metrology.reference_values
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.
Preferred reference values for acoustical and vibratory levels (ISO 1683:2015).
A level in decibels is a ratio to a reference value, so the number means nothing until the reference is known: the same pressure reads 26 dB higher against the 1 µPa of water than against the 20 µPa of air, and the same vibration 34 dB higher against 1 nm/s than against 50 nm/s. ISO 1683:2015 fixes one reference per quantity in three tables, and the level functions of this library count their decibels from them unless the standard they implement names another:
- Table 1, sounds in air and other gases: sound pressure 20 µPa, sound exposure (20 µPa)² s, sound power 1 pW, sound energy 1 pJ and sound intensity 1 pW/m².
- Table 2, sounds in water and other liquids: sound pressure 1 µPa, sound exposure 1 µPa² s, sound power 1 pW, sound energy 1 pJ, sound intensity 1 pW/m², sound particle displacement 1 pm, velocity 1 nm/s and acceleration 1 µm/s², and a distance of 1 m for the compound quantities of its note c (a source level re 1 µPa m, for one).
- Table 3, vibratory quantities: displacement 1 pm, velocity 1 nm/s, acceleration 1 µm/s² and force 1 µN. Its note b adds the 50 nm/s that is also used for structure-borne sound, against which the velocity level comes out close to the associated sound pressure and intensity levels.
ISO1683_REFERENCE_VALUES holds all of them, keyed by medium and then
by quantity, and every value is in the coherent SI unit its row names, so the
20 µPa of air is 2e-05 Pa:
from phonometry import metrology
p0 = metrology.ISO1683_REFERENCE_VALUES["gas"]["sound_pressure"]p0.value, p0.unit, p0.printed # (2e-05, 'Pa', '20 µPa')Note b of Table 2 gives the offset between the two pressure references, a
level re 1 µPa being dB above the same
pressure re 20 µPa; phonometry.underwater.in_air_to_underwater_spl
applies it.
The values were transcribed from the Spanish text UNE-EN ISO 1683:2016, which
adopts ISO 1683:2015 unchanged, PDF pages 8 and 9 (printed folios 8 and 9),
and the quantity names are given here in English. A module that counts its
decibels from a different reference keeps it, and names the document it comes
from beside it: DIN 45672-2 defines its own 5·10⁻⁸ m/s for railway vibration
(Formula (2)), and ISO/TS 7849 and ISO 9611 refer the surface velocity to the
same 5·10⁻⁸ m/s, which is the 50 nm/s of note b of Table 3.
scripts/check_reference_values.py holds the tree to that: a reference value
declared in the package either points at this table or says where it was read.
Auto-generated from the source docstrings by
scripts/generate_api_docs.py(make api-docs). Do not edit by hand.
ISO1683_REFERENCE_VALUES
Section titled “ISO1683_REFERENCE_VALUES”Constant (mapping).
ReferenceValue
Section titled “ReferenceValue”ReferenceValue( quantity: str, medium: str, value: float, unit: str, printed: str, table: str,)One reference value of ISO 1683:2015, with what it is a reference of.
Attributes
| Name | Description |
|---|---|
quantity | The quantity the value is the reference of, in English ("sound pressure", "vibratory velocity"). |
medium | "gas" (Table 1), "liquid" (Table 2) or "solid" (Table 3, structure-borne sound and vibration). |
value | The reference value, in the coherent SI unit unit names: 20 µPa is 2e-05 with unit "Pa". |
unit | The SI unit of value. |
printed | The value as the table prints it, prefix and all. |
table | Where the value is printed: "Table 1" to "Table 3", or "Table 3, note b" for the 50 nm/s alternative. |