# sottek-hearing-model

> Part of [LISQM](https://zhenxianli.github.io/LISQM/) (List of Implementations of Sound Quality Metrics), a list of open-source implementations of psychoacoustic metrics. Data as of 2026-10-28. Web page: https://zhenxianli.github.io/LISQM/projects/sottek-hearing-model.html

Python implementation of the ECMA-418-2:2025 (4th edition) Sottek Hearing Model metrics: loudness and roughness (with binaural combination), tonality (per channel), and fluctuation strength on the main branch. Translated from the MATLAB code used in SQAT and the RefMap project.

- **Repository:** https://github.com/mlotinga/sottek-hearing-model
- **Language:** Python
- **Kind:** Library/Toolbox (Functions to call from your own code: a Python package, a MATLAB toolbox, or a C, C++, C#, Rust or Julia library.)
- **Group:** established (Described in a publication, used by others, or written by the authors of the model, with more than a year of history. A very good implementation.)
- **Licence:** GPL-3.0-only — The LICENSE file has always been GPL-3.0 and the project metadata was changed to GPL-3.0-only on 2026-08-31; the metadata of the current PyPI release (0.1.14) still says AGPL-3.0-only.
- **Package:** PyPI `sottek-hearing-model` (https://pypi.org/project/sottek-hearing-model/)
- **Install:** `pip install sottek-hearing-model`
- **Latest release:** v0.1.14 (2026-03)
- **Last commit:** 2026-09-18 (active)
- **GitHub stars:** 23
- **Maintainers:** Mike Lotinga
- **AI assistance:** not stated
- **Paper:** Lotinga, M. J. B., Torjussen, M., & Felix Greco, G. (2025). Verified implementations of the Sottek psychoacoustic Hearing Model standardised sound quality metrics (ECMA-418-2 loudness, tonality and roughness). *Forum Acusticum / Euronoise 2025*, Málaga. https://doi.org/10.61782/fa.2025.0951
- **How to cite:** The README asks for the paper above, which published the MATLAB code the package was translated from, and gives a BibTeX entry for it. Name the version or commit you used.
- **Entry checked:** 2026-10-08

## What it implements

| Metric | Edition | Functions | Status | Validation (as stated) | Notes |
|---|---|---|---|---|---|
| [Sottek Hearing Model loudness](https://zhenxianli.github.io/LISQM/metrics/loudness-ecma-418-2.html) | [ECMA-418-2:2025 (4th ed.)](https://ecma-international.org/wp-content/uploads/ECMA-418-2_4th_edition_june_2025.pdf) (mono or stereo, with combined binaural output; since 0.1.9) | `shm_loudness_ecma`, `shm_loudness_ecma_from_comp` | available | standard or paper data (calibration signals and one recording); also compared with ArtemiS SUITE (HEAD acoustics) | — |
| [Sottek Hearing Model roughness](https://zhenxianli.github.io/LISQM/metrics/roughness-ecma-418-2.html) | [ECMA-418-2:2025 (4th ed.)](https://ecma-international.org/wp-content/uploads/ECMA-418-2_4th_edition_june_2025.pdf) (with combined binaural output; since 0.1.9) | `shm_roughness_ecma` | available | standard or paper data (reference signal and one recording); also compared with ArtemiS SUITE (HEAD acoustics) | — |
| [Sottek Hearing Model fluctuation strength](https://zhenxianli.github.io/LISQM/metrics/fluctuation-strength-ecma-418-2.html) | [ECMA-418-2:2025 (4th ed.)](https://ecma-international.org/wp-content/uploads/ECMA-418-2_4th_edition_june_2025.pdf) (needs at least 1.37 s of signal; binaural option) | `shm_fluctuation_ecma` | unreleased | compared with refmap-psychoacoustics (its source) and ArtemiS SUITE (HEAD acoustics) | Merged on 2026-09-18. Five departures from the printed text are documented (four equations and one interpretation of Section 9.1.8). |
| [Sottek Hearing Model tonality](https://zhenxianli.github.io/LISQM/metrics/tonality-ecma-418-2.html) | [ECMA-418-2:2025 (4th ed.)](https://ecma-international.org/wp-content/uploads/ECMA-418-2_4th_edition_june_2025.pdf) (since 0.1.9) | `shm_tonality_ecma` | available | standard or paper data (reference signal and one recording); also compared with ArtemiS SUITE (HEAD acoustics) | Optional experimental tonal-annoyance weighting (Sottek & Becker, 2019) since 0.1.14. |

## How it was validated

As reported by the project; LISQM has not run the code. Two implementations that agree can still share the same error.

**Checked by the maintainer of LISQM:** In personal use, Zhenxian LI found its results in very good agreement with those of HEAD acoustics ArtemiS SUITE. This is a personal check, not a published comparison.

- [Sottek Hearing Model loudness](https://zhenxianli.github.io/LISQM/metrics/loudness-ecma-418-2.html), ECMA-418-2:2025 (4th ed.): standard or paper data (calibration signals and one recording); also compared with ArtemiS SUITE (HEAD acoustics)
  - Ported or adapted from [refmap-psychoacoustics](https://zhenxianli.github.io/LISQM/projects/refmap-psychoacoustics.html) (the author's own code).
  - Unit tests check the standard's calibration signals (1 kHz, 40 dB gives 1 sone_HMS).
  - RefMap's verification compared the Python code, before it became this package, and the MATLAB original with HEAD acoustics ArtemiS v17.1 for the two calibration signals and a 30 s binaural street recording.
- [Sottek Hearing Model roughness](https://zhenxianli.github.io/LISQM/metrics/roughness-ecma-418-2.html), ECMA-418-2:2025 (4th ed.): standard or paper data (reference signal and one recording); also compared with ArtemiS SUITE (HEAD acoustics)
  - Ported or adapted from [refmap-psychoacoustics](https://zhenxianli.github.io/LISQM/projects/refmap-psychoacoustics.html) (the author's own code).
  - Unit tests check the standard's reference signal, which should give 1 asper_HMS, at 48 and 44.1 kHz.
  - RefMap's verification against ArtemiS v17.1, as for loudness.
- [Sottek Hearing Model fluctuation strength](https://zhenxianli.github.io/LISQM/metrics/fluctuation-strength-ecma-418-2.html), ECMA-418-2:2025 (4th ed.): compared with [refmap-psychoacoustics](https://zhenxianli.github.io/LISQM/projects/refmap-psychoacoustics.html) (its source) and ArtemiS SUITE (HEAD acoustics)
  - Ported or adapted from [refmap-psychoacoustics](https://zhenxianli.github.io/LISQM/projects/refmap-psychoacoustics.html) (the author's own code). It was compared with the code it was ported from, which checks the port only.
  - A draft report (18 September 2026) compares it with `acousticSHMFluctuation.m`, the MATLAB code it was translated from: equal to floating-point precision on the synthetic signals and on one channel of each recording, with a small difference in a short time window on the other channel.
  - Against HEAD acoustics ArtemiS SUITE v17: 0.994 against 1.003 vacil_HMS for the calibration signal (the standard's target is 1.0), −8 % to +12 % for the overall values of three binaural recordings, and correlations of 0.91 to 0.998 for the time-dependent values.
- [Sottek Hearing Model tonality](https://zhenxianli.github.io/LISQM/metrics/tonality-ecma-418-2.html), ECMA-418-2:2025 (4th ed.): standard or paper data (reference signal and one recording); also compared with ArtemiS SUITE (HEAD acoustics)
  - Ported or adapted from [refmap-psychoacoustics](https://zhenxianli.github.io/LISQM/projects/refmap-psychoacoustics.html) (the author's own code).
  - Unit tests check the standard's reference signal, which should give 1 tu_HMS, at 48 and 44.1 kHz.
  - RefMap's verification against ArtemiS v17.1, as for loudness.

## Before you compare numbers

Implementations of the same metric can give different numbers without either being wrong. Check these choices first.

- Input at other sample rates is resampled to 48 kHz.
- Overall roughness and fluctuation strength are 90th percentiles computed with NumPy (linear interpolation, Hyndman–Fan type 7). The MATLAB code it was translated from uses `prctile`, which interpolates differently, so single values can differ slightly from RefMap and SQAT.


## Notes

- The paper verifies the MATLAB implementations of the 3rd edition, from which this package was translated; it does not cover the Python package itself.
- Maintained by one person at the University of Salford (RefMap project). Requires Python 3.11 or newer.
- pySQAT calls this package for its ECMA-418-2 metrics.

## Before you rely on it

- Fluctuation strength is only on the main branch (not on PyPI yet) and its verification report is marked as a draft.
- Versions up to 0.1.13 are affected by an empty-array bug fixed in 0.1.14 ([#9](https://github.com/mlotinga/sottek-hearing-model/issues/9)).

## Sources

- https://github.com/mlotinga/sottek-hearing-model/blob/main/README.md
- https://github.com/mlotinga/sottek-hearing-model/blob/main/LICENSE
- https://github.com/mlotinga/sottek-hearing-model/blob/main/docs/validation/fluctuation_strength_verification.md
- https://pypi.org/project/sottek-hearing-model/
- https://github.com/mlotinga/sottek-hearing-model/issues/9
- https://github.com/mlotinga/sottek-hearing-model/tree/main/tests
- https://github.com/acoustics-code-salford/refmap-psychoacoustics/blob/main/validation/ECMA-418-2/README.md