getLoudness: Get loudness

Description

Estimates subjective loudness per frame, in sone. Based on EMBSD speech quality measure, particularly the matlab code in Yang (1999) and Timoney et al. (2004). Note that there are many ways to estimate loudness and many other factors, ignored by this model, that could influence subjectively experienced loudness. Please treat the output with a healthy dose of skepticism! Also note that the absolute value of calculated loudness critically depends on the chosen "measured" sound pressure level (SPL). getLoudness estimates how loud a sound will be experienced if it is played back at an SPL of SPL_measured dB. The most meaningful way to use the output is to compare the loudness of several sounds analyzed with identical settings or of different segments within the same recording.

Usage

getLoudness(x, samplingRate = NULL, scale = NULL, windowLength = 50,
  step = NULL, overlap = 50, SPL_measured = 70, Pref = 2e-05,
  spreadSpectrum = TRUE, plot = TRUE, mar = c(5.1, 4.1, 4.1, 4.1),
  ...)

Arguments

path to a .wav or .mp3 file or a vector of amplitudes with specified samplingRate

samplingRate

sampling rate of x (only needed if x is a numeric vector, rather than an audio file), must be > 2000 Hz

scale

the maximum possible value of x (only needed if x is a numeric vector, rather than an audio file); defaults to observed max(abs(x)) if it is greater than 1 and to 1 otherwise

windowLength

length of FFT window, ms

step

you can override overlap by specifying FFT step, ms

overlap

overlap between successive FFT frames, %

SPL_measured

sound pressure level at which the sound is presented, dB

Pref

reference pressure, Pa

spreadSpectrum

if TRUE, applies a spreading function to account for frequency masking

plot

should a spectrogram be plotted? TRUE / FALSE

mar

margins of the spectrogram

...

other plotting parameters passed to spectrogram

Value

Returns a list of length two:

specSone: spectrum in sone: a matrix with frequency on the bark scale in rows and time (STFT frames) in columns
loudness: a vector of loudness per STFT frame (sone)

Details

Algorithm: calibrates the sound to the desired SPL (Timoney et al., 2004), extracts a spectrogram, converts to bark scale (audspec), spreads the spectrum to account for frequency masking across the critical bands (Yang, 1999), converts dB to phon by using standard equal loudness curves (ISO 226), converts phon to sone (Timoney et al., 2004), sums across all critical bands, and applies a correction coefficient to standardize output. Calibrated so as to return a loudness of 1 sone for a 1 kHz pure tone with SPL of 40 dB.

References

ISO 226 as implemented by Jeff Tackett (2005) on https://www.mathworks.com/matlabcentral/fileexchange/ 7028-iso-226-equal-loudness-level-contour-signal
Timoney, J., Lysaght, T., Schoenwiesner, M., & MacManus, L. (2004). Implementing loudness models in matlab.
Yang, W. (1999). Enhanced Modified Bark Spectral Distortion (EMBSD): An Objective Speech Quality Measure Based on Audible Distortion and Cognitive Model. Temple University.

Examples

Run this code

# NOT RUN {
sounds = list(
  white_noise = runif(8000, -1, 1),
  white_noise2 = runif(8000, -1, 1) / 2,  # ~6 dB quieter
  pure_tone_1KHz = sin(2*pi*1000/16000*(1:8000))  # pure tone at 1 kHz
)
loud = rep(0, length(sounds)); names(loud) = names(sounds)
for (i in 1:length(sounds)) {
  # playme(sounds[[i]], 16000)
  l = getLoudness(
    x = sounds[[i]], samplingRate = 16000, scale = 1,
    windowLength = 20, step = NULL,
    overlap = 50, SPL_measured = 40,
    Pref = 2e-5, plot = FALSE)
  loud[i] = mean(l$loudness)
}
loud
# white noise (sound 1) is twice as loud as pure tone at 1 KHz (sound 3),
# and note that the same white noise with lower amplitude has lower loudness
# (provided that "scale" is specified)
# compare: lapply(sounds, range)

# }
# NOT RUN {
  s = soundgen()
  l = getLoudness(s, SPL_measured = 70,
                  samplingRate = 16000, plot = TRUE, osc = TRUE)
  # The estimated loudness in sone depends on target SPL
  l = getLoudness(s, SPL_measured = 40,
                  samplingRate = 16000, plot = TRUE)

  # ...but not (much) on windowLength and samplingRate
  l = getLoudness(soundgen(), SPL_measured = 40, windowLength = 50,
                  samplingRate = 16000, plot = TRUE)

  # input can be an audio file
  getLoudness('~/Downloads/temp/032_ut_anger_30-m-roar-curse.wav')
# }

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