addAM: Add amplitude modulation

In soundgen: Sound Synthesis and Acoustic Analysis

Add amplitude modulation

Description

Adds sinusoidal or logistic amplitude modulation to a sound. Sinusoidal AM creates a single pair of sidebands at ±amFreq around each original harmonic, whereas non-sinusoidal AM creates broader sidebands with more extra harmonics (see examples).

Usage

addAM(
  x,
  samplingRate = NULL,
  amDep = 25,
  amFreq = 30,
  amType = c("logistic", "sine"),
  amShape = 0,
  invalidArgAction = c("adjust", "abort", "ignore"),
  play = FALSE,
  saveAudio = FALSE,
  plot = FALSE,
  savePlots = FALSE,
  embed = FALSE,
  reportEvery = NULL,
  cores = 1,
  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)
amDep	amplitude modulation (AM) depth, %. 0: no change; 100: AM with amplitude range equal to the dynamic range of the sound (anchor format)
amFreq	AM frequency, Hz (anchor format)
amType	"logistic" = logistic (default), "sine" = sinusoidal
amShape	ignored if amType = "sine", otherwise determines the shape of non-sinusoidal AM: 0 = ~sine, -1 = notches, +1 = clicks (anchor format)
invalidArgAction	what to do if an argument is invalid or outside the permitted range: 'adjust' = reset to default value, 'abort' = stop execution, 'ignore' = throw a warning and continue (may crash)
play	if TRUE, plays the output audio using the default player on your system. If a character string, it is passed to playme as the name of the player to use (e.g. 'aplay', 'play', 'vlc'). In case of errors, try setting another default player for playme
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, produces a plot of the results
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
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
width, height, units, res	graphical parameters for saving plots passed to png

Value

Returns the modified audio as a numeric vector with the original sampling rate.

Examples

sound1 = soundgen(pitch = c(200, 300), addSilence = 0)
s1 = addAM(sound1, 16000, amDep = c(0, 50, 0), amFreq = 75, plot = TRUE)
# playme(s1)
## Not run: 
# Parameters can be specified as in the soundgen() function, eg:
s2 = addAM(sound1, 16000,
         amDep = list(time = c(0, 50, 52, 200, 201, 300),
                      value = c(0, 0, 35, 25, 0, 0)),
         plot = TRUE, play = TRUE)

# Sinusoidal AM produces exactly 2 extra harmonics at ±amFreq
# around each f0 harmonic (amFreq, and thus the width of sidebands,
# may vary over time):
s3 = addAM(sound1, 16000, amDep = 30, amFreq = c(50, 80),
           amType = 'sine', plot = TRUE, play = TRUE)
spectrogram(s3, 16000, windowLength = 150, ylim = c(0, 2))

# Non-sinusoidal AM produces multiple new harmonics,
# which can resemble subharmonics...
s4 = addAM(sound1, 16000, amDep = 70, amFreq = 50, amShape = -1,
           plot = TRUE, play = TRUE)
spectrogram(s4, 16000, windowLength = 150, ylim = c(0, 2))

# ...but more often look like sidebands
sound3 = soundgen(sylLen = 600, pitch = c(800, 1300, 1100), addSilence = 0)
s5 = addAM(sound3, 16000, amDep = c(0, 30, 100, 40, 0),
           amFreq = 105, amShape = -.3,
           plot = TRUE, play = TRUE)
spectrogram(s5, 16000, ylim = c(0, 5))

# Feel free to add AM stochastically:
s6 = addAM(sound1, 16000,
           amDep = rnorm(10, 40, 20), amFreq = rnorm(20, 70, 20),
           plot = TRUE, play = TRUE)
spectrogram(s6, 16000, windowLength = 150, ylim = c(0, 2))

# If amFreq is locked to an integer ratio of f0, we can get subharmonics
# For ex., here is with pitch 400-600-400 Hz (soundgen interpolates pitch
# on a log scale and amFreq on a linear scale, so we align them by extracting
# a long contour on a log scale for both)
con = soundgen:::getSmoothContour(anchors = c(400, 600, 400),
                       len = 20, thisIsPitch = TRUE)
s = soundgen(sylLen = 1500, pitch = con, amFreq = con/3, amDep = 30,
             plot = TRUE, play = TRUE, ylim = c(0, 3))

# Process all files in a folder and save the modified audio
addAM('~/Downloads/temp', saveAudio = TRUE, amFreq = 70, amDep = c(0, 50))

## End(Not run)

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