writeAMWave: Write Amplitude Modulated Waveform

In PAMmisc: Miscellaneous Functions for Passive Acoustic Analysis

Write Amplitude Modulated Waveform

Description

Write a wave file for a synthesized amplitude modulated call

Usage

writeAMWave(
  fileName,
  outDir,
  signalLength,
  modFrequency,
  frequency,
  sampleRate,
  window = c(0.55, 0.45),
  silence = c(0, 0),
  gainFactor = 0.1
)

createAMWave(
  signalLength,
  modFrequency,
  frequency,
  sampleRate,
  window = c(0.55, 0.45),
  silence = c(0, 0),
  gainFactor = 0.1
)

Arguments

fileName	name of the file to write. If missing, the file be named usign signalLength, modFrequency, frequency, and sampleRate
outDir	directory to write wave files to
signalLength	length of signal to create in seconds
modFrequency	modulation frequency in Hz of the amplitude modulation
frequency	frequency of the AM call
sampleRate	sample rate for the wave file to create
window	window constants for applying the amplitude modulation. See details.
silence	silence to pad before and after signal in seconds
gainFactor	scaling factor between 0 and 1. Low numbers are recommended (default 0.1)

Details

Amplitude modulated signals are modelled as an ideal sinusoid multiplied by a window function. The window function is an offset sinusoid with frequency equal to the modulation frequency:

W = .5 + .45 * sin(2 \pi mf t)

See example(writeAMWave) for a plot showing how this works.

Value

writeAMWave invisibly returns the file name, createAMWave returns a Wave class object

Author(s)

Taiki Sakai [e-mail]

Examples

# Visualisation of modelled AM wave
signal <- sin(2*pi*100*(1:1000)/1000)
window <- .55 + .45 * sin(2*pi*15*(1:1000)/1000)
oldMf <- par()$mfrow
par(mfrow=c(3,1))
plot(signal, type='l')
plot(window, type='l')
plot(window*signal, type='l')
tmpFile <- file.path(tempdir(), 'tempWav.wav')
writeAMWave(tmpFile, signalLength = 1, modFrequency = 1000,
               frequency = 30000, sampleRate = 100000)
file.remove(tmpFile)
amWave <- createAMWave(signalLength = 1, modFrequency = 1000,
                             frequency = 30e3, sampleRate = 100e3)
par(mfrow=oldMf)

PAMmisc documentation built on June 22, 2024, 9:37 a.m.