hearing.threshold

Age-related hearing threshold (ISO 7029:2017) and audiometric reference zero (ISO 389-7:2005).

Implements the statistical distribution of the hearing threshold of an otologically normal population as a function of age and sex (ISO 7029:2017), and the reference threshold of hearing under free-field and diffuse-field listening (ISO 389-7:2005, Table 1), over the audiometric frequencies from 125 Hz to 8000 Hz.

ISO 7029 gives the median threshold deviation from the value at age 18 as dHmd = a * (age - 18) ** b (clause 4.2, Table 1) and the spread around the median as two half-Gaussian standard deviations su (worse than median) and sl (better than median), each a fifth-degree polynomial in age - 18 (clause 4.3, Tables 2-5). A population fractile is obtained by shifting the median by the standard-normal quantile times the appropriate spread (clause 4.4 / Annex A).

The noise-induced permanent threshold shift of ISO 1999 (which combines a noise component with this age component) is not part of this module.

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age_threshold

age_threshold(
    age: float,
    sex: Literal['male', 'female'] = 'male',
    fractile: float = 0.5,
    frequencies: ArrayLike | None = None,
) -> AgeThresholdResult

Age-related hearing threshold distribution (ISO 7029:2017).

Returns, per audiometric frequency, the median threshold deviation from the value at age 18 (clause 4.2), the upper/lower half-Gaussian spreads (clause 4.3) and the threshold at the requested population fractile (clause 4.4): median + z * spread where z is the standard-normal quantile of fractile and the spread is the upper one for z >= 0 (worse than the median) or the lower one otherwise.

Parameters

Name	Description
age	Listener age, in years (must be at least 18). The standard’s formulae are established up to 80 years for frequencies at or below 2000 Hz and up to 70 years above; ages beyond that extrapolate.
sex	"male" or "female".
fractile	Population fractile in the open interval (0, 1); 0.5 gives the median.
frequencies	Optional subset of the audiometric frequencies, in hertz; None uses all eleven (125 Hz - 8000 Hz).

Returns: An AgeThresholdResult with the distribution and .plot().

Raises

Exception	When
ValueError	for an age below 18, an unknown sex, a fractile outside (0, 1), or an unknown frequency.

AgeThresholdResult

AgeThresholdResult(
    age: float,
    sex: str,
    fractile: float,
    frequencies: np.ndarray,
    median: np.ndarray,
    spread_upper: np.ndarray,
    spread_lower: np.ndarray,
    threshold: np.ndarray,
)

Age-related hearing threshold distribution (ISO 7029:2017).

All arrays are in dB and aligned with AUDIOMETRIC_FREQUENCIES.

Attributes

Name	Description
age	Listener age, in years.
sex	"male" or "female".
fractile	Population fractile of threshold (0-1).
frequencies	Audiometric frequencies, in hertz.
median	Median threshold deviation from age 18 (clause 4.2).
spread_upper	Upper half-Gaussian standard deviation su.
spread_lower	Lower half-Gaussian standard deviation sl.
threshold	Threshold deviation at fractile (clause 4.4).

AgeThresholdResult.plot()

AgeThresholdResult.plot(
    ax: Axes | None = None,
    *,
    language: str = 'en',
    **kwargs: Any,
) -> Axes

Plot the median threshold with the fractile band over frequency.

Requires matplotlib (pip install phonometry[plot]); returns the Axes.

reference_threshold

reference_threshold(
    field: str = 'free-field',
    frequencies: ArrayLike | None = None,
) -> np.ndarray

Reference threshold of hearing (ISO 389-7:2005, Table 1).

The sound pressure level, in dB, that corresponds to the audiometric zero (0 dB HL) under the given listening condition, at the audiometric frequencies.

Parameters

Name	Description
field	"free-field" (frontal incidence) or "diffuse-field".
frequencies	Optional subset of the audiometric frequencies, in hertz; None uses all eleven (125 Hz - 8000 Hz).

Returns: The reference threshold, in dB, aligned with the frequencies.

Raises

Exception	When
ValueError	for an unknown field or frequency.