environmental.wind_turbine_noise

Wind-turbine acoustic noise (IEC 61400-11:2012+A1:2018).

Two closed-form quantities of the standard:

• apparent_sound_power_level — the A-weighted apparent sound power level L_WA referred to the equivalent point source at the rotor centre, from the ground-board sound pressure level and the slant distance (slant_distance), L_WA = L_p − 6 + 10·lg(4π R1²/S0) (Formula 26).
• wind_turbine_tonality — the tonal-audibility chain (Formulae 30-34): the critical bandwidth (critical_bandwidth), the masking-noise level, the tonality and the audibility criterion, giving the tonal audibility ΔL_a that decides whether a tone is audible.

The tonal-audibility formula itself is the ISO 1996-2 Annex C one already in phonometry.environmental_measurement; what is specific to IEC 61400-11 is how the tone and masking-noise levels and the (Zwicker) critical band are determined from the narrowband spectrum. The rating adjustment K_T is the ISO 1996-2 tonal_adjustment. The full measurement pipeline (binning, regression to standardised wind speeds, uncertainty budgets) is out of scope; these are the underlying closed forms.

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

apparent_sound_power_level

apparent_sound_power_level(
    band_levels: float | NDArray[np.float64] | list[float],
    r1: float,
) -> float

A-weighted apparent sound power level L_WA (IEC 61400-11 Formula 26).

L_WA,i = L_p,i − 6 + 10·lg(4π R1²/S0) per one-third-octave band, energy summed over bands (Formula 27). The −6 dB accounts for the ground-board pressure doubling; S0 = 1 m².

Parameters

Name	Description
band_levels	Background-corrected A-weighted band sound pressure levels L_p,i, in dB (scalar or per band). The 61400-11-specific background correction (Formula 23 subtraction with the 3-6 dB asterisk marking and the <= 3 dB not-reported rule, subclause 9.3) is out of scope here and must be applied beforehand; note its rule set differs from the ISO 1996-2 correction in phonometry.environmental.measurement.residual_sound_correction.
r1	Slant distance R1 to the rotor centre, in m.

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

Raises

Exception	When
ValueError	If the inputs are invalid.

slant_distance

slant_distance(
    hub_height: float,
    rotor_diameter: float,
    *,
    rotor_axis: str = 'horizontal',
) -> float

Slant distance R1 from the rotor centre to the ground microphone.

With the reference microphone on the ground at the horizontal distance R0 and the rotor centre at height H, the slant distance is R1 = sqrt(H² + R0²). For a horizontal-axis turbine R0 = H + D/2 (IEC 61400-11 Formula 1); for a vertical-axis turbine R0 = H + D (Formula 2, with H the height of the equator of the rotor).

Parameters

Name	Description
hub_height	Hub height H (ground to rotor centre; for a vertical-axis turbine, to the rotor equator), in m.
rotor_diameter	Rotor diameter D, in m.
rotor_axis	"horizontal" (Formula 1, the default) or "vertical" (Formula 2).

Returns: The slant distance R1, in m.

Raises

Exception	When
ValueError	If a dimension is not positive or rotor_axis is not one of the two orientations.

wind_turbine_tonality

wind_turbine_tonality(
    levels: NDArray[np.float64] | list[float],
    frequencies: NDArray[np.float64] | list[float],
    *,
    tone_frequency: float | None = None,
) -> WindTurbineTonalityResult

Tonal audibility of a narrowband spectrum (IEC 61400-11 Formulae 30-34).

From a uniformly-spaced narrowband spectrum, screens the candidate as a possible tone (subclause 9.5.2: a local maximum more than 6 dB above the critical-band energy average excluding the maximum and its two adjacent lines), classifies the lines in the critical band about the candidate into masking noise and tone lines, forms the masking-noise level L_pn (Formula 31), the tonality ΔL_tn = L_pt − L_pn (Formula 32), the audibility criterion L_a (Formula 34) and the tonal audibility ΔL_a = ΔL_tn − L_a (Formula 33).

Per subclause 9.5.3 the tone lines are those above L_pn,avg + 6 dB and within 10 dB of the highest such line; the frequency of the tone is that highest line (9.5.4), which also anchors L_a. When the candidate fails the 9.5.2 screening or no line classifies as “tone”, the result carries has_identified_tone = False: its numeric fields are non-standard fallbacks and the spectrum must be excluded from the 9.5.1 bin averaging (see WindTurbineTonalityResult).

Spectra must extend over the whole critical band: a truncated band leaves the masking average over the surviving lines while Formula 31 still scales to the full bandwidth, so a WindTurbineNoiseWarning is issued. Candidates below 20 Hz are outside the standard’s analysis range (the critical band would extend to negative frequencies) and are rejected.

Parameters

Name	Description
levels	Narrowband line levels, in dB (A-weighted, 1-2 Hz resolution).
frequencies	Line frequencies, in Hz (uniform spacing).
tone_frequency	Candidate tone frequency, in Hz; if None the highest-level line is used.

Returns: A WindTurbineTonalityResult.

Raises

Exception	When
ValueError	If the inputs are invalid or the candidate lies below 20 Hz.

WindTurbineNoiseWarning

The tonality inputs leave the standard’s stated domain of validity.

WindTurbineTonalityResult

WindTurbineTonalityResult(
    tone_frequency: float,
    critical_bandwidth: float,
    tone_level: float,
    masking_level: float,
    tonality: float,
    audibility_criterion: float,
    tonal_audibility: float,
    is_audible: bool,
    has_identified_tone: bool,
    frequencies: NDArray[np.float64],
    levels: NDArray[np.float64],
)

Tonal audibility of a narrowband spectrum (IEC 61400-11).

Attributes

Name	Description
tone_frequency	The frequency of the identified tone: the spectral line with the highest level among the lines classified as “tone” (subclause 9.5.4; also the f of Formula 34). When no tone is identified (has_identified_tone is False) this falls back to the candidate line.
critical_bandwidth	The critical bandwidth about the candidate, Hz.
tone_level	Tone level L_pt (energy sum of the tone lines), in dB.
masking_level	Masking-noise level L_pn, in dB.
tonality	Tonality ΔL_tn = L_pt − L_pn, in dB.
audibility_criterion	The criterion L_a (Formula 34), in dB.
tonal_audibility	Tonal audibility ΔL_a = ΔL_tn − L_a, in dB.
is_audible	Whether an identified tone is audible (ΔL_a > 0 and has_identified_tone).
has_identified_tone	Whether the candidate passed the 9.5.2 possible-tone screening and at least one spectral line was classified as “tone” (subclause 9.5.4). When False the numeric fields are non-standard fallbacks (the standard defines no tonality for such a spectrum) and the spectrum must be excluded from the 9.5.1 energy averaging of ΔL_a,j,k over the spectra of a bin.
frequencies	The narrowband line frequencies, in Hz.
levels	The narrowband line levels, in dB.

WindTurbineTonalityResult.plot()

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

Plot the narrowband spectrum with the critical band and masking level.

WindTurbineTonalityResult.report()

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

Render a wind-turbine tonal audibility assessment fiche to a PDF.

Writes a one-page tonality-assessment report following IEC 61400-11:2012+A1:2018 (subclauses 9.5.2 to 9.5.8): the standard-basis line, an optional metadata header (source/situation, client, measurement position, instrumentation and date), a two-panel body with the critical-band / masking analysis in a metrics table (tone frequency, critical bandwidth, tone level L_pt, masking-noise level L_pn, tonality ΔL_tn, audibility criterion L_a and tonal audibility ΔL_a) beside the narrowband-spectrum plot with the critical band, masking level and tone marked, the boxed decisive tonal audibility ΔL_a and the tone frequency with the audibility decision, an optional verdict row and a footer with the fixed disclaimer.

Parameters

Name	Description
path	Destination path of the PDF file.
metadata	Optional ReportMetadata; None produces a bare assessment fiche (body, result and disclaimer only). A supplied requirement is read as the maximum acceptable tonal audibility ΔL_a in dB (a lower audibility passes).
engine	Rendering back end; only "reportlab" is supported.
verbose	Accepted for signature parity with the other fiches; the metrics table already shows the full Formula 30-34 chain, so it has no effect.
language	Fiche language: "en" (default, English) or "es" (Spanish, with a comma decimal separator).

Returns: The written path as a str.

Raises

Exception	When
ValueError	If language is not one of the supported languages, or if engine is not "reportlab".
ImportError	If reportlab is not installed (pip install phonometry[report]).