emission.sound_power_intensity

Sound power level of a noise source by sound-intensity scanning: ISO 9614-2:1996 (engineering, grade 2; survey/control, grade 3).

A probe is swept continuously over each segment of a hypothetical surface that encloses the source, reporting the time-averaged signed normal intensity <In,i> and mean-square pressure per segment. The sound power follows from the partial powers Pi = <In,i>*Si summed over the N segments (clause 9, equations (5), (6), (12), (13)):

Pi = <In,i> * Si                       (partial power, Eq. 12)
P  = sum_i Pi                          (total power, Eq. 6)
LW = 10*lg(P/P0),  P0 = 1e-12 W        (sound power level, Eq. 13)

The method is not applicable to any band in which P < 0 (clause 9.2): a strong parasitic source outside the surface makes the net energy flow inward and the determination invalid for that band.

Two scanning-method field indicators qualify the determination (Annex A, normative):

FpI  = [Lp] - LW + 10*lg(S/S0)                       (Eq. A.1)
[Lp] = 10*lg( (1/S) * sum_i Si*10^(0,1*Lpi) )        (area-weighted surface SPL)
F+/- = 10*lg( sum_i |Pi| / |sum_i Pi| )              (Eq. A.2)

FpI is the surface pressure-intensity indicator (equivalent to ISO 9614-1 F3 for uniform-area segments, Note 14); F+/- the negative-partial-power indicator (equivalent to ISO 9614-1 F3-F2, Note 15). Because Part 2 weights by segment area Si while phonometry.field_indicators (ISO 9614-1) assumes equal-area positions, the indicators are computed directly here; only the dynamic-capability index Ld = delta_pI0 - K is shared with phonometry.dynamic_capability_index.

Qualification criteria per band (Annex B):

criterion 1:  Ld > FpI        Ld = delta_pI0 - K  (K = 10 eng / 7 survey, Table 1)
criterion 2:  F+/- <= 3 dB    (mandatory grade 2; optional grade 3)
criterion 3:  |LWi(1) - LWi(2)| <= s   per segment  (s from Table 2)

A band achieves the engineering grade when criteria 1, 2 and 3 hold, the survey grade when criteria 1 and 3 hold (clause 8.4), otherwise none. An A-weighted sound power level omits, besides the non-determinable P <= 0 bands, the bands in which criteria 1 and/or 2 are not satisfied (clause 10.6 b).

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sound_power_intensity

sound_power_intensity(
    normal_intensity: np.ndarray,
    areas: np.ndarray,
    *,
    normal_intensity_2: np.ndarray | None = None,
    pressure_levels: np.ndarray | None = None,
    pressure_residual_index: float | np.ndarray | None = None,
    frequencies: np.ndarray | None = None,
    band_type: BandType = 'third',
    grade: Grade = 'engineering',
    repeatability_limit: float | np.ndarray | None = None,
) -> SoundPowerIntensityResult

Sound power level by sound-intensity scanning (ISO 9614-2:1996).

normal_intensity is an (N_seg, N_bands) array (or (N_seg,) for a single band) of the signed, segment-averaged normal sound intensity <In,i> (W/m^2), and areas the (N_seg,) segment areas Si (m^2). The partial powers Pi = <In,i>*Si are summed to the band sound power P and level LW = 10*lg(P/P0) (equations (12), (6), (13)). Bands with P < 0 are flagged (negative_band) and reported as NaN (clause 9.2).

Supplying normal_intensity_2 (the second grade-2 sweep) makes normal_intensity the first sweep, uses their mean for the partial powers (Eq. 12), and evaluates the repeatability criterion 3. Supplying pressure_levels (Lpi) evaluates FpI (Eq. A.1) and, with pressure_residual_index (delta_pI0), criterion 1. The per-band achieved grade (clause 8.4) is returned when both a second sweep and delta_pI0 are available. When criteria 1 and 2 are evaluable (pressure_levels and pressure_residual_index supplied), the bands failing them are omitted from the A-weighted total and flagged in a_weighting_omitted_bands (clause 10.6 b); otherwise every determinable band is summed and a SoundPowerWarning notes the missing screening.

Parameters

Name	Description
normal_intensity	(N_seg, N_bands) signed normal intensity, W/m^2.
areas	(N_seg,) segment areas Si, m^2.
normal_intensity_2	Optional second sweep, same shape (criterion 3).
pressure_levels	Optional (N_seg, N_bands) Lpi (dB) for FpI.
pressure_residual_index	delta_pI0 (dB), scalar or per band, for the dynamic-capability index / criterion 1.
frequencies	(N_bands,) nominal band centres (Hz), for the A-weighted total and the Table 2 repeatability limits.
band_type	'octave' or 'third' (Table 2 lookup).
grade	'engineering' (grade 2) or 'survey' (grade 3); selects K for the reported Ld and the criterion-2 warning.
repeatability_limit	Override for the criterion-3 limit s (dB), scalar or per band; defaults to ISO 9614-2 Table 2 by frequencies for 'engineering'. For 'survey' the default is the A-weighted 4 dB reused per band (extrapolated — non-normative).

Returns: SoundPowerIntensityResult.

SoundPowerIntensityResult

SoundPowerIntensityResult(
    frequencies: np.ndarray | None,
    partial_power: np.ndarray,
    partial_power_level: np.ndarray,
    sound_power: np.ndarray,
    sound_power_level: np.ndarray,
    negative_band: np.ndarray,
    surface_pressure_intensity_index: np.ndarray | None,
    negative_partial_power_index: np.ndarray | None,
    repeatability: np.ndarray | None,
    dynamic_capability_index: np.ndarray | None,
    achieved_grade: np.ndarray | None,
    surface_area: float,
    sound_power_level_a: float,
    a_weighting_omitted_bands: np.ndarray | None,
    grade: str,
)

Result of an ISO 9614-2:1996 sound-power-by-scanning determination.

partial_power is the signed Pi = <In,i>*Si per segment and band (Eq. 12); partial_power_level the magnitude level 10*lg(|Pi|/P0) (Eq. 8), with the sign carried by partial_power. sound_power is the signed band total P = sum Pi (Eq. 6) and sound_power_level its level 10*lg(P/P0) (Eq. 13), NaN where P <= 0 (negative_band True, method not applicable, clause 9.2). surface_pressure_intensity_index (FpI, Eq. A.1) and negative_partial_power_index (F+/-, Eq. A.2) are per band, None when the inputs they need are absent. repeatability is |LWi(1)-LWi(2)| per segment and band (criterion 3), None without a second scan; it is +inf where the two sweeps reverse the flow direction on a segment (opposite-sign partial powers), a gross non-repeatability that criterion 3 must reject even when the magnitudes happen to match. dynamic_capability_index is Ld for the requested grade. achieved_grade is the per-band class 'engineering'/ 'survey'/'none' (clause 8.4), None when the qualifying inputs (delta_pI0 and a second scan) are absent. sound_power_level_a is the A-weighted total over determinable bands (NaN without frequencies and more than one band), which omits the bands failing criteria 1 and/or 2 (clause 10.6 b) whenever those criteria are evaluable. a_weighting_omitted_bands flags the bands so omitted (per band, True = omitted); it is None when the criteria inputs (pressure_levels and pressure_residual_index) are absent, in which case every determinable band is summed and a warning is emitted.

SoundPowerIntensityResult.plot()

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

Plot the LW spectrum; non-positive bands are hatched as unusable.

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

SoundPowerIntensityResult.report()

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

Render an ISO 9614-2 sound-power-by-intensity determination fiche.

Writes a one-page sound-power test sheet: the standard-basis line naming the intensity-scanning method and its measurement grade (ISO 9614-2:1996 engineering grade 2 or survey grade 3), an optional metadata header (client, noise source, test environment, instrumentation, climate, date), a per-band table (nominal octave/one-third-octave frequency and the intensity-derived band sound-power level LW), the sound-power spectrum LW(f) with net-negative bands hatched as unusable, the boxed A-weighted sound power level LWA (dB re 1 pW) with the total LW, the measurement surface area S and the determination grade, an optional verdict row against a declared limit, and a measurement-basis strip stating the partial-power model, the field indicators (FpI, F+/-) and the Annex B qualification criteria.

Parameters

Name	Description
path	Destination path of the PDF file.
metadata	Optional ReportMetadata supplying the header (client, specimen the noise 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).
engine	Rendering back end; only "reportlab" is supported.
verbose	When True the per-band table adds the field indicators FpI and F+/- and the per-band achieved grade.
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]).