ISO 226 loudness countours (pydsm.iso226)
Loudness contours from ISO 226.
Contours are returned both as tables of data and as contour functions
Functions returning ISO 226 contours
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Generates an equal loudness contour as described in ISO 226. |
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Generates an interpolation of an equal loudness contour. |
Functions computing loudness/acoustic pressure
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Table of sound pressure levels for given loudness in ISO 226. |
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Table of perceived loudness levels for given sound pressure in ISO 226. |
Functions returning data tabled in the standard
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Table of frequencies in ISO 226. |
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Table of exponents for loudness perception in ISO 226. |
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Table of magnitudes of the linear transfer function in ISO 226. |
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Table of thresholds of hearing in ISO 226. |
Notes
This module uses data from the latest revision of ISO 226 [1]. For reference, also consider [2].
The ISO standard provides the equal loudness contours as tabled data. Tables end at 12.5 kHz. Above this frequency equal-loudness-level data are relatively scarce and tend to be variable [3]. Yet, it is known that the human ear has a precipitous decline in sensitivity with increasing frequency above 15 kHz, to the point that at about 20 kHz the percieved sound becomes negligible (> 100 dB attenuation) [4]. For this reason, this module includes the possibility of delivering some modified ISO contours where the tabled data is augmented by creating a new data point at 20 kHz where the behavior found at 20 Hz is replicated.
ISO 226:2003 “Acoustics - Normal equal-loudness-level contours”
Jeff Tackett, “ISO 226 Equal-Loudness-Level Contour Signal,” 2005 (https://www.mathworks.com/matlabcentral/fileexchange/7028)
Yoiti Suzuki et al, “Precise and Full-range Determination of Two-dimensional Equal Loudness Contours,” 2003 (http://www.mp3-tech.org/programmer/docs/IS-01Y-E.pdf)
Robert A. Wannamaker “Psychoacoustically Optimal Noise Shaping”, J. Audio Eng. Soc., Vol. 40, N. 7/8, 1992 July/August