noise_control.enclosure_insulation

What an enclosure is worth, measured rather than predicted (ISO 11546).

phonometry.noise_control.enclosures predicts what a box around a machine will do from its walls and its lining. This module is the other half: the measurement that says what the box built actually does, and the arithmetic by which a manufacturer may declare it.

The quantity is a difference of two runs. Determine the machine’s sound power without the enclosure, determine it again with the enclosure in place, and subtract band by band:

That is Equation (1) of both parts, and Equations (2) to (5) are the same subtraction on the A-weighted total, on a sound pressure level at a stated position and, in part 1, on the pair of levels the reciprocity method reads. Nothing here is a transmission loss: an insertion loss carries the source, the room and the mounting with it, which is why the standard makes all three reportable.

ISO 11546-1:1995 measures in a laboratory, for a declaration: the manufacturer’s figure, obtained under conditions the buyer can compare across suppliers. ISO 11546-2:1995 measures the same thing in situ, for an acceptance: the enclosure as installed, in the room it was installed in, with the machine it was built for. The two documents share their definitions, their equations, their reporting rules and their artificial source word for word; what changes is the environment, the base standard the levels come from and, in part 2, an annex that asks whether the room is good enough at all.

Where the machine cannot be run, both parts substitute a source for it, and the substitution is what the choice in applicable_methods is about:

• an actual source, the machine itself, which is the normal case;
• the reciprocity method of part 1, 7.2, which puts the enclosure in a diffuse field and measures inside it, giving $D_{pr}$;
• an artificial source, the tapping machine of Annex A on its undamped steel plate, used at several positions inside the enclosure.

Clause 1 draws the scope around the first of those: the part applies without restriction to a free-standing enclosure smaller than UNRESTRICTED_ENCLOSURE_VOLUME_M3, and a larger one may still be measured with its actual source, provided the base standard’s own limit on volume is met.

Every equation of clauses 6 and 7 is here, with the weighted rating of ISO 717-1 delegated to phonometry.building.weighted_rating rather than re-derived, and the A-weighted estimate of the annexes written so that it cannot disagree with its own inputs: estimated_a_weighted_insulation reduces algebraically to the difference of the two A-weighted totals computed from the same assumed spectrum, which is the only exact oracle either part offers.

Annex A is a hardware drawing and Annex B an illustration; their numbers are constants here and nothing more. Clause 5 is instrumentation, clause 8 hands its uncertainty to the base standard and to ISO 4871, and clauses 9 and 10 are a report. The one piece of clause 9 that computes is the rounding of 9.4, which is EnclosureInsulationResult.rounded.

Neither part prints a worked example, so the tests are anchored where the documents allow: the algebraic identities of the subtraction, the closed form behind Figure C.1 of part 2, which is cross-checked against phonometry.emission.environmental_correction, and the printed thresholds and tables.

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

applicable_methods(
    *,
    condition: EnclosureCondition = 'laboratory',
    source_kind: SourceKind = 'actual',
) -> tuple[MethodEntry, ...]

The rows of Table 1 open to a given condition and source.

Reading the table is what stops a declaration claiming more than its method can give: a survey-grade determination hands back an A-weighted number and nothing per band, so $D_W$ cannot be declared from it, and the reciprocity method exists only in the laboratory.

Parameters

Returns: The rows, as MethodEntry values.

Raises

Constant (float).

ARTIFICIAL_SOURCE_DROP_MM = 40.0

Constant (float).

ARTIFICIAL_SOURCE_EXAMPLE_LWA_DB = 110.0

artificial_source_insulation(
    level_without_by_position: ArrayLike,
    level_with_by_position: ArrayLike,
    *,
    frequencies: ArrayLike | None = None,
    quantity: str = 'sound_power',
    condition: EnclosureCondition = 'laboratory',
    band_fraction: int = 3,
) -> EnclosureInsulationResult

Insertion loss with the tapping source of Annex A, 7.3 of part 1 and 7.2 of part 2.

The plate is dropped at each of several positions, the band difference is formed at each, and the positions are averaged arithmetically: “express the final result as the arithmetic mean value of the results for the different source positions” is the clause’s own sentence, and it is not the energy mean used almost everywhere else in this library, so it is written out here rather than borrowed.

The clause sends the levels to Equation (1) or to Equation (3) depending on which determination was made, so the method yields $D_W$ or $D_p$ and 9.4 e) reports whichever it was. That is quantity.

Parameters

Returns: The averaged insertion loss, as an EnclosureInsulationResult.

Raises

Constant (float).

ARTIFICIAL_SOURCE_LEAK_RATIO_ADVISORY = 0.02

Constant (float).

ARTIFICIAL_SOURCE_MAX_FILL_RATIO = 0.25

Constant (tuple).

ARTIFICIAL_SOURCE_PLATE_MM = (4.0, 800.0, 300.0)

Constant (float).

ARTIFICIAL_SOURCE_STANDOFF_MM = 60.0

EnclosureInsulationResult(
    frequencies: NDArray[np.float64] | None,
    level_without: NDArray[np.float64],
    level_with: NDArray[np.float64],
    insulation: NDArray[np.float64],
    quantity: str,
    a_weighted_insulation: float | None,
    condition: str,
    source_kind: str,
    base_standard: str,
    band_fraction: int,
)

The insertion loss of an enclosure, band by band.

Attributes

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

Draw the two runs and the difference between them.

Requires matplotlib (pip install phonometry[plot]).

Parameters

Returns: The Axes.

EnclosureInsulationResult.rounded() -> NDArray[np.int_]

The band values as clause 9.4 reports them, to the nearest decibel.

The measurement is outside a condition ISO 11546 states.

estimated_a_weighted_insulation(
    spectrum_levels: ArrayLike,
    insulation: ArrayLike,
    *,
    frequencies: ArrayLike,
) -> float

The A-weighted insulation an enclosure would give a stated spectrum.

Annex C of part 1 and Annex D of part 2, the same formula:

where $L_i$ is the assumed source spectrum, $A_i$ the A-weighting of the band and $D_i$ the measured insulation. The sign of $A_i$ is the trap: the standard prints an attenuation, positive where the weighting takes level away, while this library’s band corrections are the correction itself, so $A_i=-C_k$. Both terms are formed here from the same table, so the total and the sum cannot disagree, and with $D_i=0$ the answer is exactly zero.

The same formula serves $D_W$ (giving $D_{WA,e}$), $D_p$ and $D_{pr}$; which one it is, is the caller’s.

Parameters

Returns: $D_{WA,e}$, in decibels.

Raises

fill_ratio(source_volume_m3: float, interior_volume_m3: float) -> float

How much of the enclosure the source fills, 3.15 of part 1 and 3.13 of part 2.

$\varphi =V_S/V_E$. The artificial source of Annex A is representative only up to ARTIFICIAL_SOURCE_MAX_FILL_RATIO; past that it is changing the interior field it is supposed to be measuring through.

Parameters

Returns: The ratio, dimensionless.

Raises

leak_ratio(opening_area_m2: float, interior_surface_area_m2: float) -> float

How open an enclosure or a cabin is.

$\theta =S_O/S_E$, the area of the openings over the area of the interior surface: definition 3.16 of ISO 11546-1, 3.14 of ISO 11546-2 and 3.14 of ISO 11957, in the same words in all three. What they do with it differs: clause 4 of ISO 11546 only prefers a value under 2 %, while clause 1 of ISO 11957 makes the same 2 % a condition of applicability.

An opening fitted with an effective silencer does not count as one.

Parameters

Returns: The ratio, dimensionless.

Raises

Constant (mapping).

MANDATORY_BAND_RANGE_HZ = {3: (100.0, 5000.0), 1: (125.0, 4000.0)}

MethodEntry(
    base_standard: str,
    test_environment: str,
    quantities: tuple[str, ...],
    subclause: str,
    band_values: bool,
    survey_grade_excluded: bool = False,
)

One row of Table 1: a way of measuring and what it yields.

Attributes

Constant (mapping).

PREFERRED_BAND_RANGE_HZ = {3: (50.0, 10000.0), 1: (63.0, 8000.0)}

reciprocity_insulation(
    external_levels: ArrayLike,
    internal_levels: ArrayLike,
    *,
    frequencies: ArrayLike | None = None,
    band_fraction: int = 3,
) -> EnclosureInsulationResult

Insertion loss measured from the outside in, Equation (5) of part 1.

$D_{pr}=\overline{L_{p,\text{ext}}}-\overline{L_{p,\text{int}}}$: the enclosure is put in a diffuse field, the field is measured around it and again inside it, and the difference is the insulation the enclosure would give a source within it. The method belongs to the laboratory, and it is the one case where the enclosure is measured without any source inside at all.

Parameters

Returns: The insertion loss, as an EnclosureInsulationResult whose quantity is "reciprocity".

Raises

Constant (mapping).

ROOM_ABSORPTION_ESTIMATES = {0.05: 'Nearly empty room with smooth hard walls made of concrete, brick, plaster or tile', 0.1: 'Partly empty room; room with smooth walls', 0.15: 'Room with furniture; rectangular machinery room; rectangular industrial room', 0.2: 'Irregularly shaped room with furniture; irregularly shaped machinery room or industrial room', 0.25: 'Room with upholstered furniture; machinery or industrial room with a small amount of sound-absorbing material on ceiling or walls (e.g. partially absorptive ceiling)', 0.35: 'Room with sound-absorbing materials on both ceiling and walls', 0.5: 'Room with large amounts of sound-absorbing materials on ceiling and walls'}

seal_ratio(leak: float) -> float

The reciprocal of the leak ratio.

$\psi =1/\theta$, from NOTE 5 to definition 3.16 of ISO 11546-1 and NOTE 3 to definition 3.14 of ISO 11957. Both print the two because a catalogue quotes whichever reads better.

Parameters

Returns: $\psi$, dimensionless.

Raises

sound_power_insulation(
    level_without: ArrayLike,
    level_with: ArrayLike,
    *,
    frequencies: ArrayLike | None = None,
    a_weighted_without: float | None = None,
    a_weighted_with: float | None = None,
    base_standard: str = 'ISO 3744',
    condition: EnclosureCondition = 'laboratory',
    source_kind: SourceKind = 'actual',
    band_fraction: int = 3,
) -> EnclosureInsulationResult

Insertion loss from two sound power determinations, Equations (1) and (2).

$D_W=L_{W,\text{without}}-L_{W,\text{with}}$ band by band, and $D_{WA}$ the same difference of the A-weighted totals. Where the A-weighted pair is not supplied it is computed from the band spectra with the ISO 3744 Annex E table, which is what the note to clause 6.2 prefers.

Parameters

Returns: The insertion loss, as an EnclosureInsulationResult.

Raises

sound_pressure_insulation(
    level_without: ArrayLike,
    level_with: ArrayLike,
    *,
    frequencies: ArrayLike | None = None,
    a_weighted_without: float | None = None,
    a_weighted_with: float | None = None,
    base_standard: str = 'ISO 11201',
    condition: EnclosureCondition = 'laboratory',
    source_kind: SourceKind = 'actual',
    band_fraction: int = 3,
) -> EnclosureInsulationResult

Insertion loss from two sound pressure levels, Equations (3) and (4).

$D_p=L_{p,\text{without}}-L_{p,\text{with}}$ at one stated position, with the same microphone positions in both runs, and $D_{pA}$ the difference of the A-weighted values. The position is part of the answer: the standard requires it in the report, because an insertion loss at the operator’s ear and one a metre from the panel are different numbers about the same enclosure.

Parameters

Returns: The insertion loss, as an EnclosureInsulationResult.

Raises

source_position_clearance_m(shortest_inner_dimension_m: float) -> float

How far the artificial source stands from a wall, 7.3 of part 1 and 7.2 of part 2.

$0,2d$ with $d$ the shortest interior dimension of the enclosure, so that the plate is never against a panel it is meant to excite through the air. Both parts print the same sentence, and both add that the source is used in two orientations 90 degrees apart where the enclosure has room for them.

Parameters

Returns: The least distance to any wall, in metres.

Raises

Constant (float).

SOURCE_WALL_CLEARANCE_FACTOR = 0.2

test_environment_applicability(
    *,
    base_standard: str,
    mean_absorption_coefficient: float,
    room_surface_area_m2: float,
    measurement_surface_area_m2: float,
) -> TestEnvironmentApplicability

Is this room good enough for that base standard? Annex C of part 2.

Annex C asks the question the other way round from the emission standards: not what the environmental correction of this room is, but how much room a method needs. With $K_2=10\lg (1+4S/(\alpha S_V))$ held at the limit Table C.1 sets, the ratio the room must reach is

which is Figure C.1 in closed form, the curve the annex asks the reader to read off by eye. Take $\alpha$ from ROOM_ABSORPTION_ESTIMATES when nobody measured it.

A standard that works by comparison with a reference sound source, ISO 3743-1 and ISO 3747, states no $K_2$ requirement at all; for those the answer carries the background margin and nothing else, and applicable is decided by the margin alone, which this function does not see. It is reported as True there, with required_area_ratio at None, so that the caller reads the table rather than a number the annex does not give.

Parameters

Returns: The verdict, as a TestEnvironmentApplicability.

Raises

Constant (mapping).

TEST_ENVIRONMENT_REQUIREMENTS = {'ISO 3743-1': (None, 6.0), 'ISO 3744': (2.0, 6.0), 'ISO 3746': (7.0, 3.0), 'ISO 3747': (None, 3.0), 'ISO 9614-1': (None, None), 'ISO 9614-2': (None, None), 'ISO 11201': (2.0, 6.0), 'ISO 11202': (7.0, 3.0), 'ISO 11204': (7.0, 6.0)}

TestEnvironmentApplicability(
    base_standard: str,
    environmental_correction_limit_db: float | None,
    background_margin_limit_db: float | None,
    required_area_ratio: float | None,
    actual_area_ratio: float,
    applicable: bool,
    mean_absorption_coefficient: float,
)

Whether a room is good enough for a base standard, Annex C of part 2.

Attributes

Constant (float).

UNRESTRICTED_ENCLOSURE_VOLUME_M3 = 2.0

weighted_insulation(
    insulation: ArrayLike,
    *,
    quantity: str = 'sound_power',
    band_fraction: int = 3,
) -> WeightedEnclosureInsulation

The single-number rating of an insertion loss, 7.4 of part 1 and 7.3 of part 2.

Both parts say the same thing: rate the spectrum by ISO 717-1, putting $D_W$ or $D_{pr}$ where that standard writes $R$. The reference curve, the shift and the adaptation terms come from phonometry.building.weighted_rating, which has its own conformance rows; what is done here is the trim to the rating bands.

Parameters

Returns: The rating, as a WeightedEnclosureInsulation.

Raises

WeightedEnclosureInsulation(
    rating: int,
    c: int,
    ctr: int,
    unfavourable_sum: float,
    band_centres_hz: NDArray[np.float64],
    quantity: str,
)

The single-number rating of an insertion loss spectrum, ISO 717-1.

Attributes