emission.vibration_sound_power

Airborne sound power from surface vibration (ISO/TS 7849-1/-2:2009).

The airborne sound power a machine radiates through the structure-borne vibration of its outer surface is estimated from the surface vibratory velocity and a radiation factor epsilon (the radiation efficiency). The radiated power is (ISO/TS 7849-1, Equation 6):

P = Z_c * <v**2> * S * epsilon                              [W]

with Z_c the characteristic impedance of air, <v**2> the mean-square vibratory velocity averaged over the radiating area S. The vibratory velocity is reported as a level re v0 = 5e-8 m/s (Equation 3):

L_v = 10 lg(<v**2> / v0**2) = 20 lg(v / v0)                 [dB]

so the A-weighted sound power level follows in logarithmic form (ISO/TS 7849-1, Equation 12; ISO/TS 7849-2, Equation 15):

L_W = L_v + 10 lg(S / S0) + 10 lg(epsilon) + 10 lg(Z_c,n / Z_c,0)   [dB]

where S0 = 1 m2, the normalized characteristic impedance Z_c,n = 411 N.s/m3 (at 23 degC, 101,3 kPa) and the reference acoustic impedance Z_c,0 = 400 N.s/m3 give the fixed 10 lg(411/400) = 0,118 dB term.

The two parts differ only in epsilon:

• Part 1 (survey) assumes epsilon = 1 and yields the upper limit L_W,max of the radiated power, needing only <v**2> and S.
• Part 2 (engineering) applies a frequency-band radiation factor epsilon_j determined (per ISO 9614) as epsilon_j = P_j / (Z_c,n <v_j**2> S) (Equation 8).

This module feeds the structure-borne source characterisation standards (ISO 9611, EN 15657, EN 12354-5).

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

extraneous_velocity_correction

extraneous_velocity_correction(level_difference: float) -> float

Correction K1A for extraneous vibration (ISO/TS 7849-1, Table 2).

dLv is the difference between the operating and the extraneous vibratory velocity levels. The correction is subtracted from the measured level; per the standard dLv >= 10 dB gives 0 dB, and dLv < 3 dB uses the 3 dB value (the result is then an upper boundary). The level difference is rounded to the nearest integer decibel to index the standard’s table.

Parameters

Name	Description
level_difference	Level difference dLv, in dB.

Returns: The correction K1A to subtract, in dB.

mean_velocity_level

mean_velocity_level(
    levels: ArrayLike,
    areas: ArrayLike | None = None,
) -> float

Mean vibratory velocity level over the surface (ISO/TS 7849-1, Eq. 10/11).

With uniformly distributed positions (areas is None) this is the energetic average (Equation 10); with per-position partial areas it is the area-weighted average (Equation 11).

Parameters

Name	Description
levels	Velocity levels L_v,i at the positions, in dB.
areas	Partial areas S_i (Equation 11), or None for the uniform energetic average (Equation 10).

Returns: The mean velocity level, in dB.

NORMALIZED_IMPEDANCE

Constant (float).

NORMALIZED_IMPEDANCE = 411.0

radiated_sound_power_level

radiated_sound_power_level(
    velocity_level: ArrayLike,
    area: float,
    *,
    radiation_factor: ArrayLike = 1.0,
    reference_area: float = 1.0,
    normalized_impedance: float = 411.0,
    reference_impedance: float = 400.0,
) -> np.ndarray

Radiated sound power level (ISO/TS 7849-1 Eq. 12, -2 Eq. 15).

L_W = L_v + 10 lg(S/S0) + 10 lg(epsilon) + 10 lg(Z_c,n/Z_c,0). With the default radiation_factor = 1 this is the Part 1 upper limit L_W,max; pass a measured epsilon for the Part 2 engineering value.

Parameters

Name	Description
velocity_level	Mean vibratory velocity level L_v (scalar or array, e.g. per band), in dB re 5e-8 m/s.
area	Radiating surface area S, in m^2 (> 0).
radiation_factor	Radiation factor epsilon (Default: 1.0).
reference_area	Reference area S0 (Default: 1 m^2).
normalized_impedance	Z_c,n (Default: 411 N.s/m^3).
reference_impedance	Z_c,0 (Default: 400 N.s/m^3).

Returns: The sound power level L_W, in dB re 1 pW.

Raises

Exception	When
ValueError	for a non-positive area, reference area or impedance.

radiation_factor

radiation_factor(
    sound_power: ArrayLike,
    area: float,
    mean_square_velocity: ArrayLike,
    *,
    impedance: float = 411.0,
) -> np.ndarray

A-weighted radiation factor epsilon (ISO/TS 7849-1 Eq. 4, -2 Eq. 8).

epsilon = P / (Z_c <v**2> S), the sound-radiation efficiency, from an independently measured radiated power (ISO 9614), the surface area and the mean-square vibratory velocity.

Parameters

Name	Description
sound_power	Radiated airborne sound power P (scalar or array), in W.
area	Radiating surface area S, in m^2 (> 0).
mean_square_velocity	Mean-square vibratory velocity <v**2>, in (m/s)^2.
impedance	Characteristic impedance Z_c (Default: 411 N.s/m^3).

Returns: The radiation factor epsilon (dimensionless).

Raises

Exception	When
ValueError	for a non-positive area or impedance.

REFERENCE_VELOCITY

Constant (float).

REFERENCE_VELOCITY = 5e-08

sound_power_from_vibration

sound_power_from_vibration(
    velocity_level: ArrayLike,
    area: float,
    *,
    radiation_factor: ArrayLike = 1.0,
    frequencies: ArrayLike | None = None,
) -> VibrationSoundPowerResult

Bundle a sound-power-from-vibration determination (ISO/TS 7849).

Parameters

Name	Description
velocity_level	Mean vibratory velocity level L_v (per band), dB.
area	Radiating surface area S, in m^2 (> 0).
radiation_factor	Radiation factor epsilon (Default: 1.0 -> the Part 1 upper limit); scalar or per band.
frequencies	Band centre frequencies, in hertz, or None.

Returns: The VibrationSoundPowerResult.

velocity_level

velocity_level(
    velocity: ArrayLike,
    *,
    reference: float = 5e-08,
) -> np.ndarray

Vibratory velocity level L_v = 20 lg(v/v0) (ISO/TS 7849-1, Eq. 3).

Parameters

Name	Description
velocity	R.m.s. vibratory velocity v (scalar or array), in m/s.
reference	Reference velocity v0 (Default: 5e-8 m/s).

Returns: The velocity level L_v, in dB re v0.

Raises

Exception	When
ValueError	for a non-positive reference.

velocity_level_from_acceleration

velocity_level_from_acceleration(
    peak_acceleration: ArrayLike,
    frequency: ArrayLike,
    *,
    reference: float = 5e-08,
) -> np.ndarray

Velocity level from a sinusoidal acceleration (ISO/TS 7849-1, Eq. 8).

L_v = 20 lg( a_peak / (2 pi f v0 sqrt(2)) ), used to convert a calibration acceleration to the equivalent r.m.s. velocity level.

Parameters

Name	Description
peak_acceleration	Peak acceleration a_peak (scalar or array), in m/s^2.
frequency	Frequency f, in hertz.
reference	Reference velocity v0 (Default: 5e-8 m/s).

Returns: The velocity level L_v, in dB re v0.

Raises

Exception	When
ValueError	for a non-positive frequency or reference.

VibrationSoundPowerResult

VibrationSoundPowerResult(
    velocity_level: np.ndarray,
    sound_power_level: np.ndarray,
    radiation_factor: np.ndarray,
    area: float,
    frequencies: np.ndarray | None = None,
)

Sound power radiated by surface vibration (ISO/TS 7849).

Attributes

Name	Description
frequencies	Band centre frequencies, in hertz, or None for a single broadband value.
velocity_level	Mean vibratory velocity level L_v per band, in dB.
sound_power_level	Radiated sound power level L_W per band, in dB.
radiation_factor	Radiation factor epsilon per band.
area	Radiating surface area S, in m^2.

VibrationSoundPowerResult.plot()

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

Plot the radiated sound power level per band.

Requires matplotlib (pip install phonometry[plot]); returns the Axes.

VibrationSoundPowerResult.report()

VibrationSoundPowerResult.report(
    path: str,
    *,
    metadata: ReportMetadata | None = None,
    engine: str = 'reportlab',
    verbose: bool = False,
    language: str = 'en',
) -> str

Render an ISO/TS 7849 sound-power-from-vibration determination fiche.

Writes a one-page sound-power test sheet: the standard-basis line naming the vibration method (the ISO/TS 7849-1 survey method with a fixed radiation factor when every band uses epsilon = 1, otherwise the ISO/TS 7849-2 engineering method with a determined radiation factor), an optional metadata header (client, machine/source, test environment, instrumentation, climate, date), a per-band table (nominal octave/one-third-octave frequency, the surface vibratory velocity level Lv and the radiated band sound-power level LW), the sound-power spectrum LW(f) with a nominal band axis, the boxed A-weighted sound power level LWA (dB re 1 pW) with the total LW, the radiating area S and the applied method, an optional verdict row against a declared limit, and a measurement-basis strip stating the sound-power relation LW = Lv + 10 lg(S/S0) + 10 lg(epsilon) + 10 lg(Zc,n/Zc,0).

Parameters

Name	Description
path	Destination path of the PDF file.
metadata	Optional ReportMetadata supplying the header (client, specimen the machine/source, test_room the test environment, instrumentation, temperature, relative_humidity, pressure, test_date), the footer identity (laboratory, operator, report_id, notes) and, via requirement, a declared A-weighted sound-power limit the fiche checks the result against (lower is better). The radiating area S comes from the result itself.
engine	Rendering back end; only "reportlab" is supported.
verbose	When True the per-band table adds the radiation factor epsilon column.
language	Fiche language: "en" (default) or "es".

Returns: The written path as a str.

Raises

Exception	When
ValueError	If engine is not "reportlab" or language is unknown.
ImportError	If reportlab (or, for the figure, matplotlib) is not installed (pip install phonometry[report]).

VibrationSoundPowerResult.sound_power_level_a

property

A-weighted sound power level L_WA, in dB re 1 pW.

Combines the band levels with the A-weighting band corrections of ISO 3744:2010 Annex E (the standard tabulation reused by the vibration method) when band centre frequencies are known. Without band frequencies the result is an unweighted broadband level that cannot be A-weighted, so L_WA is undefined and nan is returned (the report then boxes the unweighted total L_W instead of an L_WA claim, and no A-weighted verdict is drawn).

VibrationSoundPowerResult.total_level

property

Band-summed sound power level 10 lg(sum 10^(0.1 L_Wj)), in dB.