude, peak = peak amplitude per window
windowLength	the length of smoothing window, ms
killDC	if TRUE, dynamically removes DC offset or similar deviations of average waveform from zero (see examples)
dynamicRange	parts of sound quieter than -dynamicRange dB will not be amplified
reportEvery	when processing multiple inputs, report estimated time left every reportEvery iterations (NULL = default, NA = don't report); see reportTime
cores	number of cores for parallel processing
saveAudio	if TRUE, saves the processed audio in a subdirectory named after the function and created in the input directory (if input is a file or folder) or in the working directory
plot	if TRUE, plots the original sound, the smoothed envelope, and the compressed sound
savePlots	if TRUE, creates a subdirectory in the input directory (if input is a file or folder) or in the working directory (if input is a vector etc), named after the function (eg "spectrogram/"). All plots and audio files (if any) are saved in this new directory. If there are multiple inputs, an html notebook is also created for easy viewing and listening
embed	if TRUE and savePlots is set and there are multiple inputs, all saved images and audio (if any) are embedded in the exported html notebook for easy sharing; if FALSE, the html file links to separate images and audio files (but separate files are still saved). NB: for this to work, package "base64enc" must be installed
col	the color of amplitude contours
width, height, units, res	graphical parameters for saving plots passed to png
...	other graphical parameters passed to points() that control the appearance of amplitude contours, eg lwd, lty, etc.

Value

If the input is a single audio (file, Wave, or numeric vector), returns the compressed waveform as a numeric vector with the original sampling rate and scale. If the input is a folder with several audio files, returns a list of compressed waveforms, one for each file.

See Also

transplantEnv

Examples

a = rnorm(500) * seq(1, 0, length.out = 500)
b = flatEnv(a, 1000, plot = TRUE, windowLength = 5)    # too short
c = flatEnv(a, 1000, plot = TRUE, windowLength = 450)  # too long
d = flatEnv(a, 1000, plot = TRUE, windowLength = 100)  # about right

## Not run: 
s = soundgen(sylLen = 1000, ampl = c(0, -40, 0), plot = TRUE)
# playme(s)
s_flat1 = flatEnv(s, 16000, dynamicRange = 60, plot = TRUE,
                  windowLength = 50, method = 'hil')
s_flat2 = flatEnv(s, 16000, dynamicRange = 60, plot = TRUE,
                  windowLength = 10, method = 'rms')
s_flat3 = flatEnv(s, 16000, dynamicRange = 60, plot = TRUE,
                  windowLength = 10, method = 'peak')
# playme(s_flat2)

# Remove DC offset
s1 = c(rep(0, 50), runif(1000, -1, 1), rep(0, 50)) +
     seq(.3, 1, length.out = 1100)
s2 = flatEnv(s1, 16000, plot = TRUE, windowLength = 50, killDC = FALSE)
s3 = flatEnv(s1, 16000, plot = TRUE, windowLength = 50, killDC = TRUE)

# Compress and save all audio files in a folder
s4 = flatEnv('~/Downloads/temp',
             method = 'peak', compression = .5,
             saveAudio = TRUE,
             savePlots = TRUE,
             col = 'green', lwd = 5)
osc(s4[[1]])

## End(Not run)

soundgen documentation built on Sept. 20, 2026, 5:07 p.m.