ISO 226 loudness countours (pysdm.iso226)
Loudness contours from ISO 226.
Contours are returned both as tables of data and as contour functions
Functions returning ISO 226 contours
| iso226_spl_contour([L_N, hfe]) |
Generates an equal loudness contour as described in ISO 226. |
| iso226_spl_itpl([L_N, hfe, k]) |
Generates an interpolation of an equal loudness contour. |
Functions computing loudness/acoustic pressure
| tabled_L_p(L_N[, hfe]) |
Table of sound pressure levels for given loudness in ISO 226. |
| tabled_L_N(L_p[, hfe]) |
Table of perceived loudness levels for given sound pressure in ISO 226. |
Functions returning data tabled in the standard
| tabled_f([hfe]) |
Table of frequencies in ISO 226. |
| tabled_alpha_f([hfe]) |
Table of exponents for loudness perception in ISO 226. |
| tabled_L_U([hfe]) |
Table of magnitudes of the linear transfer function in ISO 226. |
| tabled_T_f([hfe]) |
Table of thresholds of hearing in ISO 226. |
Notes
This module uses data from the latest revision of ISO 226 [R19].
For reference, also consider [R20].
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 [R21]. 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) [R22]. 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.
| [R19] | ISO 226:2003 “Acoustics - Normal equal-loudness-level contours” |
| [R22] | Robert A. Wannamaker “Psychoacoustically Optimal Noise
Shaping”, J. Audio Eng. Soc., Vol. 40, N. 7/8, 1992 July/August |
