# Perceived noise level, PNLT and EPNL (ICAO Annex 16, 14 CFR Part 36)

> 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/metrics/epnl.html

**Quantity:** Related quantities · **Unit:** PNdB, EPNdB · **Also known as:** EPNL, EPNdB, PNL, PNLT, perceived noisiness, noy, aircraft noise certification

Effective perceived noise level for aircraft noise certification: perceived noisiness in noy, the tone-corrected perceived noise level (PNLT) and a duration correction. Defined in ICAO Annex 16, Volume I, and in the US regulation 14 CFR Part 36.

The current edition is ICAO Annex 16, Vol. I and 14 CFR Part 36. Open-source implementations of it: **[SQAT](https://zhenxianli.github.io/LISQM/projects/sqat.html)** (MATLAB; 14 CFR Part 36), [phonometry](https://zhenxianli.github.io/LISQM/projects/phonometry.html) (Python; newly released, not yet seen to be widely used; ICAO Annex 16, Vol. I; PNL, PNLT and EPNL, in the phonometry.aircraft namespace), [pySQAT](https://zhenxianli.github.io/LISQM/projects/pysqat.html) (Python; developing; 14 CFR Part 36), and [SUAVE](https://zhenxianli.github.io/LISQM/projects/suave.html) (Python; legacy, no commit since 2022-12; ICAO Annex 16, Vol. I; PNL, PNLT and EPNL; the code cites no edition).

## Editions and who implements them

| Date | Edition | Status | What changed | Implemented by |
|---|---|---|---|---|
| 2017-07 | [ICAO Annex 16, Vol. I](https://store.icao.int/en/annex-16-environmental-protection-volume-i-aircraft-noise) | current; Amendment 15 was adopted on 2026-03-27 and applies from 2027-01-01 (new noise limits and supersonic aeroplanes); whether it changes the EPNL procedure itself has not been confirmed. | International standard for aircraft noise certification. | [phonometry](https://zhenxianli.github.io/LISQM/projects/phonometry.html), [SUAVE](https://zhenxianli.github.io/LISQM/projects/suave.html), [Zhen-Ni/epnl](https://zhenxianli.github.io/LISQM/projects/zhen-ni-epnl.html) |
| 2002-07 | [14 CFR Part 36](https://www.ecfr.gov/current/title-14/chapter-I/subchapter-C/part-36) | current | US regulation (Appendices A and B). | **[SQAT](https://zhenxianli.github.io/LISQM/projects/sqat.html)**, [pySQAT](https://zhenxianli.github.io/LISQM/projects/pysqat.html) |

## Project map

The lines of the project map for perceived noise level and EPNL only, between the projects listed for it (the whole map: https://zhenxianli.github.io/LISQM/projects/map.md). Agreement between a project and the code it was ported or adapted from only checks the port.

### Ported or adapted from another project

- From **[SQAT](https://zhenxianli.github.io/LISQM/projects/sqat.html)**: [pySQAT](https://zhenxianli.github.io/LISQM/projects/pysqat.html) (14 CFR Part 36)

On the map without a line, as no relation to another project listed for perceived noise level and EPNL is recorded for them: [phonometry](https://zhenxianli.github.io/LISQM/projects/phonometry.html), [SUAVE](https://zhenxianli.github.io/LISQM/projects/suave.html), and [Zhen-Ni/epnl](https://zhenxianli.github.io/LISQM/projects/zhen-ni-epnl.html).

## Implementations

| Project | Language | Edition | Functions | Validation (as stated) | Notes |
|---|---|---|---|---|---|
| **[SQAT](https://zhenxianli.github.io/LISQM/projects/sqat.html)** | MATLAB | [14 CFR Part 36](https://www.ecfr.gov/current/title-14/chapter-I/subchapter-C/part-36) (since v1.1) | `EPNL_FAR_Part36`, `get_PNL`, `get_PNLT`, `get_Duration_Correction` | compared with published EPNL values (Rizzi et al., 2020) | Follows Amendment 36-26 (2005). |
| [phonometry](https://zhenxianli.github.io/LISQM/projects/phonometry.html) | Python | [ICAO Annex 16, Vol. I](https://store.icao.int/en/annex-16-environmental-protection-volume-i-aircraft-noise) (PNL, PNLT and EPNL, in the phonometry.aircraft namespace) | — | standard or paper data | Newly released project, not yet seen to be widely used. |
| [pySQAT](https://zhenxianli.github.io/LISQM/projects/pysqat.html) | Python | [14 CFR Part 36](https://www.ecfr.gov/current/title-14/chapter-I/subchapter-C/part-36) | `EPNL_FAR_Part36` | compared with SQAT (its source) | Developing project: no publication or documented use by others. No licence file: by default, copying, changing or sharing the code needs the author's permission. |
| [SUAVE](https://zhenxianli.github.io/LISQM/projects/suave.html) | Python | [ICAO Annex 16, Vol. I](https://store.icao.int/en/annex-16-environmental-protection-volume-i-aircraft-noise) (PNL, PNLT and EPNL; the code cites no edition) | `pnl_noise`, `noise_tone_correction`, `epnl_noise` | not stated | Legacy project, no longer maintained. EPNL is computed from a PNLT time history. The noise tools cite neither ICAO Annex 16 nor 14 CFR Part 36, nor an edition; their docstrings give "Source: None". |
| [Zhen-Ni/epnl](https://zhenxianli.github.io/LISQM/projects/zhen-ni-epnl.html) | Rust | [ICAO Annex 16, Vol. I](https://store.icao.int/en/annex-16-environmental-protection-volume-i-aircraft-noise) (PNL and PNLT only; no duration correction to EPNL) | `SPL`, `Noy`, `PNL`, `PNLT` | not stated | Legacy project, no longer maintained. No licence file: by default, copying, changing or sharing the code needs the author's permission. Partial: computes only part of the metric. Code comments cite "Annex 16 - Volume I, APP 2-16 / 2-17" and number the 24 bands "consistent with ICAO ANNEX 16". The quantities are Rust types converted into each other with `From`. |

## How they were validated

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

- **[SQAT](https://zhenxianli.github.io/LISQM/projects/sqat.html)**, 14 CFR Part 36: compared with published EPNL values (Rizzi et al., 2020)
  - The README says that no reference implementation or test signals exist, so the verification is partial.
  - Perceived noisiness is checked at its definition (a third-octave band of noise at 1 kHz and 40 dB SPL gives 1 noy), and the tone correction factor against Table 3.7 of ICAO Doc 9501.
  - EPNL is cross-checked with Table 4 of Rizzi et al. (2020), AIAA 2020-2582, for 15 flyover sounds (five cases auralised by three tools): the largest difference is about 0.6 EPNdB.
- [phonometry](https://zhenxianli.github.io/LISQM/projects/phonometry.html), ICAO Annex 16, Vol. I: standard or paper data
  - Tested with the EPNL example of ICAO Doc 9501 (Environmental Technical Manual).
- [pySQAT](https://zhenxianli.github.io/LISQM/projects/pysqat.html), 14 CFR Part 36: compared with **[SQAT](https://zhenxianli.github.io/LISQM/projects/sqat.html)** (its source)
  - Ported or adapted from **[SQAT](https://zhenxianli.github.io/LISQM/projects/sqat.html)**. It was compared with the code it was ported from, which checks the port only.
  - Compared with SQAT v1.3, run in MATLAB, by `validation/FINAL_VAL.py`; the generated reports are not committed.

Not stated by SUAVE and Zhen-Ni/epnl.

## References

1. 14 CFR Part 36. Noise standards: aircraft type and airworthiness certification (Appendix A: EPNL). https://www.ecfr.gov/current/title-14/chapter-I/subchapter-C/part-36
2. ICAO Annex 16, Vol. I. Annex 16 to the Convention on International Civil Aviation — Environmental Protection — Volume I: Aircraft Noise. https://store.icao.int/en/annex-16-environmental-protection-volume-i-aircraft-noise