metrology.reciprocity_free_field

La referencia de la API se publica en inglés en los dos idiomas: se genera a partir de los docstrings del código, que son su texto original.

Free-field calibration of laboratory standard microphones by reciprocity (IEC 61094-3:2016 with its corrigendum IEC 61094-3:2016/COR1:2016).

Two microphones face each other in a free field with their principal axes in line. A current $i_{1}$ through the transmitter makes it, seen from far enough, a simple source of strength $M_{f, 1} i_{1}$ placed at its acoustic centre, and the spherical wave it radiates reaches the acoustic centre of the receiver at the distance $d_{12}$ as (Formula (6))

p_{0} = j \frac{ρ f}{2 d _{12}} M_{f, 1} i_{1} e^{- j k d_{12}} e^{- α d_{m 12}}

attenuated by the air over $d_{m 12}$ , the distance the wave actually travels between the diaphragms. The receiver turns it into $U_{2} = M_{f, 2} p_{0}$ , so the product of the two free-field sensitivities is (Formula (7))

M_{f, 1} M_{f, 2} = - j \frac{2 d _{12}}{ρ f} \frac{U _{2}}{i _{1}} e^{j k d_{12}} e^{α d_{m 12}}

and three pairs give each sensitivity (Formula (8)), or one pair and the ratio of the two sensitivities measured against an auxiliary source give both (Formula (9), the complex sensitivity since COR1).

The factor $- j$ . Formula (7) carries it and Formulas (8) and (9) do not, although (8) is the quotient of three products of the form (7) and (9) the product of one of them with $r_{12}$ . The modulus does not see the difference, and before the corrigendum (9) gave the modulus only; the phase does, by 45°. The library takes the factor through from Formula (7) and Formula (D.1), which agree with each other; the defect is recorded in docs/ERRATA.md.

The attenuation of sound in air (7.4 and Annex B). $α$ is the real part of the propagation coefficient, computed by the five steps of B.2 (reciprocity_air_attenuation): ISO 9613-1 adjusted to the quantities of IEC 61094-2, with the speed of sound at the conditions of the calibration in the vibrational terms. Step 1 prints the last coefficient of the saturation vapour pressure as $6, 33431845 \cdot 1 0^{3}$ , where IEC 61094-2 Table F.2, which the step refers to, prints $6, 3431645 \times 1 0^{3}$ ; the library uses the latter (an erratum). Table B.1 tabulates the attenuation by ISO 9613-1 itself, as its text says, and air_attenuation reproduces every one of its 162 entries.

The wave number $k = ω / c$ takes the speed of sound of IEC 61094-2 Annex F (air), by default with the dispersion of its NOTE to F.3: $c = c_{0} [1 + \sum_{n} c α_{v n} / (2 π f_{v n})]$ , a few parts in $1 0^{5}$ that reach a few tenths of a degree of phase at 20 kHz over 0,2 m. Annex B.1 points to it (“including dispersion effects”).

Acoustic centres (6.5 and Annex A). The distance $d_{12}$ is between the acoustic centres, each given as its position on the principal axis relative to the diaphragm, positive in front of it, a value or one per frequency; Annex A shows them only as a figure. acoustic_centre finds one from the inverse-distance law, as 6.5 describes.

The arrangement (6.4, 7.3). check_free_field_arrangement holds the distance between the microphones to the ten nominal diameters 7.3 recommends and their supporting cylinders to the twenty 6.4 recommends, and the conditions to the domain in which Annex B states the accuracy of the attenuation: its verdict is whether the arrangement is the recommended one.

Auto-generated from the source docstrings by scripts/generate_api_docs.py (make api-docs). Do not edit by hand.

acoustic_centre

acoustic_centre(
    distances_m: ArrayLike,
    sound_pressures_pa: ArrayLike,
    *,
    attenuation_np_per_m: float = 0.0,
) -> AcousticCentre

The position of the acoustic centre of a microphone used as a source (IEC 61094-3:2016 6.5).

“In a limited region of the far field, the sound pressure, corrected for the effect of sound attenuation, will follow the 1/r-law, r being referred now to the acoustic centre of the microphone. Thus, when plotting the inverse value of the measured sound pressure as a function of the distance from an arbitrarily chosen reference point of the microphone (most conveniently the centre of the diaphragm), a straight line can be fitted (e.g. by the methods of least squares) through the plotted values. The intersection of this straight line and the abscissa axis determines the position of the acoustic centre relative to the reference point.”

The pressures may be in any unit proportional to the sound pressure, such as the receiver’s output voltage at one frequency; each is multiplied by $e^{α r}$ before it is inverted.

Parameters

Name	Description
`distances_m`	The distances from the reference point, in m, at least three, positive.
`sound_pressures_pa`	The modulus of the sound pressure at each, in Pa or any proportional unit, positive.
`attenuation_np_per_m`	$α$ at the frequency, in Np/m (Default: 0), from `reciprocity_air_attenuation`.

Returns: The AcousticCentre.

Raises

Exception	When
ValueError	for fewer than three distances, columns of different lengths, values that are not positive and finite, or distances that are all the same.

AcousticCentre

AcousticCentre(
    distances_m: NDArray[np.float64],
    inverse_readings: NDArray[np.float64],
    slope: float,
    intercept: float,
)

The position of the acoustic centre of a microphone from the inverse-distance law (IEC 61094-3:2016 6.5).

Attributes

Name	Description
`distances_m`	The distances from the reference point of the microphone to the observation points, in m.
`inverse_readings`	$1/∣ p ∣$ , corrected for the attenuation of sound, at each distance, in the reciprocal of the unit the pressures were given in.
`slope`	The slope of the straight line fitted by least squares.
`intercept`	Its intercept at zero distance.

AcousticCentre.plot()

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

Plot the inverse pressures, the fitted line and where it crosses the axis.

Parameters

Name	Description
`ax`	Existing axes to draw on, or `None` to create a figure.
`language`	Label language, `"en"` (default) or `"es"`.
`kwargs`	Forwarded to the fitted line.

Returns: The axes. Requires matplotlib (pip install phonometry[plot]).

AcousticCentre.position_m

property

The acoustic centre relative to the reference point, in m: where the fitted line crosses the axis, $- b / a$ ; positive towards the observation points, which for a reference point on the diaphragm is in front of it (Annex A).

check_free_field_arrangement

check_free_field_arrangement(
    frequencies_hz: ArrayLike,
    *,
    diaphragm_distances_m: Sequence[float],
    microphone_diameter_m: float,
    temperature_c: float,
    static_pressure_pa: float,
    relative_humidity_percent: float,
    support_length_m: float | None = None,
) -> FreeFieldArrangementCheck

Is this the free-field arrangement IEC 61094-3:2016 recommends?

7.3 recommends a distance between the microphones greater than ten times their nominal diameter, “to ensure an approximately plane wave in a suitable region around the receiving microphone”; 6.4 recommends attaching each microphone to a cylinder of its diameter at least twenty diameters long; and B.2 states the accuracy of the attenuation within a domain of temperature, static pressure, water vapour and frequency-to-pressure ratio. Annex A allows the published acoustic centres between 150 mm and 500 mm, which is reported without entering the verdict.

Parameters

Name	Description
`frequencies_hz`	The frequencies of the calibration, in Hz.
`diaphragm_distances_m`	The distance of each pair, in m.
`microphone_diameter_m`	The nominal diameter of the microphones, in m (23,77 mm for LS1, 13,2 mm for LS2a: dimension A of Table C.1 of IEC 61094-2).
`temperature_c`	The temperature, in °C.
`static_pressure_pa`	The static pressure, in Pa.
`relative_humidity_percent`	The relative humidity, in %.
`support_length_m`	The length of the supporting cylinder, in m, or `None` if not known.

Returns: The FreeFieldArrangementCheck.

Raises

Exception	When
ValueError	for no distance, or a distance, diameter or length that is not positive.

free_field_parameter_uncertainty

free_field_parameter_uncertainty(
    frequencies_hz: ArrayLike,
    uncertainties: FreeFieldInputUncertainties,
    *,
    diaphragm_distances_m: Sequence[float],
    temperature_c: float,
    static_pressure_pa: float,
    relative_humidity_percent: float,
    acoustic_centres_m: Sequence[ArrayLike] = (0.0, 0.0, 0.0),
    microphone: int = 1,
    dispersion: bool = True,
) -> FreeFieldParameterUncertainty

The uncertainty components of the free-field acoustic transfer impedance, one parameter at a time (IEC 61094-3:2016 7.8).

As in IEC 61094-2 7.5, each parameter with a non-zero standard uncertainty is moved by it, the three products of Formula (7) recomputed with the electrical transfer impedances held, and the change of the level of microphone by Formula (8) is its component. The distance of each pair and the acoustic centre of each microphone are moved one at a time, as independent quantities, and their changes combined in quadrature into the single rows “Distance” and “Acoustic centres” of Table 1. The attenuation is moved by a fraction of itself, FreeFieldInputUncertainties.u_air_attenuation_ratio.

Parameters

Name	Description
`frequencies_hz`	The frequencies, in Hz, increasing.
`uncertainties`	The standard uncertainty of each input quantity, a `FreeFieldInputUncertainties`.
`diaphragm_distances_m`	$d_{m 12}$ , $d_{m 23}$ , $d_{m 31}$ , in m.
`temperature_c`	The temperature, in °C.
`static_pressure_pa`	The static pressure, in Pa.
`relative_humidity_percent`	The relative humidity, in %.
`acoustic_centres_m`	The three acoustic centres, in m.
`microphone`	The microphone whose level is analysed, 1, 2 or 3.
`dispersion`	Whether $k$ includes dispersion (Default: `True`).

Returns: The FreeFieldParameterUncertainty.

Raises

Exception	When
ValueError	for other than three distances or centres, a microphone that is not 1, 2 or 3, or acoustic-centre uncertainties that are not one value or one per frequency.

free_field_reciprocity

free_field_reciprocity(
    frequencies_hz: ArrayLike,
    electrical_transfer_impedances_ohm: Sequence[ArrayLike],
    *,
    diaphragm_distances_m: Sequence[float],
    temperature_c: float,
    static_pressure_pa: float,
    relative_humidity_percent: float,
    acoustic_centres_m: Sequence[ArrayLike] = (0.0, 0.0, 0.0),
    dispersion: bool = True,
    corrections_db: Mapping[str, ArrayLike] | None = None,
    expanded_uncertainty_db: ArrayLike | None = None,
) -> ReciprocityCalibration

The free-field sensitivities of three microphones calibrated in pairs (IEC 61094-3:2016 5.7.1, Formula (8)).

Each pair gives the product of Formula (7), with $d_{ij}$ the distance between the acoustic centres and $d_{m ij}$ that between the diaphragms; facing each other, $d_{ij} = d_{m ij} - x_{i} - x_{j}$ with $x$ the position of each acoustic centre in front of its diaphragm. The three are solved as Formula (8) asks:

M_{f, 1} = (- j \frac{2}{ρ f} \frac{d _{12} d _{31}}{d _{23}} \frac{Z _{e, 12} Z _{e, 31}}{Z _{e, 23}} e^{j k (d_{12} + d_{31} - d_{23})} e^{α (d_{m 12} + d_{m 31} - d_{m 23})})^{1/2}

with the factor $- j$ that Formula (7) carries and the printed Formula (8) drops (module docstring).

Parameters

Name	Description
`frequencies_hz`	The frequencies, in Hz, increasing.
`electrical_transfer_impedances_ohm`	$Z_{e, 12}$ , $Z_{e, 23}$ and $Z_{e, 31}$ , complex, in Ω.
`diaphragm_distances_m`	$d_{m 12}$ , $d_{m 23}$ and $d_{m 31}$ , in m.
`temperature_c`	The temperature of the air, in °C.
`static_pressure_pa`	The static pressure, in Pa.
`relative_humidity_percent`	The relative humidity, in %.
`acoustic_centres_m`	The acoustic centre of microphones 1, 2 and 3, each relative to its diaphragm on the principal axis, positive in front, in m, one value or one per frequency (Default: the centres of the diaphragms, which Annex A allows at sufficiently remote points).
`dispersion`	Whether $k$ takes the speed of sound with the dispersion of IEC 61094-2 F.3 (Default: `True`).
`corrections_db`	Corrections added to every level (Default: none).
`expanded_uncertainty_db`	The expanded uncertainty, in dB (Default: `None`).

Returns: The ReciprocityCalibration.

Raises

Exception	When
ValueError	for other than three pairs, distances that are not positive or that the acoustic centres use up, or values that are zero or not finite.

free_field_reciprocity_pair

free_field_reciprocity_pair(
    frequencies_hz: ArrayLike,
    electrical_transfer_impedance_ohm: ArrayLike,
    sensitivity_ratio: ArrayLike,
    *,
    diaphragm_distance_m: float,
    temperature_c: float,
    static_pressure_pa: float,
    relative_humidity_percent: float,
    acoustic_centres_m: Sequence[ArrayLike] = (0.0, 0.0),
    dispersion: bool = True,
    corrections_db: Mapping[str, ArrayLike] | None = None,
    expanded_uncertainty_db: ArrayLike | None = None,
) -> ReciprocityCalibration

The complex free-field sensitivities of two microphones and an auxiliary sound source (IEC 61094-3:2016 5.1.3 and 5.7.2, Formula (9) as corrected by COR1).

M_{f, 1} = (- j r_{12} \frac{2 d _{12}}{ρ f} Z_{e, 12} e^{j k d_{12}} e^{α d_{m 12}})^{1/2}

COR1 replaces “modulus of the” by “complex” in 5.7.2, so the formula gives the complex sensitivity; the factor $- j$ is that of Formula (7), which the printed Formula (9) drops (module docstring).

Parameters

Name	Description
`frequencies_hz`	The frequencies, in Hz, increasing.
`electrical_transfer_impedance_ohm`	$Z_{e, 12}$ , complex, in Ω.
`sensitivity_ratio`	$r_{12} = M_{f, 1} / M_{f, 2}$ , complex, measured against the auxiliary source.
`diaphragm_distance_m`	$d_{m 12}$ , in m.
`temperature_c`	The temperature of the air, in °C.
`static_pressure_pa`	The static pressure, in Pa.
`relative_humidity_percent`	The relative humidity, in %.
`acoustic_centres_m`	The acoustic centres of the two microphones, positive in front of the diaphragm, in m (Default: the diaphragms).
`dispersion`	Whether $k$ includes dispersion (Default: `True`).
`corrections_db`	Corrections added to both levels (Default: none).
`expanded_uncertainty_db`	The expanded uncertainty, in dB (Default: `None`).

Returns: The ReciprocityCalibration, of two microphones.

Raises

Exception	When
ValueError	for a distance that is not positive or that the acoustic centres use up, or values that are zero or not finite.

free_field_transfer_impedance

free_field_transfer_impedance(
    frequencies_hz: ArrayLike,
    sensitivity_1_v_per_pa: ArrayLike,
    sensitivity_2_v_per_pa: ArrayLike,
    *,
    diaphragm_distance_m: float,
    temperature_c: float,
    static_pressure_pa: float,
    relative_humidity_percent: float,
    acoustic_centres_m: Sequence[ArrayLike] = (0.0, 0.0),
    dispersion: bool = True,
) -> NDArray[np.complex128]

The electrical transfer impedance two microphones of known free-field sensitivity give (IEC 61094-3:2016 D.4.2, Formula (D.1)).

\frac{U _{2}}{i _{1}} = j \frac{ρ f}{2 d _{12}} M_{f, 1} M_{f, 2} e^{- j k d_{12}} e^{- α d_{m 12}}

Formula (7) turned round. D.4.2 uses it to fill the frequency range below the lowest measured frequency before a transformation to the time domain, with the free-field sensitivities taken there from the pressure sensitivity and the scattering factor (Formula (4)).

Parameters

Name	Description
`frequencies_hz`	The frequencies, in Hz, increasing.
`sensitivity_1_v_per_pa`	$M_{f, 1}$ , complex, in V/Pa.
`sensitivity_2_v_per_pa`	$M_{f, 2}$ , complex, in V/Pa.
`diaphragm_distance_m`	$d_{m 12}$ , in m.
`temperature_c`	The temperature of the air, in °C.
`static_pressure_pa`	The static pressure, in Pa.
`relative_humidity_percent`	The relative humidity, in %.
`acoustic_centres_m`	The two acoustic centres, in m (Default: the diaphragms).
`dispersion`	Whether $k$ includes dispersion (Default: `True`).

Returns: $U_{2} / i_{1}$ , complex, in Ω, at each frequency.

Raises

Exception	When
ValueError	for a distance that is not positive or that the acoustic centres use up, or values that are zero or not finite.

FreeFieldArrangementCheck

FreeFieldArrangementCheck(
    diaphragm_distances_m: tuple[float, ...],
    microphone_diameter_m: float,
    support_length_m: float | None,
    air_attenuation: ReciprocityAirAttenuation,
)

Whether a free-field reciprocity arrangement is the one IEC 61094-3:2016 recommends.

6.4 asks for a distance “great enough” and supporting cylinders “long compared to the diameter”, and puts numbers on both only as recommendations: ten nominal diameters between the microphones (7.3) and twenty along the cylinder (6.4). The verdict holds the arrangement to those numbers, and the conditions to the domain in which B.2 states the accuracy of the attenuation; an arrangement that fails it is not forbidden, but falls outside what the standard recommends and what its uncertainty figures assume.

Built by check_free_field_arrangement. The verdicts are read from the distances, the diameter, the support and the attenuation the check holds, against the numbers 7.3, 6.4, Annex A and B.2 print, so they are not fields.

Attributes

Name	Description
`diaphragm_distances_m`	The distances between the microphones, in m.
`microphone_diameter_m`	The nominal diameter of the microphones, in m.
`support_length_m`	The length of the cylinder each microphone is attached to, in m, or `None`.
`air_attenuation`	The `ReciprocityAirAttenuation` at the frequencies and conditions of the calibration.

FreeFieldArrangementCheck.annex_a_range

property

Every distance is within 150 mm to 500 mm, where Annex A allows the published acoustic centres.

Advisory: it does not enter passes.

FreeFieldArrangementCheck.attenuation_accuracy

property

The conditions and every frequency are within the domain in which B.2 states the accuracy of the attenuation.

FreeFieldArrangementCheck.distances_ok

property

Every distance is greater than ten nominal diameters, as 7.3 recommends.

FreeFieldArrangementCheck.passes

property

The verdict: the distances and the supports are as 7.3 and 6.4 recommend, and the conditions are where B.2 states the accuracy of the attenuation.

FreeFieldArrangementCheck.plot()

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

Plot each distance against ten diameters and the range of Annex A.

Parameters

Name	Description
`ax`	Existing axes to draw on, or `None` to create a figure.
`language`	Label language, `"en"` (default) or `"es"`.
`kwargs`	Forwarded to `barh`.

Returns: The axes. Requires matplotlib (pip install phonometry[plot]).

FreeFieldArrangementCheck.support_ok

property

The support is at least twenty diameters long, as 6.4 recommends, or None.

FreeFieldInputUncertainties

FreeFieldInputUncertainties(
    *,
    u_distance_m: float = 0.0,
    u_acoustic_centre_m: ArrayLike = 0.0,
    u_static_pressure_pa: float = 0.0,
    u_temperature_k: float = 0.0,
    u_relative_humidity_percent: float = 0.0,
    u_air_attenuation_ratio: float = 0.0,
)

The standard uncertainty of each input quantity of the free-field acoustic transfer impedance that free_field_parameter_uncertainty can move: the distance, the three conditions and the air attenuation, rows Table 1 of IEC 61094-3:2016 lists under “Acoustic transfer impedance”, and the acoustic centres of its “Microphone parameters”.

Each one left at zero contributes no component.

Parameters

Name	Description
`u_distance_m`	Of each distance between the diaphragms, in m.
`u_acoustic_centre_m`	Of each acoustic centre, in m, one value or one per frequency (Annex A puts it under 2 mm below the resonance frequency, as a bound). It is held as a read-only float64 copy.
`u_static_pressure_pa`	Of the static pressure, in Pa.
`u_temperature_k`	Of the temperature, in K.
`u_relative_humidity_percent`	Of the relative humidity, in percentage points.
`u_air_attenuation_ratio`	Of the attenuation coefficient, as a fraction of it. B.2 estimates its accuracy at ±10 %, a standard uncertainty of $0, 1/ 3$ for a rectangular distribution.

Raises

Exception	When
ValueError	for an uncertainty that is negative or not finite, or acoustic-centre uncertainties that are not one value or one column.

FreeFieldParameterUncertainty

FreeFieldParameterUncertainty(
    frequencies_hz: NDArray[np.float64],
    components_db: Mapping[str, NDArray[np.float64]],
    microphone: int,
)

The standard uncertainty of a free-field sensitivity level that each parameter of the acoustic transfer impedance contributes (IEC 61094-3:2016 7.8).

Built by free_field_parameter_uncertainty; ready to pass to reciprocity_uncertainty_budget with field="free_field".

Attributes

Name	Description
`frequencies_hz`	The frequencies, in Hz.
`components_db`	The component of each parameter, keyed by its name in `IEC61094_3_TABLE_1`, in dB at each frequency.
`microphone`	The microphone whose level they are for, 1, 2 or 3.

FreeFieldParameterUncertainty.plot()

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

Plot each component against frequency.

Parameters

Name	Description
`ax`	Existing axes to draw on, or `None` to create a figure.
`language`	Label language, `"en"` (default) or `"es"`.
`kwargs`	Forwarded to the first component’s curve.

Returns: The axes. Requires matplotlib (pip install phonometry[plot]).

reciprocity_air_attenuation

reciprocity_air_attenuation(
    frequencies_hz: ArrayLike,
    *,
    temperature_c: float,
    static_pressure_pa: float,
    relative_humidity_percent: float,
) -> ReciprocityAirAttenuation

The air attenuation coefficient of a free-field reciprocity calibration (IEC 61094-3:2016 B.2, Steps 1 to 5).

α = f^{2} [18, 42 \times 1 0^{- 12} (\frac{p _{s}}{p _{s, r}})^{- 1} (\frac{T}{T _{20}})^{1/2} + (\frac{T}{T _{20}})^{- 2} (\frac{4 , 3778}{c} \frac{e ^{- 2239, 1/ T}}{f _{rO} + f ^{2} / f _{rO}} + \frac{36 , 6624}{c} \frac{e ^{- 3352, 0/ T}}{f _{rN} + f ^{2} / f _{rN}})]

in Np/m, with the relaxation frequencies of Step 3 from the water vapour mole fraction of Steps 1 and 2, and $c$ the speed of sound of IEC 61094-2 Formula (F.2) at the conditions. B.2 estimates the accuracy at ±10 % within -20 °C to 50 °C, below 200 kPa, for $0, 5 \times 1 0^{- 3} \leq x_{w} \leq 50 \times 1 0^{- 3}$ and a frequency-to-pressure ratio of 0,4 Hz/kPa to $1 0^{4}$ Hz/kPa (ReciprocityAirAttenuation.within_stated_accuracy).

Step 1 is computed with the coefficient of IEC 61094-2 Table F.2, which it refers to, not with the one it prints (docs/ERRATA.md).

Parameters

Name	Description
`frequencies_hz`	The frequencies, in Hz, increasing.
`temperature_c`	$t$ , in °C.
`static_pressure_pa`	$p_{s}$ , in Pa.
`relative_humidity_percent`	$H$ , in %.

Returns: The ReciprocityAirAttenuation.

Raises

Exception	When
ValueError	for frequencies that are not positive and increasing, a pressure that is not positive, a humidity outside 0 % to 100 %, or a temperature at or below absolute zero.

ReciprocityAirAttenuation

ReciprocityAirAttenuation(
    frequencies_hz: NDArray[np.float64],
    temperature_c: float,
    static_pressure_pa: float,
    relative_humidity_percent: float,
    water_vapour_mole_fraction: float,
    oxygen_relaxation_hz: float,
    nitrogen_relaxation_hz: float,
    speed_of_sound: float,
    classical_np_per_m: NDArray[np.float64],
    oxygen_np_per_m: NDArray[np.float64],
    nitrogen_np_per_m: NDArray[np.float64],
)

The attenuation of sound in air of a free-field reciprocity calibration (IEC 61094-3:2016 7.4 and Annex B), and the speed of sound with dispersion (IEC 61094-2:2009 F.3, NOTE).

Attributes

Name	Description
`frequencies_hz`	The frequencies, in Hz.
`temperature_c`	$t$ , in °C.
`static_pressure_pa`	$p_{s}$ , in Pa.
`relative_humidity_percent`	$H$ , in %.
`water_vapour_mole_fraction`	$x_{w}$ (Step 2).
`oxygen_relaxation_hz`	$f_{rO}$ , in Hz (Step 3).
`nitrogen_relaxation_hz`	$f_{rN}$ , in Hz (Step 3).
`speed_of_sound`	$c$ , the zero-frequency speed of sound of IEC 61094-2 Formula (F.2) at the conditions, in m/s; the one Step 4 divides by.
`classical_np_per_m`	$α_{cl} + α_{rot}$ , in Np/m.
`oxygen_np_per_m`	$α_{vib, O}$ , in Np/m.
`nitrogen_np_per_m`	$α_{vib, N}$ , in Np/m.

ReciprocityAirAttenuation.attenuation_db_per_m

property

$20 l g (e) α$ , in dB/m, the quantity of Table B.1.

ReciprocityAirAttenuation.attenuation_np_per_m

property

$α = α_{cl} + α_{rot} + α_{vib, O} + α_{vib, N}$ (Step 5), in Np/m.

ReciprocityAirAttenuation.dispersive_speed_of_sound

property

The speed of sound at each frequency, in m/s (IEC 61094-2:2009 F.3, NOTE):

c = c_{0} [1 + n \sum \frac{c α _{v n}}{2 π f _{v n}}]

over oxygen and nitrogen, where $c α_{v n}$ does not depend on $c$ because Step 4 divides by it.

ReciprocityAirAttenuation.plot()

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

Plot the attenuation in dB/m and its three parts against frequency.

Parameters

Name	Description
`ax`	Existing axes to draw on, or `None` to create a figure.
`language`	Label language, `"en"` (default) or `"es"`.
`kwargs`	Forwarded to the total-attenuation curve.

Returns: The axes. Requires matplotlib (pip install phonometry[plot]).

ReciprocityAirAttenuation.within_stated_accuracy

property

Whether each frequency is inside the domain in which B.2 states the ±10 % accuracy of the attenuation.

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