The Zwicker method for calculating the loudness of stationary and time-varying sounds is standardized in ISO 532-1 [1]. In SQAT, the implementation of this loudness model is named Loudness_ISO532_1 (see code here). For the purpose of validating a specific implementation, the ISO standard provides a set of 25 test signals and the following requirements:
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Criteria for stationary loudness: for all stationary test signals given in the Annex B.2 and B.3, the specific loudness values shall differ by no more than
$\pm5~\%$ or$\pm0.1~\mathrm{sone/Bark}$ from the reference values, and the total loudness shall not deviate from the reference values by more than$\pm5~\%$ or$\pm0.1~\mathrm{sone}$ . -
Criteria for time-varying loudness: for all test signals given in the Annex B.4, the specific loudness vs. time shall not differ by more than
$\pm5~\%$ or$\pm0.1~\mathrm{sone/Bark}$ from the reference values within a temporal tolerance of$\pm2~\mathrm{ms}$ . The tolerance can be extended to$\pm10~\%$ or$\pm0.2~\mathrm{sone/Bark}$ within a temporal tolerance of$\pm2~\mathrm{ms}$ , but only for maximum$1~\%$ of the sampled specific loudness vs. time function using a time resolution of$\pm2~\mathrm{ms}$ . -
Criteria for time-varying loudness: for all test signals given in the Annex B.4 and B.5, the deviation of the total loudness vs. time shall differ by no more than
$\pm5~\%$ or$\pm0.1~\mathrm{sone}$ from the reference values within a temporal tolerance of$\pm2~\mathrm{ms}$ . The tolerance can be extended to$\pm10~\%$ or$\pm0.2~\mathrm{sone}$ within a temporal tolerance of$\pm2~\mathrm{ms}$ , but only for maximum$1~\%$ of the sampled total loudness vs. time function using a time resolution of$\pm2~\mathrm{ms}$ .
The dataset of test sounds provided by the ISO standard is freely available and can be downloaded from the following link: http://standards.iso.org/iso/532/-1/ed-1/en. In this folder, the verification of the Loudness_ISO532_1 implementation in SQAT using the test signals from the ISO standard is presented.
- Stationary loudness: synthetic signals provided in Annex B.2 and B.3
- Time-varying loudness: synthetic signals provided in Annex B.4
- Time-varying loudness: technical signals provided in Annex B.5
[1] International Organization for Standardization. (2017). Acoustics - Methods for calculating loudness - Part 1: Zwicker method (ISO Standard No. 532-1).