aircraft.airport_noise

Noise-Power-Distance (NPD) event-level interpolation (ECAC Doc 29).

The ECAC Doc 29 airport-noise method describes an aircraft’s noise emission with Noise-Power-Distance (NPD) tables: the event noise level (LAmax or the sound exposure level SEL) of an aircraft in steady straight flight on an infinite path, tabulated over a grid of engine power settings and slant distances at reference conditions. Placing an aircraft’s noise at a receiver starts by reading a level from this table for an arbitrary power and distance.

• npd_level — the interpolated event level L(P, d), linear in power and log-linear in distance (Eqs. 4-3/4-4), with extrapolation beyond the tabulated envelope.
• npd_curve — the level over a distance sweep at one power, returned as an NpdLevelResult with a .plot().

The single-event stage segments a flight path and adjusts the NPD baseline per segment (§4.3-4.5): impedance_adjustment (Eq. 4-6/4-7), lateral_attenuation (β, ℓ), engine_installation_correction (φ, mounting), duration_correction, the finite-segment noise_fraction and, behind takeoff ground-roll segments, the start_of_roll_directivity ΔSOR (§4.5.7). event_level assembles and sums them into the SEL/LAmax of a movement (mark takeoff ground-roll segments with the ground_roll mask of its FlightSegmentState), and noise_contour evaluates it over a ground grid.

Source (clean-room, implemented from the standard text): ECAC Doc 29, 4th ed., Vol 2 (2016), §4.2-4.5. Validated per-term and end-to-end against the ECAC Doc 29 5th ed. Vol 3 Part 1 reference workbook.

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

AerodromeAtmosphere

AerodromeAtmosphere(temperature: float = 15.0, pressure: float = 101.325)

The aerodrome air the NPD levels are corrected to (Eq. 4-6/4-7).

The two quantities impedance_adjustment needs, at the standard atmosphere by default, so an event at reference conditions needs no atmosphere at all.

The Doc 32 rotorcraft chain keeps its own RotorcraftAtmosphere instead of sharing this one: it propagates band by band, so it also needs the humidity and the absorption method, and its reference conditions are the ICAO 25 °C/70 % of the hemisphere database, not the 15 °C of Eq. 4-7.

Attributes

Name	Description
temperature	Aerodrome air temperature T, in °C (default 15).
pressure	Aerodrome air pressure p, in kPa (default 101.325).

duration_correction

duration_correction(reference_speed: float, segment_speed: float) -> float

Duration correction (Eq. 4-14, exposure only).

$\Delta V=10\cdot {\log }_{10}(V_{\mathrm{ref}}/V_{\mathrm{seg}})$.

Parameters

Name	Description
reference_speed	NPD reference speed Vref (any consistent unit).
segment_speed	Segment speed Vseg (same unit).

Returns: The duration correction ΔV, in dB.

Raises

Exception	When
ValueError	If a speed is not strictly positive.

engine_installation_correction

engine_installation_correction(
    depression_deg: float,
    mounting: str = 'wing',
) -> float

Engine-installation lateral-directivity correction ΔI(φ) (Eq. 4-15/4-16).

Parameters

Name	Description
depression_deg	Depression angle φ (from the wing plane), in degrees.
mounting	"wing", "fuselage" or "propeller".

Returns: The correction ΔI, in dB (added to the level).

Raises

Exception	When
ValueError	If mounting is unknown or the angle is non-finite.

event_level

event_level(
    path: NDArray[np.float64] | list[list[float]],
    observer: NDArray[np.float64] | list[float],
    powers: NDArray[np.float64] | list[float],
    distances: NDArray[np.float64] | list[float],
    exposure_levels: NDArray[np.float64] | list[list[float]],
    maximum_levels: NDArray[np.float64] | list[list[float]],
    *,
    reference_speed: float = 82.31104,
    mounting: str = 'wing',
    metric: str = 'exposure',
    atmosphere: AerodromeAtmosphere = ...,
    segments: FlightSegmentState = ...,
) -> FlyoverResult

Single-event noise level of a flight path at a receiver (ECAC Doc 29).

Assembles the segment event levels (Eq. 4-8/4-9), the NPD baseline plus the duration, engine-installation, lateral-attenuation and finite-segment (noise-fraction) corrections, and the start-of-roll directivity behind takeoff ground-roll segments, and combines them into the exposure level SEL (energy sum, Eq. 4-11) or the maximum level (Eq. 4-10).

Parameters

Name	Description
path	Flight-path points, shape (N, 5): columns x, y, z (m), engine power setting and speed (m/s). N-1 segments are formed.
observer	Receiver position (x, y, z), in metres.
powers	NPD tabulated power settings.
distances	NPD tabulated slant distances, in metres.
exposure_levels	NPD exposure (SEL) levels, shape (P, D).
maximum_levels	NPD maximum levels, shape (P, D).
reference_speed	NPD reference speed, in m/s (default 160 kn).
mounting	Engine mounting ("wing"/"fuselage"/"propeller").
metric	"exposure" (SEL) or "maximum" (LAmax).
atmosphere	Aerodrome air temperature and pressure, an AerodromeAtmosphere (default: the standard atmosphere); they set the impedance adjustment.
segments	What each segment is doing, a FlightSegmentState (default: airborne and unbanked): the takeoff ground-roll and landing-rollout masks and the per-segment bank angle.

Returns: A FlyoverResult. If every segment is degenerate (zero length) the level is -inf.

Raises

Exception	When
ValueError	If the inputs are invalid.

FlightSegmentState

FlightSegmentState(
    ground_roll: NDArray[np.bool_] | list[bool] | None = None,
    landing_roll: NDArray[np.bool_] | list[bool] | None = None,
    bank: NDArray[np.float64] | list[float] | None = None,
)

What each segment of a flight path is doing (§4.5.2/4.5.5-4.5.7).

One entry per segment, so every field an N-point path fills has length N-1. Everything left unset describes an airborne, unbanked movement.

Attributes

Name	Description
ground_roll	Optional boolean mask marking takeoff ground-roll segments; these receive the start-of-roll directivity ΔSOR and reduced noise fraction behind the aircraft (§4.5.6-4.5.7).
landing_roll	Optional boolean mask marking landing rollout segments; ahead of them the reduced fraction (Eq. 4-21b), the nearest-end lateral geometry and no directivity term apply (§4.5.5-4.5.6).
bank	Optional per-segment bank angle ε in degrees, measured counter-clockwise about the roll axis (positive in a left turn, starboard wing up); the depression angle becomes $\varphi =\beta +\epsilon$ for observers to starboard (right) of the track and $\varphi =\beta -\epsilon$ for observers to port (§4.5.2).

FlyoverResult

FlyoverResult(
    level: float,
    metric: str,
    segment_levels: NDArray[np.float64],
    observer: NDArray[np.float64],
)

Single-event noise level of an aircraft movement at a receiver.

Attributes

Name	Description
level	The event level, in dB (SEL for metric="exposure", else the maximum level).
metric	"exposure" (SEL) or "maximum" (LAmax).
segment_levels	Per-segment contribution, in dB.
observer	Receiver position (x, y, z), in metres.

FlyoverResult.plot()

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

Plot the per-segment contributions to the event level.

impedance_adjustment

impedance_adjustment(
    temperature: float = 15.0,
    pressure: float = 101.325,
) -> float

Acoustic-impedance adjustment of the standard NPD data (Eq. 4-6/4-7).

The ANP NPD levels are normalised to a reference specific acoustic impedance of 409.81 N·s/m³. At the aerodrome’s temperature and pressure the air impedance is $\rho c=416.86\cdot (\delta /\sqrt{\theta })$ with $\delta =p/p_0$ and $\theta =(T+273.15)/(T_0+273.15)$, and the adjustment $10\cdot {\log }_{10}(\rho c/409.81)$ is added to the NPD levels. Under the standard atmosphere it is +0.074 dB.

Parameters

Name	Description
temperature	Aerodrome air temperature T, in °C (default 15 °C).
pressure	Aerodrome air pressure p, in kPa (default 101.325 kPa).

Returns: The impedance adjustment, in dB (added to the NPD level).

Raises

Exception	When
ValueError	If the pressure is not positive or inputs are non-finite.

lateral_attenuation

lateral_attenuation(elevation_deg: float, lateral_m: float) -> float

Excess lateral attenuation Λ(β, ℓ) over soft ground (Eq. 4-18/4-19).

Parameters

Name	Description
elevation_deg	Elevation angle β of the (equivalent level) path, in degrees.
lateral_m	Lateral displacement ℓ from the ground track, in metres.

Returns: The lateral attenuation Λ, in dB (subtracted from the level).

Raises

Exception	When
ValueError	If lateral_m is negative or non-finite.

noise_contour

noise_contour(
    path: NDArray[np.float64] | list[list[float]],
    powers: NDArray[np.float64] | list[float],
    distances: NDArray[np.float64] | list[float],
    exposure_levels: NDArray[np.float64] | list[list[float]],
    maximum_levels: NDArray[np.float64] | list[list[float]],
    *,
    x: NDArray[np.float64] | list[float],
    y: NDArray[np.float64] | list[float],
    reference_speed: float = 82.31104,
    mounting: str = 'wing',
    metric: str = 'exposure',
    atmosphere: AerodromeAtmosphere = ...,
    segments: FlightSegmentState = ...,
) -> NoiseContourResult

Single-event noise level over a ground grid (ECAC Doc 29 contour).

Evaluates event_level at every grid point (xi, yj, 0).

Parameters

Name	Description
path	Flight-path points, shape (N, 5) (see event_level).
powers	NPD tabulated power settings.
distances	NPD tabulated slant distances, in metres.
exposure_levels	NPD exposure (SEL) levels, shape (P, D).
maximum_levels	NPD maximum levels, shape (P, D).
x	Grid x coordinates, in metres.
y	Grid y coordinates, in metres.
reference_speed	NPD reference speed, in m/s.
mounting	Engine mounting.
metric	"exposure" (SEL) or "maximum" (LAmax).
atmosphere	Aerodrome air temperature and pressure, an AerodromeAtmosphere (impedance adjustment).
segments	What each segment is doing, a FlightSegmentState (see event_level).

Returns: A NoiseContourResult.

Raises

Exception	When
ValueError	If the inputs are invalid.

noise_fraction

noise_fraction(
    q: float,
    segment_length: float,
    scaled_distance: float,
) -> float

Finite-segment correction (noise fraction) ΔF (Eq. 4-20, exposure only).

Parameters

Name	Description
q	Signed distance from the segment start S1 to the perpendicular foot Sp, in metres (negative behind the segment).
segment_length	Segment length λ, in metres (> 0).
scaled_distance	The scaled distance dλ (Appendix E), in metres (> 0).

Returns: The finite-segment correction ΔF, in dB (<= 0, floored at −150 dB).

Raises

Exception	When
ValueError	If segment_length or scaled_distance is not positive.

NoiseContourResult

NoiseContourResult(
    x: NDArray[np.float64],
    y: NDArray[np.float64],
    level: NDArray[np.float64],
    metric: str,
)

Single-event noise level over a ground grid (ECAC Doc 29).

Attributes

Name	Description
x	Grid x coordinates, in metres.
y	Grid y coordinates, in metres.
level	Event level over the grid (len(y), len(x)), in dB.
metric	"exposure" (SEL) or "maximum" (LAmax).

NoiseContourResult.plot()

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

Plot filled noise contours over the ground plane.

npd_curve

npd_curve(
    powers: NDArray[np.float64] | list[float],
    distances: NDArray[np.float64] | list[float],
    levels: NDArray[np.float64] | list[list[float]],
    power: float,
    query_distances: NDArray[np.float64] | list[float] | None = None,
) -> NpdLevelResult

NPD event level over a distance sweep at one power setting.

Parameters

Name	Description
powers	Tabulated engine power settings.
distances	Tabulated slant distances, in metres.
levels	Tabulated event levels, shape (len(powers), len(distances)).
power	Query engine power setting.
query_distances	Distances to evaluate, in metres; defaults to a log sweep across the tabulated envelope.

Returns: An NpdLevelResult.

Raises

Exception	When
ValueError	If the inputs are invalid.

npd_level

npd_level(
    powers: NDArray[np.float64] | list[float],
    distances: NDArray[np.float64] | list[float],
    levels: NDArray[np.float64] | list[list[float]],
    power: float,
    distance: NDArray[np.float64] | list[float] | float,
) -> NDArray[np.float64]

Interpolated NPD event level L(P, d) (ECAC Doc 29 §4.2, Eqs. 4-3/4-4).

Interpolates log-linearly in slant distance (Eq. 4-4) at the two bracketing tabulated powers, then linearly in power (Eq. 4-3). Queries outside the tabulated envelope are extrapolated from the terminal segments.

Parameters

Name	Description
powers	Tabulated engine power settings (1-D, strictly increasing).
distances	Tabulated slant distances, in metres (1-D, strictly increasing, positive).
levels	Tabulated event levels, shape (len(powers), len(distances)), in dB.
power	Query engine power setting P.
distance	Query slant distance(s) d, in metres.

Returns: The interpolated event level per query distance, in dB.

Raises

Exception	When
ValueError	If the table or inputs are invalid.

NpdLevelResult

NpdLevelResult(
    distance: NDArray[np.float64],
    level: NDArray[np.float64],
    power: float,
    table_distances: NDArray[np.float64],
    table_levels: NDArray[np.float64],
)

NPD event level over a distance sweep at one power (ECAC Doc 29).

Attributes

Name	Description
distance	Slant distances, in metres.
level	Interpolated event level per distance, in dB.
power	The engine power setting queried.
table_distances	The tabulated slant distances, in metres.
table_levels	The tabulated levels at the queried power, in dB.

NpdLevelResult.plot()

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

Plot the interpolated level versus slant distance (log axis).

start_of_roll_directivity

start_of_roll_directivity(
    azimuth_deg: float,
    distance_m: float,
    engine: str = 'jet',
) -> float

Start-of-roll (ground-roll) directivity correction ΔSOR (Eq. 4-22/4-25).

Behind a takeoff ground-roll segment, jet-exhaust noise radiates a lobed rearward pattern. ΔSOR adjusts the segment level relative to the level to the side of the start of roll, as a function of the azimuth ψ between the aircraft forward axis and the observer (Eq. 4-24a for turbofan jets, 4-24b for turboprops), scaled beyond 762 m by $d_{SOR,0}/d_{SOR}$ (Eq. 4-25). It is only applied behind takeoff ground-roll segments ($90^{\circ }\le \psi \le 180^{\circ }$); ahead of the aircraft ($\psi <90^{\circ }$) it is zero.

Parameters

Name	Description
azimuth_deg	Azimuth ψ from the forward axis to the observer, in degrees ($\psi =\arccos (q/d_{SOR})$, in [90, 180] behind the aircraft). Values below 90° return 0; values above 180° are clamped to 180°.
distance_m	Distance dSOR from the observer to the segment start, in metres.
engine	"jet" (turbofan, Eq. 4-24a) or "turboprop" (Eq. 4-24b).

Returns: The directivity correction ΔSOR, in dB (added to the level).

Raises

Exception	When
ValueError	If engine is unknown or the inputs are invalid.