soundgen (version 2.7.3)

normalizeFolder: Normalize folder

Description

Normalizes the amplitude of all wav/mp3 files in a folder based on their peak or RMS amplitude or subjective loudness. This is good for playback experiments, which require that all sounds should have similar intensity or loudness.

Usage

normalizeFolder(
  myfolder,
  type = c("peak", "rms", "loudness")[1],
  maxAmp = 0,
  summaryFun = "mean",
  windowLength = 50,
  step = NULL,
  overlap = 70,
  killDC = FALSE,
  windowDC = 200,
  saveAudio = NULL,
  reportEvery = NULL
)

Arguments

myfolder

full path to folder containing input audio files

type

normalize so the output files has the same peak amplitude ('peak'), root mean square amplitude ('rms'), or subjective loudness in sone ('loudness')

maxAmp

maximum amplitude in dB (0 = max possible, -10 = 10 dB below max possible, etc.)

summaryFun

should the output files have the same mean / median / max etc rms amplitude or loudness? (summaryFun has no effect if type = 'peak')

windowLength

length of FFT window, ms (multiple values in a vector produce a multi-resolution spectrogram)

step

you can override overlap by specifying FFT step, ms - a vector of the same length as windowLength (NB: because digital audio is sampled at discrete time intervals of 1/samplingRate, the actual step and thus the time stamps of STFT frames may be slightly different, eg 24.98866 instead of 25.0 ms)

overlap

overlap between successive FFT frames, %

killDC

if TRUE, removed DC offset (see also flatEnv)

windowDC

the window for calculating DC offset, ms

saveAudio

full path to where the normalized files should be saved (defaults to 'myfolder/normalized')

reportEvery

when processing multiple inputs, report estimated time left every ... iterations (NULL = default, NA = don't report)

Details

Algorithm: first all files are rescaled to have the same peak amplitude of maxAmp dB. If type = 'peak', the process ends here. If type = 'rms', there are two additional steps. First the original RMS amplitude of all files is calculated per frame by getRMS. The "quietest" sound with the lowest summary RMS value is not modified, so its peak amplitude remains maxAmp dB. All the remaining sounds are rescaled linearly, so that their summary RMS values becomes the same as that of the "quietest" sound, and their peak amplitudes become smaller, <maxAmp. Finally, if type = 'loudness', the subjective loudness of each sound is estimated by getLoudness, which assumes frequency sensitivity typical of human hearing. The following normalization procedure is similar to that for type = 'rms'.

See Also

getRMS analyze getLoudness

Examples

if (FALSE) {
# put a few short audio files in a folder, eg '~/Downloads/temp'
getRMS('~/Downloads/temp', summaryFun = 'mean')$summary  # different
normalizeFolder('~/Downloads/temp', type = 'rms', summaryFun = 'mean',
  saveAudio = '~/Downloads/temp/normalized')
getRMS('~/Downloads/temp/normalized', summaryFun = 'mean')$summary  # same
# If the saved audio files are treated as stereo with one channel missing,
# try reconverting with ffmpeg (saving is handled by tuneR::writeWave)
}