# Sharpness (DIN 45692, Aures, von Bismarck)

> 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/sharpness.html

**Quantity:** Sharpness · **Unit:** acum · **Also known as:** DIN 45692, acum, Zwicker sharpness, Aures sharpness, von Bismarck sharpness

Sharpness is the weighted first moment of specific loudness along the critical-band rate, with a weighting that emphasises high frequencies. DIN 45692:2009 standardises the weighting and a test procedure, using Zwicker specific loudness (ISO 532-1 / DIN 45631). Most implementations also offer the weightings of von Bismarck (1974) and Aures (1985).

The current edition is DIN 45692:2009. Open-source implementations of it: **[SQAT](https://zhenxianli.github.io/LISQM/projects/sqat.html)** (MATLAB; DIN 45692 weighting, plus von Bismarck and Aures options), **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)** (Python; weightings: DIN 45692, Aures, von Bismarck, Fastl), [refmap-psychoacoustics](https://zhenxianli.github.io/LISQM/projects/refmap-psychoacoustics.html) (MATLAB, Python; DIN 45692 weighting applied to ECMA-418-2 loudness), [MetaSona](https://zhenxianli.github.io/LISQM/projects/metasona.html) (C, Python; newly released, not yet seen to be widely used; from specific loudness), [Kirin Hypha](https://zhenxianli.github.io/LISQM/projects/kirin-hypha.html) (Rust; newly released, not yet seen to be widely used; from the time-varying specific loudness; shown in the plug-in), [Mosqito.NET](https://zhenxianli.github.io/LISQM/projects/mosqito-net.html) (C#; newly released, not yet seen to be widely used; weightings: DIN 45692, Aures, von Bismarck, Fastl), [phonometry](https://zhenxianli.github.io/LISQM/projects/phonometry.html) (Python; newly released, not yet seen to be widely used; also the informative Aures and von Bismarck variants), [PsychoacousticMetrics.jl](https://zhenxianli.github.io/LISQM/projects/psychoacousticmetrics-jl.html) (Julia; newly released, not yet seen to be widely used; weightings: DIN 45692 (default), Aures, von Bismarck, Fastl; from a ZwickerLoudness.jl result), [SoundPalette](https://zhenxianli.github.io/LISQM/projects/soundpalette.html) (C++; newly released, not yet seen to be widely used; from time-averaged specific loudness), [pySQAT](https://zhenxianli.github.io/LISQM/projects/pysqat.html) (Python; developing), and [PsychoacousticParametersMeasurer](https://zhenxianli.github.io/LISQM/projects/psychoacoustic-parameters-measurer.html) (Python; legacy, no commit since 2021-06). Implementations of earlier editions or related models: [AARAE](https://zhenxianli.github.io/LISQM/projects/aarae.html) (MATLAB; Fastl & Zwicker (2007); from the specific loudness of LoudnessCF) and [Swift & Gee codes](https://zhenxianli.github.io/LISQM/projects/rapid-loudness-sharpness.html) (MATLAB; legacy, no commit since 2020-01; Swift & Gee (2017); from Moore–Glasberg specific loudness, stationary and time-varying).

## Editions and who implements them

| Date | Edition | Status | What changed | Implemented by |
|---|---|---|---|---|
| 2017 | [Swift & Gee (2017)](https://doi.org/10.1121/1.5016193) | published | — | [Swift & Gee codes](https://zhenxianli.github.io/LISQM/projects/rapid-loudness-sharpness.html) |
| 2009-08 | [DIN 45692:2009](https://www.dinmedia.de/en/standard/din-45692/117635111) | current | Standardised weighting and test procedure; no revision announced. | **[SQAT](https://zhenxianli.github.io/LISQM/projects/sqat.html)**, **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)**, [refmap-psychoacoustics](https://zhenxianli.github.io/LISQM/projects/refmap-psychoacoustics.html), [MetaSona](https://zhenxianli.github.io/LISQM/projects/metasona.html), [Kirin Hypha](https://zhenxianli.github.io/LISQM/projects/kirin-hypha.html), [Mosqito.NET](https://zhenxianli.github.io/LISQM/projects/mosqito-net.html), [phonometry](https://zhenxianli.github.io/LISQM/projects/phonometry.html), [PsychoacousticMetrics.jl](https://zhenxianli.github.io/LISQM/projects/psychoacousticmetrics-jl.html), [SoundPalette](https://zhenxianli.github.io/LISQM/projects/soundpalette.html), [pySQAT](https://zhenxianli.github.io/LISQM/projects/pysqat.html), [PsychoacousticParametersMeasurer](https://zhenxianli.github.io/LISQM/projects/psychoacoustic-parameters-measurer.html) |
| 2007 | [Fastl & Zwicker (2007)](https://doi.org/10.1007/978-3-540-68888-4) | published | Zwicker & Fastl weighting as given in the textbook. | [AARAE](https://zhenxianli.github.io/LISQM/projects/aarae.html) |
| 1985 | [Aures (1985b)](https://zhenxianli.github.io/LISQM/standards.html#ref-aures-1985-euphony) | published | Weighting that depends on total loudness. | — |
| 1974 | [von Bismarck (1974)](https://www.ingentaconnect.com/contentone/dav/aaua/1974/00000030/00000003/art00006) | published | Original sharpness weighting. | — |

## Project map

The lines of the project map for sharpness 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 **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)**: [Kirin Hypha](https://zhenxianli.github.io/LISQM/projects/kirin-hypha.html) (DIN 45692:2009); [Mosqito.NET](https://zhenxianli.github.io/LISQM/projects/mosqito-net.html) (DIN 45692:2009)
- From **[SQAT](https://zhenxianli.github.io/LISQM/projects/sqat.html)**: [pySQAT](https://zhenxianli.github.io/LISQM/projects/pysqat.html) (DIN 45692:2009)

### Used at run time

- [rota-order](https://zhenxianli.github.io/LISQM/projects/rota-order.html) calls **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)** (DIN 45692:2009)
- [rota-order](https://zhenxianli.github.io/LISQM/projects/rota-order.html) calls **[SQAT](https://zhenxianli.github.io/LISQM/projects/sqat.html)** (DIN 45692:2009)
- [PsychoBox](https://zhenxianli.github.io/LISQM/projects/psychobox.html) calls **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)** (DIN 45692:2009)
- [Soundscapy](https://zhenxianli.github.io/LISQM/projects/soundscapy.html) calls **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)** (DIN 45692:2009)

### Results checked against another project

- [PsychoacousticMetrics.jl](https://zhenxianli.github.io/LISQM/projects/psychoacousticmetrics-jl.html) against **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)** (DIN 45692:2009)
- [SoundPalette](https://zhenxianli.github.io/LISQM/projects/soundpalette.html) against **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)** (DIN 45692:2009)

### Same contributor

- **[SQAT](https://zhenxianli.github.io/LISQM/projects/sqat.html)** and [refmap-psychoacoustics](https://zhenxianli.github.io/LISQM/projects/refmap-psychoacoustics.html) (Mike Lotinga)

On the map without a line, as no relation to another project listed for sharpness is recorded for them: [AARAE](https://zhenxianli.github.io/LISQM/projects/aarae.html), [MetaSona](https://zhenxianli.github.io/LISQM/projects/metasona.html), [phonometry](https://zhenxianli.github.io/LISQM/projects/phonometry.html), [PsychoacousticParametersMeasurer](https://zhenxianli.github.io/LISQM/projects/psychoacoustic-parameters-measurer.html), and [Swift & Gee codes](https://zhenxianli.github.io/LISQM/projects/rapid-loudness-sharpness.html).

## Implementations

| Project | Language | Edition | Functions | Validation (as stated) | Notes |
|---|---|---|---|---|---|
| **[SQAT](https://zhenxianli.github.io/LISQM/projects/sqat.html)** | MATLAB | [DIN 45692:2009](https://www.dinmedia.de/en/standard/din-45692/117635111) (DIN 45692 weighting, plus von Bismarck and Aures options; since v1.0) | `Sharpness_DIN45692`, `Sharpness_DIN45692_from_loudness`, `Sharpness_DIN45692_from_wavfile` | standard or paper data | — |
| **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)** | Python | [DIN 45692:2009](https://www.dinmedia.de/en/standard/din-45692/117635111) (weightings: DIN 45692, Aures, von Bismarck, Fastl; since 1.0.2) | `sharpness_din_st`, `sharpness_din_tv`, `sharpness_din_perseg`, `sharpness_din_from_loudness`, `sharpness_din_freq` | standard or paper data (outcome not stated) | — |
| [refmap-psychoacoustics](https://zhenxianli.github.io/LISQM/projects/refmap-psychoacoustics.html) | MATLAB, Python | [DIN 45692:2009](https://www.dinmedia.de/en/standard/din-45692/117635111) (DIN 45692 weighting applied to ECMA-418-2 loudness) | `acousticSharpnessSHM`, `acousticSharpFromSHMLoud` | not stated | The DIN 45692 weighting is the option `widmann`; Aures (the default) and von Bismarck weightings are also offered. DIN 45692 itself is defined on Zwicker specific loudness. A further variant works from a Zwicker-based quasi-loudness (`acousticSharpFromQuasiLoud`). An inaccuracy in the Aures weighting was fixed on 2026-09-18. |
| [AARAE](https://zhenxianli.github.io/LISQM/projects/aarae.html) | MATLAB | [Fastl & Zwicker (2007)](https://doi.org/10.1007/978-3-540-68888-4) (from the specific loudness of LoudnessCF) | `sharpness_Fastl` | not stated | The header describes a weighting fitted to data in Zwicker & Fastl's *Psychoacoustics: Facts and Models* (edition not stated), names the method "Fastl (1991)" and credits Claire Churchill (2004). |
| [MetaSona](https://zhenxianli.github.io/LISQM/projects/metasona.html) | C, Python | [DIN 45692:2009](https://www.dinmedia.de/en/standard/din-45692/117635111) (from specific loudness; since 0.1.0) | `sharpness_din45692` | not stated | Newly released project, not yet seen to be widely used. |
| [Kirin Hypha](https://zhenxianli.github.io/LISQM/projects/kirin-hypha.html) | Rust | [DIN 45692:2009](https://www.dinmedia.de/en/standard/din-45692/117635111) (from the time-varying specific loudness; shown in the plug-in; since 1.0.0) | `kirin_measure::phase_d::sharpness` | compared with MoSQITo (its source) | Newly released project, not yet seen to be widely used. |
| [Mosqito.NET](https://zhenxianli.github.io/LISQM/projects/mosqito-net.html) | C# | [DIN 45692:2009](https://www.dinmedia.de/en/standard/din-45692/117635111) (weightings: DIN 45692, Aures, von Bismarck, Fastl) | `Sq.SharpnessDinSt`, `Sq.SharpnessDinTv`, `Sq.SharpnessDinPerSeg`, `Sq.SharpnessDinFreq` | compared with MoSQITo (its source) | Newly released project, not yet seen to be widely used. |
| [phonometry](https://zhenxianli.github.io/LISQM/projects/phonometry.html) | Python | [DIN 45692:2009](https://www.dinmedia.de/en/standard/din-45692/117635111) (also the informative Aures and von Bismarck variants; since 3.1.0) | `sharpness_din`, `sharpness_din_from_specific` | standard or paper data | Newly released project, not yet seen to be widely used. |
| [PsychoacousticMetrics.jl](https://zhenxianli.github.io/LISQM/projects/psychoacousticmetrics-jl.html) | Julia | [DIN 45692:2009](https://www.dinmedia.de/en/standard/din-45692/117635111) (weightings: DIN 45692 (default), Aures, von Bismarck, Fastl; from a ZwickerLoudness.jl result; since 0.2.0) | `sharpness` | standard or paper data; also compared with MoSQITo | Newly released project, not yet seen to be widely used. Uses ZwickerLoudness.jl. |
| [SoundPalette](https://zhenxianli.github.io/LISQM/projects/soundpalette.html) | C++ | [DIN 45692:2009](https://www.dinmedia.de/en/standard/din-45692/117635111) (from time-averaged specific loudness; since v0.5.0) | `sp::compute_psycho` | compared with MoSQITo | Newly released project, not yet seen to be widely used. A source-available licence, not an open-source one: some uses are not allowed. |
| [pySQAT](https://zhenxianli.github.io/LISQM/projects/pysqat.html) | Python | [DIN 45692:2009](https://www.dinmedia.de/en/standard/din-45692/117635111) | `Sharpness_DIN45692`, `Sharpness_DIN45692_from_loudness` | 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. |
| [Swift & Gee codes](https://zhenxianli.github.io/LISQM/projects/rapid-loudness-sharpness.html) | MATLAB | [Swift & Gee (2017)](https://doi.org/10.1121/1.5016193) (from Moore–Glasberg specific loudness, stationary and time-varying) | `stationaryLoudness`, `Glasberg_loudness` | not stated | Legacy project, no longer maintained. |
| [PsychoacousticParametersMeasurer](https://zhenxianli.github.io/LISQM/projects/psychoacoustic-parameters-measurer.html) | Python | [DIN 45692:2009](https://www.dinmedia.de/en/standard/din-45692/117635111) | `calc_sharpness` | not stated | Legacy project, no longer maintained. No licence file: by default, copying, changing or sharing the code needs the author's permission. The file header says "Sharpness DIN 45692"; the function also returns the von Bismarck and Aures variants. |

Also available through tools that call one of these implementations: [rota-order](https://zhenxianli.github.io/LISQM/projects/rota-order.html) (via MoSQITo, DIN 45692:2009), [PsychoBox](https://zhenxianli.github.io/LISQM/projects/psychobox.html) (via MoSQITo, DIN 45692:2009), and [Soundscapy](https://zhenxianli.github.io/LISQM/projects/soundscapy.html) (via MoSQITo, DIN 45692:2009).

**See also:** [Zwicker loudness (ISO 532-1, DIN 45631)](https://zhenxianli.github.io/LISQM/metrics/loudness-zwicker.html)

## 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)**, DIN 45692:2009: standard or paper data
  - Checked with the narrowband and broadband test signals of DIN 45692.
- **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)**, DIN 45692:2009: standard or paper data (outcome not stated)
  - Validation scripts use the DIN 45692 test signals; the documentation marks it as validated.
- [Kirin Hypha](https://zhenxianli.github.io/LISQM/projects/kirin-hypha.html), DIN 45692:2009: compared with **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)** (its source)
  - Ported or adapted from **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)**. It was compared with the code it was ported from, which checks the port only.
  - Tests assert agreement with MoSQITo within 0.05 acum.
- [Mosqito.NET](https://zhenxianli.github.io/LISQM/projects/mosqito-net.html), DIN 45692:2009: compared with **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)** (its source)
  - Ported or adapted from **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)**. It was compared with the code it was ported from, which checks the port only.
  - Every public function is compared with the output of Python MoSQITo for seven WAV files (three of them ISO 532-1 test signals), within 1 % (0.5 dB for levels); MoSQITo's unit tests are ported too.
- [phonometry](https://zhenxianli.github.io/LISQM/projects/phonometry.html), DIN 45692:2009: standard or paper data
  - Checked with the DIN 45692 reference signal and Tables A.2 and A.3.
- [PsychoacousticMetrics.jl](https://zhenxianli.github.io/LISQM/projects/psychoacousticmetrics-jl.html), DIN 45692:2009: standard or paper data; also compared with **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)**
  - Tested against all 41 reference signals of DIN 45692:2009 chapter 6 (21 narrowband, 20 broadband) within the standard's tolerance of ±max(5 %, 0.05 acum).
  - Cross-checked against MoSQITo for all four weightings.
  - Total loudness N is computed as the Riemann sum over the 240-bin specific loudness (`0.1 * sum`), not taken from `ZwickerResult.loudness` (see the `sharpness` docstring).
- [SoundPalette](https://zhenxianli.github.io/LISQM/projects/soundpalette.html), DIN 45692:2009: compared with **[MoSQITo](https://zhenxianli.github.io/LISQM/projects/mosqito.html)**
  - Compared with MoSQITo 1.2.1 (tolerance ±5 %).
- [rota-order](https://zhenxianli.github.io/LISQM/projects/rota-order.html) (via MoSQITo), DIN 45692:2009 (through MoSQITo's sharpness_din_from_loudness): own tests only
  - Tests, which run only where MoSQITo is installed (the project's continuous integration does not install it), check that the wrapper returns what a direct call of MoSQITo gives, also when the sharpness is computed from an earlier loudness result.
- [rota-order](https://zhenxianli.github.io/LISQM/projects/rota-order.html) (via SQAT), DIN 45692:2009 (through SQAT v2.0's Sharpness_DIN45692_from_loudness in MATLAB): own tests only
  - Tests with a stub engine check the call passed to SQAT and the conversion of its output; the comparison with a direct SQAT call runs only where MATLAB and SQAT v2.0 are installed.
- [pySQAT](https://zhenxianli.github.io/LISQM/projects/pysqat.html), DIN 45692:2009: 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 refmap-psychoacoustics, AARAE, MetaSona, Swift & Gee codes, PsychoacousticParametersMeasurer, PsychoBox, and Soundscapy.

## Before you compare numbers

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

- **Weighting.** The DIN 45692, Aures and von Bismarck weightings give different values for the same sound, and Aures' weighting depends on loudness. Many tools offer several; check which one is used (RefMap's default is Aures).
- **Loudness input.** Sharpness is computed from Zwicker specific loudness, so the loudness choices (sound field, calibration, sample rate) carry over. Sharpness from another loudness model, such as ECMA-418-2 (RefMap) or Moore–Glasberg (Swift & Gee), is a different quantity.

What the projects state:

- **[SQAT](https://zhenxianli.github.io/LISQM/projects/sqat.html)**: Statistics such as N5 take the nearest rank of the sorted time series, without interpolation (`get_exceeded_value`), and leave out the first `time_skip` seconds of the signal.
- [MetaSona](https://zhenxianli.github.io/LISQM/projects/metasona.html): Expects calibrated sound pressure in pascals. The C functions require 48 kHz input; the Python interface resamples other rates to 48 kHz (SciPy `resample_poly`). `time_skip_s` (default 0 s) leaves out the start of the signal from the reported frames; the computation still runs over the whole signal. Time-varying results include every complete frame, labelled at frame centres, which differs from SQAT's handling of the last frame and of time stamps.
- [rota-order](https://zhenxianli.github.io/LISQM/projects/rota-order.html): The method `vs_rpm` of a wrapper's result bins it along rpm after leaving out the start of the signal: by default it takes in each speed bin the 95th percentile of the loudness (N5), the median of the sharpness and the 90th percentile of the roughness, after 0.6 s for loudness and sharpness and 1.5 s for roughness. Keyword arguments override these choices. Input in any unit is turned into sound pressure in Pa by an explicit calibration factor and resampled to 48 kHz.
- [Swift & Gee codes](https://zhenxianli.github.io/LISQM/projects/rapid-loudness-sharpness.html): The code works at 32 kHz; other rates are resampled with the Signal Processing Toolbox's `resample`.

## References

1. von Bismarck, G. (1974). Sharpness as an attribute of the timbre of steady sounds. *Acustica*, 30(3), 159–172. https://www.ingentaconnect.com/contentone/dav/aaua/1974/00000030/00000003/art00006
2. Aures, W. (1985). Berechnungsverfahren für den sensorischen Wohlklang beliebiger Schallsignale [A model for calculating the sensory euphony of various sounds]. *Acustica*, 59, 130–141.
3. Fastl, H., & Zwicker, E. (2007). *Psychoacoustics: Facts and models* (3rd ed.). Springer. https://doi.org/10.1007/978-3-540-68888-4
4. DIN 45692:2009. Messtechnische Simulation der Hörempfindung Schärfe (Measurement technique for the simulation of the auditory sensation of sharpness). https://www.dinmedia.de/en/standard/din-45692/117635111
5. Swift, S. H., & Gee, K. L. (2017). Extending sharpness calculation for an alternative loudness metric input. *The Journal of the Acoustical Society of America*, 142(6), EL549. https://doi.org/10.1121/1.5016193