acoustics/quantities

VocabularyAcousticsDraft32 terms

Acoustic quantities. Attenuation terms are in decibels and positive when they reduce the level, as ISO 9613-2; a gain is a negative attenuation.

Used by Axis, Criterion, Emission, Evidence, Property, Step and Trace.

Level

  • sound_power_levelL_W

    Sound power level

    UnitdBValuenumber

    The sound power level, re 1 pW, Z-weighted.

  • a_weighted_sound_power_levelL_WA

    A-weighted sound power level

    UnitdBValuenumber

    The A-weighted sound power level, re 1 pW.

  • sound_pressure_levelL_p

    Sound pressure level

    UnitdBValuenumber

    The sound pressure level, re 20 µPa, Z-weighted.

  • a_weighted_sound_pressure_levelL_pA

    A-weighted sound pressure level

    UnitdBValuenumber

    The A-weighted sound pressure level, re 20 µPa.

  • c_weighted_sound_pressure_levelL_pC

    C-weighted sound pressure level

    UnitdBValuenumber

    The C-weighted sound pressure level, re 20 µPa.

  • directivityD_c

    Directivity

    UnitdBValuenumber

    The directivity correction of a source toward a path.

    ISO 9613-2:2024

Propagation

  • geometric_divergenceA_div

    Geometric divergence

    UnitdBValuenumber

    Attenuation by geometric divergence: 20 log10(d) + 11 dB for a point source.

    ISO 9613-2:2024

  • atmospheric_absorptionA_atm

    Atmospheric absorption

    UnitdBValuenumber

    Attenuation by atmospheric absorption, from temperature, humidity and pressure, as ISO 9613-1.

    ISO 9613-2:2024

  • ground_attenuationA_gr

    Ground attenuation

    UnitdBValuenumber

    Attenuation by the ground effect.

    ISO 9613-2:2024

  • ground_attenuation_sourceA_s

    Ground attenuation, source region

    UnitdBValuenumber

    The ground effect of the source region.

    ISO 9613-2:2024

  • ground_attenuation_middleA_m

    Ground attenuation, middle region

    UnitdBValuenumber

    The ground effect of the middle region.

    ISO 9613-2:2024

  • ground_attenuation_receiverA_r

    Ground attenuation, receiver region

    UnitdBValuenumber

    The ground effect of the receiver region.

    ISO 9613-2:2024

  • screeningA_bar

    Screening

    UnitdBValuenumber

    Attenuation by a barrier, a building or the terrain.

    ISO 9613-2:2024

  • foliage_attenuationA_fol

    Foliage attenuation

    UnitdBValuenumber

    Attenuation by foliage.

    ISO 9613-2:2024

  • industrial_site_attenuationA_site

    Industrial site attenuation

    UnitdBValuenumber

    Attenuation by installations on an industrial site.

    ISO 9613-2:2024

  • housing_attenuationA_hous

    Housing attenuation

    UnitdBValuenumber

    Attenuation by housing.

    ISO 9613-2:2024

  • meteorological_correctionC_met

    Meteorological correction

    UnitdBValuenumber

    The correction for long-term average weather.

    ISO 9613-2:2024

  • reflection_loss

    Reflection loss

    UnitdBValuenumber

    Attenuation by absorption at a reflecting surface, for one reflected path.

  • excess_attenuation

    Excess attenuation

    UnitdBValuenumber

    Everything the ground and the air do beyond divergence and absorption: the level re the free field at the direct distance, with its sign changed. In a wave-field run it holds the ground, refraction, terrain and obstacles together.

  • excess_attenuation_flat

    Excess attenuation over flat ground

    UnitdBValuenumber

    The excess attenuation over flat ground in still air: the ground effect alone.

  • refraction_attenuation

    Refraction attenuation

    UnitdBValuenumber

    The excess attenuation less that of the same run in still air. A difference of two runs; it does not add up with the other differences.

  • obstacle_attenuation

    Obstacle attenuation

    UnitdBValuenumber

    The excess attenuation less that of the same run without its obstacles. A difference of two runs.

  • terrain_attenuation

    Terrain attenuation

    UnitdBValuenumber

    The excess attenuation less that of the same run over flat ground. A difference of two runs.

  • scattered_levelL_scat

    Scattered level

    UnitdBValuenumber

    The level that turbulence scatters into the receiver point, re the free field.

  • free_field_pressure_ratio

    Pressure re the free field

    Unit1Valuenumber

    The complex sound pressure at a point divided by the free-field pressure at the same direct distance: the field a wave-field method gives. Its size in decibels, 20 log10 of its magnitude, is the level re the free field, the negative of the excess attenuation. Inline it lies along a complex_part axis; in a file it is complex64 or complex128.

  • atmospheric_absorption_coefficientα

    Atmospheric absorption coefficient

    UnitdB/kmValuenumberRangeat least 0

    Attenuation by the air per kilometre, by frequency.

    ISO 9613-1:1993

Ground

  • ground_factorG

    Ground factor

    Unit1ValuenumberRange0 to 1

    The share of porous ground: 0 hard, 1 porous.

    ISO 9613-2:2024

  • flow_resistivityσ

    Flow resistivity

    UnitkPa.s/m2ValuenumberRangeat least 0

    The effective flow resistivity of the ground.

Surface

  • absorption_coefficientα

    Absorption coefficient

    Unit1ValuenumberRange0 to 1

    The share of incident sound power a surface absorbs, by frequency.

  • transmission_lossR

    Transmission loss

    UnitdBValuenumber

    The level difference across a wall or an enclosure, by frequency.

Air

  • sound_speedc

    Sound speed

    Unitm/sValuenumberRangeat least 0

    The speed of sound in the air. A propagation method that fixes it states it here, apart from the temperature that sets the air absorption.

Source

  • face_height

    Face height

    UnitmValuenumberRangeat least 0

    The height of a vertical area source's face, from its bottom edge to its top edge. A source whose geometry is a line and that states a face height radiates from the upright face over that line; its location's height is the face's middle.