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phonometry
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psychoacoustics.quality.sharpness

Sharpness per DIN 45692:2009-08.

Sharpness rates the high-frequency emphasis of a sound in acum, computed as the g(z)-weighted first moment of the specific loudness pattern (DIN 45692 Equation 1) over the 24 Bark critical-band scale, normalized so the reference sound - critical-band-wide narrowband noise at 1 kHz (920 Hz to 1080 Hz) at 60 dB overall level - yields exactly 1.00 acum (clause 6). The informative Annex B variants of Aures and von Bismarck are provided as alternative methods with the literal factor 0.11 printed in Formulas (B.1)/(B.2); with it the reference sound lands near, not exactly at, 1.00 acum (~0.96 Aures / ~1.02 von Bismarck through this front-end).

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sharpness_din

Section titled “sharpness_din”
sharpness_din(
    x: Signal | list[float] | np.ndarray,
    fs: int | None = None,
    field: Literal['free', 'diffuse'] = 'free',
    method: Literal['din', 'aures', 'bismarck'] = 'din',
    calibration_factor: float | None = None,
) -> float

Sharpness of a signal per DIN 45692:2009 (stationary analysis).

The specific loudness comes from the ISO 532-1 Zwicker stationary method (the DIN 45631 basis named by DIN 45692); the sharpness is its g(z)-weighted first moment, normalized so the reference sound of clause 6 (critical-band-wide noise, 1 kHz, 60 dB) gives 1.00 acum. Verification tolerance per clause 6: 5 % or 0.05 acum against the Table A.2/A.3 target values. A small, systematic negative bias grows with centre frequency for narrowband stimuli (about -0.03 acum at 2.5 kHz to -0.15 acum at 8.5 kHz, from the specific-loudness upper-slope handling near the 24 Bark edge); it stays within the 5 % / 0.05 acum tolerance and is a known DIN 45692 implementation property.

Parameters

NameDescription
xInput signal (1D), in Pa after calibration_factor. Accepts a phonometry.io.Signal; the rate and the factor are resolved by loudness_zwicker, which this is a weighted moment of, so both arrive here on exactly the terms they have there.
fsSample rate in Hz. Required for a bare array; a Signal brings its own, and an explicit value that disagrees with it raises.
field'free' (default) or 'diffuse'.
method'din' (default), 'aures' or 'bismarck'.
calibration_factorDigital-units-to-Pa factor. An explicit value wins over the one a Signal carries.

Returns: Sharpness in acum.

sharpness_din_from_specific

Section titled “sharpness_din_from_specific”
sharpness_din_from_specific(
    specific: np.ndarray,
    method: Literal['din', 'aures', 'bismarck'] = 'din',
) -> float

Sharpness in acum from a specific-loudness pattern (DIN 45692 Eq. 1).

Parameters

NameDescription
specificSpecific loudness N’(z) at 0.1 Bark steps (240 values), e.g. ZwickerLoudness.specific.
method'din' (default, Eq. 1), or the informative Annex B variants 'aures' / 'bismarck'.

Returns: Sharpness in acum (0.0 for silence).

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