solids.plateau

The three numbers a panel needs before its transmission loss can be sketched.

A single panel does not attenuate sound the way the mass law says it does. The mass law is a straight line rising six decibels an octave, and a real panel leaves it twice: once at the bottom, where the panel is stiff and resonant rather than limp, and once near the coincidence frequency, where a bending wave in the panel and a sound wave in the air travel at the same speed along the surface and the panel stops resisting at all. Between those two departures the curve flattens into a plateau.

The plateau method is the cheap way to draw that shape. Rather than solving the plate model, it places the plateau from three numbers that depend only on what the panel is made of: how much mass a millimetre of it brings, how high the plateau sits, and how wide it is in frequency. Norton & Karczub draw the mass law first, then “the coincidence region is approximated by a horizontal line whose height is obtained from Table 3.1”; the plateau starts where that line meets the mass law, at a frequency A, ends at B, which the frequency ratio places relative to A, and above B the curve rises at 10 dB per octave. This module holds those three numbers, for the eight materials the table lists, and phonometry.building.plateau_transmission_loss draws the curve from them: its building.PLATEAU_MATERIALS is built from the rows here, so the table is typed once.

PlateauMaterial.surface_density_per_mm_kg_m2 is kilograms per square metre per millimetre of thickness, which is the material’s density divided by a thousand. Aluminium’s 2.66 is 2660 kg/m3. It is held in the unit the page prints rather than converted to a density, because the method is applied with it in that form: multiply by the thickness in millimetres and the surface density of the panel falls out. Converting it would make a caller divide by a thousand again at the point of use, and a catalogue that stores a quantity in a unit nobody uses it in has made the reader’s work harder to look tidier.

It is not a transmission loss spectrum. One of the three numbers is a transmission loss, PlateauMaterial.coincidence_height_db, the level of the plateau in decibels, and it holds only over the plateau and only as the method’s approximation to it. The measured and tabulated insulation of real constructions lives in PUBLISHED_TRANSMISSION_LOSS, and the duct walls in PUBLISHED_DUCT_TRANSMISSION_LOSS.

In solids/data/norton-karczub-2003-table-3-1.json, read at import through the package-data reader in phonometry._internal, the same as every other catalogue here.

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

plateau_material_named(name: str) -> tuple[PlateauMaterial, ...]

Every row whose printed name contains name, case insensitively.

Parameters

Returns: The matching rows, in the order the tables list them. Empty when nothing matches, which is not an error: a caller asking whether a material is tabulated gets an empty answer rather than an exception.

PlateauMaterial(
    *,
    name: str,
    source: str,
    table: str = '',
    variant: str = '',
    basis: Mapping[str, str] = ...,
    approximate: frozenset[str] = frozenset(),
    derived: Mapping[str, str] = ...,
    converted: Mapping[str, tuple[str, str]] = ...,
    carried: Mapping[str, str] = ...,
    ranges: Mapping[str, tuple[float | None, float | None]] = ...,
    bounded_above: frozenset[str] = frozenset(),
    bounded_below: frozenset[str] = frozenset(),
    reported: Mapping[str, tuple[float | tuple[float, float], ...]] = ...,
    unquantified: Mapping[str, str] = ...,
    uncertainty: Mapping[str, float] = ...,
    not_derivable: Mapping[str, str] = ...,
    misprinted: Mapping[str, str] = ...,
    attributed_to: Mapping[str, str] = ...,
    group: str = '',
    note: str = '',
    surface_density_per_mm_kg_m2: float | None = None,
    coincidence_height_db: float | None = None,
    plateau_frequency_ratio: float | None = None,
)

One material’s plateau-method constants, as a page printed them.

Attributes

PlateauMaterial.basis_of(field_name: str) -> str

What the source says this field is, one of CATALOGUE_BASES.

The five are measured, declared, calculated, estimated and extended.

Parameters

Returns: The field’s own entry in basis, else the row’s, else the empty string, which means the source does not say.

classmethod

PlateauMaterial.from_printed(**cells: Any) -> Self

A row built from the cells its page prints, completed and marked.

The one path that works anything out. The cells are what the page prints, under the field names of the class and with the hedges each cell carries, as a data file writes them. A figure written under a unit the class takes as an alias of its own (an AbsorptionAreaSpectrum takes absorption_area_125_ft2 for absorption_area_125_m2) is converted on its digits with an exact factor and rounded once, and converted records the figure and its unit. The row is then built and held to the contract the class docstring lists, so every cell is checked before any arithmetic reads it. Last, the class fills what follows from those cells (a modulus from a plate speed, a density and a Poisson ratio), never over a cell that holds a value or one the row says something else about, and derived says how each filled value was reached and, when the cells it rests on do not share one basis, the basis of each. Cells the arithmetic cannot take are refused rather than turned into a value that would be wrong: a modulus of 1 GPa and a shear modulus of 0.1 GPa give a Poisson ratio of 4, which no isotropic solid has, and a row whose cells are not meant to give a value says so in not_derivable, which keeps the arithmetic from running.

Cls(...) stays literal: it holds what it is given and works nothing out. To change a cell of a row and have what follows from it follow again, change it in printed_fields and build again here; dataclasses.replace would copy the derived values as they were:

cells = row.printed_fields()
cells["density_kg_m3"] = 2400.0
row = type(row).from_printed(**cells)

Parameters

Returns: The row, with what follows from its cells filled in.

Raises

PlateauMaterial.is_approximate(field_name: str) -> bool

Whether the page prints this field with a ~.

Parameters

Returns: True when the page rounded the cell on purpose.

PlateauMaterial.is_derived(field_name: str) -> bool

Whether this library computed this field instead of reading it.

Parameters

Returns: True when the page did not print it and the value follows from cells that it did. derived says how. A value the page prints in another unit, or gives by reference to another of its rows, answers False: the number is the page’s, and converted or carried says so.

PlateauMaterial.printed(
    field_name: str,
    *,
    wanted_by: str = 'the caller',
) -> float

One quantity this page prints, or a refusal that says what it had.

Every quantity of a row is optional, because the pages print different columns, so a caller passing one into a function that requires a float has to narrow it. Doing it here beats an assertion at each call site: the refusal names the field, who wanted it and what the page had in that cell, which is the difference between a cell the book left empty and a cell holding the word “model”.

Parameters

Returns: The value, as a float.

Raises

PlateauMaterial.printed_fields() -> dict[str, Any]

The cells the page prints, as from_printed takes them.

Every field, the name, the citation, the table and every hedge included, except the values this library derived, derived itself, and a field left at a default that holds nothing (a quantity the page leaves out, an empty text or hedge). A text field whose default says something is kept even when it holds no text: the per of an area per unit is a person unless the row says otherwise, and a row that leaves it empty has said otherwise. A value converted from the page’s unit and one the page gives by reference to another of its rows are the page’s, so they stay, with converted and carried beside them.

For every row from_printed builds, and so for every packaged one, type(row).from_printed(**row.printed_fields()) is the row again, and changing a cell before building it again is how a row is edited without carrying a derived value that no longer follows from it. A derived passed to the literal constructor is the caller’s own; it is left out here with its value, like every derived one, so building again gives back only what the class works out.

Returns: A new dictionary of constructor keywords. The values are the ones the row holds, frozen as the row holds them.

PlateauMaterial.why_missing(field_name: str) -> str

Why this field is None, in the page’s own terms.

A catalogue that answers None and stops is asking the caller to guess whether the material has no such property, whether the book measured it and printed a dash, or whether the cell holds something that is not a number. Each of those is a different answer.

Parameters

Returns: What the page had in that cell, or the empty string when the field is not missing at all. A field the page has no column for and this library cannot derive, because the cells it would need are themselves a range, answers that it does not follow.

Raises

Constant (mapping).