hearing.threshold

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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 $d H_{md} = a (age - 18)^{b}$ (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.

AUDIOMETRIC_FREQUENCIES

Constant (numpy.ndarray, shape (11,)).

EARPHONE_COUPLERS

Constant (mapping).

EARPHONE_COUPLERS = {'DT 48': 'IEC 60303 acoustic coupler', 'TDH 39': 'IEC 60303 acoustic coupler', 'other supra-aural': 'IEC 60318 artificial ear'}

earphone_reference_level

earphone_reference_level(
    earphone: str = 'TDH 39',
    frequencies: ArrayLike | None = None,
) -> np.ndarray

Reference equivalent threshold sound pressure level (ISO 389-1:1998).

The sound pressure level, in dB re 20 uPa, that an audiometer has to produce in the coupler for a hearing level of 0 dB HL. It is what audiometric zero means for a supra-aural earphone, and it depends on the earphone model and on the coupler it is calibrated on, which is why the standard prints two tables rather than one.

Parameters

Name	Description
`earphone`	`"DT 48"` or `"TDH 39"` (Table 1, on the IEC 60303 coupler), or `"other supra-aural"` (Table 2, on the IEC 60318 artificial ear, for an earphone meeting the requirements of 4.3).
`frequencies`	Optional subset of `RETSPL_FREQUENCIES_HZ`, in hertz; `None` uses all twenty-three.

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

Raises

Exception	When
ValueError	For an unknown earphone or frequency.

EARPHONES

Constant (tuple).

EARPHONES = ('DT 48', 'TDH 39', 'other supra-aural')

FIELDS

Constant (tuple).

FIELDS = ('free-field', 'diffuse-field')

hearing_level_to_coupler_spl

hearing_level_to_coupler_spl(
    hearing_level: ArrayLike,
    earphone: str = 'TDH 39',
    frequencies: ArrayLike | None = None,
) -> np.ndarray

An audiogram in dB HL as the level the coupler has to see, in dB SPL.

Hearing level is defined against the audiometric zero, so the two differ by the reference level of the earphone and nothing else: an audiogram of 0 dB HL is the reference level itself, and every decibel of hearing loss is a decibel more in the coupler.

Parameters

Name	Description
`hearing_level`	The audiogram, in dB HL, one value per frequency.
`earphone`	As in `earphone_reference_level`.
`frequencies`	The frequencies the audiogram was taken at; `None` uses all twenty-three of `RETSPL_FREQUENCIES_HZ`.

Returns: The equivalent sound pressure level in the coupler, in dB.

Raises

Exception	When
ValueError	If the audiogram does not match the frequencies, or for an unknown earphone or frequency.

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.

RETSPL_FREQUENCIES_HZ

Constant (numpy.ndarray, shape (23,)).

SEXES

Constant (tuple).

SEXES = ('male', 'female')

Creado y mantenido por José Manuel Requena Plens ORCID Todos los proyectos