loudness_zwst_perseg

loudness_zwst_perseg(signal, fs, nperseg=4096, noverlap=None, field_type='free')

Compute the loudness value per segments from a time signal

This function computes the acoustic loudness according to Zwicker method (ISO.532-1:2017) by segmentation of a stationary signal.

Parameters:

• signal (array_like) – Input time signal in [Pa].

• fs (float, optional) – Sampling frequency, can be omitted if the input is a DataTimeobject. Default to None

• nperseg (int, optional) – Length of each segment. Defaults to 4096.

• noverlap (int, optional) – Number of points to overlap between segments. If None, noverlap = nperseg / 2. Defaults to None.

• field_type ({'free', 'diffuse'}) – Type of soundfield. Default is ‘free’

Returns:

• N (float) – Overall loudness [sones], size (Ntime,).

• N_specific (numpy.ndarray) – Specific loudness [sones/bark], size (Nbark, Ntime).

• bark_axis (numpy.ndarray) – Bark axis, size (Nbark,).

• time_axis (numpy.ndarray) – Time axis, size (Ntime,).

Warning

Nnumpy.array

The overall loudness array [sones], size (Ntime,).

N_specificnumpy.ndarray

The specific loudness array [sones/bark], size (Nbark, Ntime).

bark_axis: numpy.array

The Bark axis array, size (Nbark,).

time_axis: numpy.array

The time axis array, size (Ntime,). The sampling frequency of the signal must be >= 48 kHz to fulfill requirements.

If the provided signal doesn’t meet the requirements, it will be resampled.

See also

loudness_zwst

Loudness computation for a stationary time signal

loudness_zwst_freq

Loudness computation from a sound spectrum

loudness_zwtv

Loudness computation for a non-stationary time signal

Notes

For each considered segment, the total loudness \(N\) is computed as the integral of the specific loudness \(N'\) measured in sone/bark, over the Bark scale. The values of specific loudness are evaluated from third octave band levels as function of critical band rate \(z\) in Bark.

\[N=\int_{0}^{24Bark}N'(z)\textup{dz}\]

Due to normative continuity, the method is in accordance with ISO 226:1987 equal loudness contours instead of ISO 226:2003, as defined in the following standards:

• ISO 532:1975 (method B)

• DIN 45631:1991

• ISO 532-1:2017 (method 1)

References

[1]

E.Zwicker and H.Fastl. Program for calculating loudness according to din 45631 (iso 532b). Journal of the Acoustical Society of Japan, 1991. URL: https://www.jstage.jst.go.jp/article/ast1980/12/1/12_1_39/_article.

[2]

ISO.532-1:2017. Methods for calculating loudness, part 1 Zwicker Method. International Organization for Standardization, 2017. URL: https://www.iso.org/standard/63077.html.

Examples

>>> from mosqito.sq_metrics import loudness_zwst_perseg
>>> import matplotlib.pyplot as plt
>>> import numpy as np
>>> fs=48000
>>> d=1
>>> dB=60
>>> time = np.arange(0, d, 1/fs)
>>> f = np.linspace(1000,5000, len(time))
>>> stimulus = 0.5 * (1 + np.sin(2 * np.pi * f * time))
>>> rms = np.sqrt(np.mean(np.power(stimulus, 2)))
>>> ampl = 0.00002 * np.power(10, dB / 20) / rms
>>> stimulus = stimulus * ampl
>>> N, N_spec, bark_axis, time_axis = loudness_zwst_perseg(stimulus, fs=fs)
>>> plt.plot(time_axis, N)
>>> plt.xlabel("Time [s]")
>>> plt.ylabel("Loudness [Sone]")

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