environment.propagation.outdoor_propagation

Outdoor sound propagation: ISO 9613-2:1996 general method of calculation.

This part of ISO 9613 predicts octave-band attenuation of sound propagating outdoors from a point source to a receiver under conditions favourable to propagation (moderate downwind, or the equivalent moderate temperature inversion; ISO 9613-2:1996, clause 5). The equivalent-continuous downwind octave-band sound pressure level is (ISO 9613-2:1996):

L_{f T} (D W) = L_{W} + D_{c} - A (Eq. 3)

with $L_{W}$ the octave-band sound power level, $D_{c}$ the directivity correction (directivity index plus a solid-angle index DOmega) and A the octave-band attenuation, itself a sum of physical mechanisms:

A = A_{div} + A_{atm} + A_{gr} + A_{bar} + A_{misc} (Eq. 4)

Implemented here are the four general terms of clause 7:

Adiv geometrical divergence, $20 lo g_{10} (d / d_{0}) + 11$ (Eq. (7));
Aatm atmospheric absorption, $α d$ (Eq. (8)) with alpha the ISO 9613-1 coefficient supplied by air_absorption;
Agr ground effect, both the general per-region method of 7.3.1 with the Table 3 functions a'/b'/c'/d' (Eq. (9)) and the alternative simplified method of 7.3.2 (Eq. (10));
Abar screening by a barrier, $D_{z} - A_{gr}$ with the Dz diffraction formula of Eq. (14) including the C2/C3 factors, the pathlength difference z (Eq. (16)/(17)), the meteorological factor Kmet (Eq. (18)) and the 20 dB (single) / 25 dB (double) limits.

The long-term average level follows from the meteorological correction Cmet (Eq. (6), (21), (22), clause 8). Amisc (foliage, industrial sites, housing; annex A) and reflections from vertical obstacles (clause 7.5) are informative and left to the caller. Accuracy of the method is stated in Table 5 (clause 9): within +/-1 dB to +/-3 dB for broadband noise up to 1000 m.

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

atmospheric_absorption

atmospheric_absorption(
    distance: float,
    frequencies: ArrayLike = (63.0, 125.0, 250.0, 500.0, 1000.0, 2000.0, 4000.0, 8000.0),
    temperature: float = 20.0,
    relative_humidity: float | None = None,
    pressure: float = 101.325,
) -> NDArray[np.float64]

Attenuation due to atmospheric absorption (ISO 9613-2:1996, Eq. (8)).

$A_{atm} = α d$ with alpha the ISO 9613-1 atmospheric attenuation coefficient (here in dB/m, from air_attenuation) at each octave-band midband frequency. Eq. (8) writes alpha in dB/km with $A_{atm} = α_{dB/km} d /1000$ ; the two forms are identical.

alpha is evaluated at the exact base-10 midband frequency behind each nominal band label (e.g. 7 943.3 Hz for the “8 kHz” band), the convention behind the ISO 9613-2 Table 2 coefficients (they come from ISO 9613-1 Table 1 at exact midbands; at 8 kHz the nominal-frequency evaluation would run ~1.3 % high). Each supplied frequency is snapped to the nearest exact midband.

Parameters

Name	Description
`distance`	Source-to-receiver distance `d`, in metres.
`frequencies`	Octave-band midband frequencies, in hertz.
`temperature`	Air temperature, in degrees Celsius.
`relative_humidity`	Relative humidity, in percent (default 70).
`pressure`	Atmospheric pressure, in kilopascals.

Returns: Aatm per band, in decibels.

AtmosphericConditions

AtmosphericConditions(
    temperature: float = 20.0,
    relative_humidity: float | None = None,
    pressure: float = 101.325,
)

State of the air behind the atmospheric absorption term Aatm.

The three quantities the ISO 9613-1 attenuation coefficient alpha is a function of (ISO 9613-2:1996, Eq. (8) and Table 2). The defaults are the reference conditions of the tabulated coefficients.

Parameters

Name	Description
`temperature`	Air temperature, in degrees Celsius.
`relative_humidity`	Relative humidity, in percent; `None` uses 70.
`pressure`	Atmospheric pressure, in kilopascals.

Barrier

Barrier(
    source_to_edge: float,
    edge_to_receiver: float,
    parallel_distance: float = 0.0,
    edge_separation: float | None = None,
    ground_reflections_by_image: bool = False,
    lateral: bool = False,
    line_of_sight_clear: bool = False,
)

Screening obstacle for the ISO 9613-2 barrier term (clause 7.4).

The barrier is described by the diffraction geometry that feeds the pathlength-difference equations (16)/(17) directly, which is the cleanest match to the Dz formula of Eq. (14).

Parameters

Name	Description
`source_to_edge`	Distance `dss` from the source to the (first) diffraction edge, in metres (ISO 9613-2:1996, Eq. (16)).
`edge_to_receiver`	Distance `dsr` from the (second) diffraction edge to the receiver, in metres.
`parallel_distance`	Component `a` of the source-receiver separation parallel to the barrier edge, in metres (0 for a purely 2-D section).
`edge_separation`	Spacing `e` between the two diffraction edges for double (thick-barrier) diffraction, in metres; `None` selects single diffraction (Eq. (16), $C_{3} = 1$ ). When given, Eq. (17) and the `C3` factor of Eq. (15) are used with the 25 dB limit.
`ground_reflections_by_image`	When `True` the ground reflections are assumed to be handled separately by image sources, so $C_{2} = 40$ ; otherwise $C_{2} = 20$ (Eq. (14)).
`lateral`	When `True` the diffraction is around a vertical edge (Eq. (13)): $A_{bar} = D_{z}$ (the ground term is not cancelled) and $K_{met} = 1$ . Default `False` selects top-edge diffraction (Eq. (12)).
`line_of_sight_clear`	When `True` the line of sight between source and receiver passes above the top edge: ISO 9613-2:1996 (text after Eq. (16)) then gives the path difference `z` a negative sign, and Eq. (14) is still evaluated (with $K_{met} = 1$ , Eq. (18)), so `Dz` falls continuously from $10 lo g_{10} 3 = 4.8$ dB at grazing to 0 for deeper geometries. The edge distances stay the unsigned geometric lengths; only the sign convention of `z` changes.

Barrier.is_double

property

Whether double diffraction (Eq. (17)/(15)) applies (e given).

barrier_attenuation

barrier_attenuation(
    barrier: Barrier,
    distance: float,
    frequencies: ArrayLike = (63.0, 125.0, 250.0, 500.0, 1000.0, 2000.0, 4000.0, 8000.0),
) -> NDArray[np.float64]

Barrier diffraction attenuation Dz (ISO 9613-2:1996, Eq. (14)).

D_{z} = 10 lo g_{10} [3 + \frac{C _{2}}{λ} C_{3} z K_{met}] dB

with $C_{2} = 20$ (or 40 when ground reflections are handled by image sources), $C_{3} = 1$ for single diffraction or Eq. (15) for double, the pathlength difference z (Eq. (16)/(17)), $λ = 340/ f$ and the meteorological factor Kmet (Eq. (18), 1 for $z \leq 0$ ). Dz is limited to 20 dB (single) or 25 dB (double). When the line of sight passes above the top edge (Barrier(line_of_sight_clear=True)) z takes a negative sign (ISO 9613-2:1996, text after Eq. (16)) and Eq. (14) still applies: Dz falls continuously from $10 lo g_{10} 3 = 4.8$ dB at grazing ( $z = 0$ ) towards 0 as the clearance deepens, clamped at 0 (the logarithm’s argument is floored at 1 — a barrier below the sight line never amplifies).

Parameters

Name	Description
`barrier`	Barrier geometry (`Barrier`).
`distance`	Straight-line source-to-receiver distance `d`, in metres.
`frequencies`	Octave-band midband frequencies, in hertz.

Returns: Dz per band, in decibels (>= 0).

Raises

Exception	When
ValueError	If `distance` or any frequency is not positive.

DEFAULT_FREQUENCIES

Constant (tuple).

DEFAULT_FREQUENCIES = (63.0, 125.0, 250.0, 500.0, 1000.0, 2000.0, 4000.0, 8000.0)

directivity_omega

directivity_omega(
    source_height: float,
    receiver_height: float,
    projected_distance: float,
) -> float

Solid-angle directivity index DOmega (ISO 9613-2:1996, Eq. (11)).

Accounts for the apparent increase in source power from ground reflection near the source when the alternative ground method (Eq. (10)) is used:

D_{Ω} = 10 lo g_{10} {1 + \frac{d _{p}^{2} + ( h _{s} - h _{r} ) ^{2}}{d _{p}^{2} + ( h _{s} + h _{r} ) ^{2}}} dB

Parameters

Name	Description
`source_height`	Source height `hs`, in metres.
`receiver_height`	Receiver height `hr`, in metres.
`projected_distance`	Ground-plane projected distance `dp`, in metres.

Returns: DOmega, in decibels (0 to ~3 dB).

DirectivityCorrection

DirectivityCorrection(index: float = 0.0, d_omega: float = 0.0)

Directivity correction $D_{c} = D_{i} + D_{Ω}$ (Eq. (3)).

The two terms the standard adds to the sound power level of a point source: the directivity index of the source itself and the solid-angle index of the space it radiates into. Both are zero for an omnidirectional source radiating into free space.

Parameters

Name	Description
`index`	Source directivity index `Di`, in decibels.
`d_omega`	Solid-angle index `DOmega`, in decibels (see `directivity_omega` for the alternative ground method).

geometric_divergence

geometric_divergence(distance: float) -> float

Attenuation due to geometrical divergence (ISO 9613-2:1996, Eq. (7)).

Spherical spreading in the free field from a point source:

A_{div} = 20 lo g_{10} (d / d_{0}) + 11 dB, d_{0} = 1 m

The +11 ( $= 10 lo g_{10} 4 π$ ) sets the sound pressure level at the reference distance $d_{0} = 1$ m from an omnidirectional point source (Note 7).

Parameters

Name	Description
`distance`	Straight-line source-to-receiver distance `d`, in metres.

Returns: Adiv, in decibels (51 dB at 100 m, 11 dB at 1 m).

Raises

Exception	When
ValueError	If `distance` is not positive.

ground_attenuation

ground_attenuation(
    distance: float,
    source_height: float,
    receiver_height: float,
    frequencies: ArrayLike = (63.0, 125.0, 250.0, 500.0, 1000.0, 2000.0, 4000.0, 8000.0),
    ground_source: float = 0.0,
    ground_middle: float = 0.0,
    ground_receiver: float = 0.0,
    projected_distance: float | None = None,
) -> NDArray[np.float64]

Ground attenuation by the general per-region method (7.3.1, Eq. (9)).

$A_{gr} = A_{s} + A_{r} + A_{m}$ (source, receiver and middle regions), each evaluated with the Table 3 expressions and its ground factor G (0 = hard, 1 = porous, in between = porous fraction). For the source region $G = G_{s}$ and $h = h_{s}$ ; for the receiver region $G = G_{r}$ and $h = h_{r}$ (Table 3, note 1). The middle-region term uses the overlap factor q of note 2:

q = 0 if d_{p} \leq 30 (h_{s} + h_{r})

q = 1 - \frac{30 ( h _{s} + h _{r} )}{d _{p}} if d_{p} > 30 (h_{s} + h_{r})

with $A_{m} = - 3 q$ at 63 Hz and $A_{m} = - 3 q (1 - G_{m})$ above.

Parameters

Name	Description
`distance`	Straight-line source-to-receiver distance `d`, in metres.
`source_height`	Source height `hs` above ground, in metres.
`receiver_height`	Receiver height `hr` above ground, in metres.
`frequencies`	Octave-band midband frequencies, in hertz. Table 3 is defined for the eight nominal octave bands 63 Hz-8 kHz only; any other requested frequency is snapped to the nearest nominal octave band for the Table 3 lookup.
`ground_source`	Ground factor `Gs` of the source region ([0, 1]).
`ground_middle`	Ground factor `Gm` of the middle region ([0, 1]).
`ground_receiver`	Ground factor `Gr` of the receiver region ([0, 1]).
`projected_distance`	Ground-plane projected distance `dp`, in metres; defaults to $d^{2} - (h_{s} - h_{r})^{2}$ .

Returns: Agr per band, in decibels (negative denotes a net gain).

Raises

Exception	When
ValueError	If a ground factor is outside `[0, 1]`, `distance` is not positive, a height is negative, or a frequency is not positive.

ground_attenuation_alternative

ground_attenuation_alternative(distance: float, mean_height: float) -> float

Ground attenuation by the alternative A-weighted method (7.3.2, Eq. (10)).

Valid only when the A-weighted receiver level alone is of interest, the sound propagates over porous or mostly-porous ground and is not a pure tone (ISO 9613-2:1996, 7.3.2):

A_{gr} = 4.8 - \frac{2 h _{m}}{d} [17 + \frac{300}{d}] \geq 0 dB

Negative results are replaced by zero. When this method is used, add the solid-angle index directivity_omega (Eq. (11)) to Dc in Eq. (3).

Parameters

Name	Description
`distance`	Source-to-receiver distance `d`, in metres.
`mean_height`	Mean height `hm` of the propagation path above the ground ( $h_{m} = F / d$ , figure 3), in metres.

Returns: Agr, in decibels (>= 0).

Raises

Exception	When
ValueError	If `distance` is not positive.

GroundFactors

GroundFactors(
    source: float = 0.0,
    middle: float = 0.0,
    receiver: float = 0.0,
)

Ground factors G of the three regions (ISO 9613-2:1996, clause 7.3.1).

The general ground method splits the path into a source region, a middle region and a receiver region, each with its own factor between 0 (hard ground: paving, water, ice, compacted ground) and 1 (porous ground: grass, trees, farmland). The default is hard ground throughout.

Parameters

Name	Description
`source`	Ground factor `Gs` of the source region ([0, 1]).
`middle`	Ground factor `Gm` of the middle region ([0, 1]).
`receiver`	Ground factor `Gr` of the receiver region ([0, 1]).

mean_path_height

mean_path_height(
    profile_distances: ArrayLike,
    profile_heights: ArrayLike,
    source_height: float,
    receiver_height: float,
    distance: float | None = None,
) -> float

Mean height hm of the propagation path above the ground (Figure 3).

The alternative ground method of ISO 9613-2:1996, 7.3.2 is written in one quantity the standard defines by a drawing: $h_{m} = F / d$ , with F the area between the straight source-to-receiver ray and the ground beneath it (Figure 3). This computes that area for a ground given as a polyline, which is the shape a terrain model reduces to once it is cut along the vertical plane through source and receiver.

Source and receiver stand on the two ends of the profile, so the ray runs from $g (0) + h_{s}$ to $g (d_{p}) + h_{r}$ and the profile fixes both the ground-projected length and the height difference the slant distance is built from.

Parameters

Name	Description
`profile_distances`	Ground-projected distance of each profile point from the source, in metres, strictly increasing.
`profile_heights`	Ground height at each profile point, in metres, on any one datum (only differences are used).
`source_height`	Source height `hs` above the ground at the first profile point, in metres.
`receiver_height`	Receiver height `hr` above the ground at the last profile point, in metres.
`distance`	Source-to-receiver distance `d` to divide the area by, in metres; `None` takes the slant distance the profile implies.

Returns: hm, in metres.

Raises

Exception	When
ValueError	If the two sequences disagree in length, describe fewer than two points, the distances are not strictly increasing, `source_height` or `receiver_height` is negative or not finite, or `distance` is not positive and finite. The profile heights themselves are unrestricted: they are read on any datum, so a ground below it is a negative number rather than a mistake.

meteorological_correction

meteorological_correction(
    projected_distance: float,
    source_height: float,
    receiver_height: float,
    c0: float,
) -> float

Meteorological correction Cmet (ISO 9613-2:1996, Eq. (21)/(22)).

C_{met} = 0 if d_{p} \leq 10 (h_{s} + h_{r})

C_{met} = C_{0} [1 - \frac{10 ( h _{s} + h _{r} )}{d _{p}}] if d_{p} > 10 (h_{s} + h_{r})

C0 (dB) reflects local wind and temperature-gradient statistics; practical values lie in 0..~5 dB (note 22). Subtract Cmet from LAT(DW) for the long-term average level (Eq. (6)).

Parameters

Name	Description
`projected_distance`	Ground-plane projected distance `dp`, in metres.
`source_height`	Source height `hs`, in metres.
`receiver_height`	Receiver height `hr`, in metres.
`c0`	Meteorological factor `C0`, in decibels.

Returns: Cmet, in decibels (>= 0 for $C_{0} \geq 0$ ).

outdoor_propagation_attenuation

outdoor_propagation_attenuation(
    distance: float,
    source_height: float,
    receiver_height: float,
    frequencies: ArrayLike = (63.0, 125.0, 250.0, 500.0, 1000.0, 2000.0, 4000.0, 8000.0),
    ground_source: float = 0.0,
    ground_middle: float = 0.0,
    ground_receiver: float = 0.0,
    barrier: Barrier | None = None,
    temperature: float = 20.0,
    relative_humidity: float | None = None,
    pressure: float = 101.325,
    projected_distance: float | None = None,
) -> OutdoorAttenuation

Total octave-band outdoor attenuation (ISO 9613-2:1996, Eq. (4)).

Assembles the four general terms of clause 7 into $A = A_{div} + A_{atm} + A_{gr} + A_{bar}$ (the informative Amisc is omitted). The ground effect uses the general per-region method (7.3.1). With a barrier, the top-edge insertion loss $A_{bar} = D_{z} - A_{gr}$ (Eq. (12)) folds the ground effect of the screened path into Dz (note 13); for a lateral (vertical-edge) barrier $A_{bar} = D_{z}$ (Eq. (13)) and the ground term is retained.

Parameters

Name	Description
`distance`	Straight-line source-to-receiver distance `d`, in metres.
`source_height`	Source height `hs` above ground, in metres.
`receiver_height`	Receiver height `hr` above ground, in metres.
`frequencies`	Octave-band midband frequencies, in hertz. The ground term snaps each frequency to the nearest nominal octave band (Table 3 is octave-band only) and the atmospheric term evaluates the exact base-10 midband behind it (see `atmospheric_absorption`).
`ground_source`	Ground factor `Gs` of the source region ([0, 1], 0 = hard, 1 = porous).
`ground_middle`	Ground factor `Gm` of the middle region ([0, 1]).
`ground_receiver`	Ground factor `Gr` of the receiver region ([0, 1]).
`barrier`	Optional screening obstacle (`Barrier`).
`temperature`	Air temperature, in degrees Celsius.
`relative_humidity`	Relative humidity, in percent (default 70).
`pressure`	Atmospheric pressure, in kilopascals.
`projected_distance`	Ground-plane projected distance `dp`, in metres; defaults to $d^{2} - (h_{s} - h_{r})^{2}$ .

Returns: OutdoorAttenuation with the per-band term breakdown.

Raises

Exception	When
ValueError	If `distance` is not positive.

OutdoorAttenuation

OutdoorAttenuation(
    frequencies: NDArray[np.float64],
    a_div: NDArray[np.float64],
    a_atm: NDArray[np.float64],
    a_gr: NDArray[np.float64],
    a_bar: NDArray[np.float64],
    a_total: NDArray[np.float64],
    d_omega: NDArray[np.float64],
)

Per-octave-band ISO 9613-2 attenuation breakdown (clause 7).

Every array is aligned with frequencies. The terms sum, band by band, to a_total (ISO 9613-2:1996, Eq. (4) without the informative Amisc), so users can see the divergence, atmospheric, ground and barrier contributions separately.

Attributes

Name	Description
`frequencies`	Nominal octave-band midband frequencies, in hertz.
`a_div`	Geometrical divergence `Adiv` (Eq. (7)), in dB, per band (identical across bands).
`a_atm`	Atmospheric absorption `Aatm` (Eq. (8)), in dB, per band.
`a_gr`	Ground effect `Agr` (Eq. (9) or (10)), in dB, per band. A negative value denotes a net gain from ground reflection.
`a_bar`	Screening `Abar` (Eq. (12)/(13)), in dB, per band (>= 0).
`a_total`	Total attenuation `A` (Eq. (4)), in dB, per band.
`d_omega`	Solid-angle directivity index `DOmega` (Eq. (11)), in dB; non-zero only for the alternative ground method of 7.3.2.

OutdoorAttenuation.plot()

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

Plot the stacked per-band attenuation terms with the total.

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

OutdoorAttenuation.report()

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

Render a one-page ISO 9613-2 outdoor-propagation prediction fiche.

Writes a prediction sheet (clearly labelled a prediction, not a measurement) laid out like an environmental-noise propagation calculation: the standard-basis line naming ISO 9613-2:1996 (general method, conditions favourable to propagation), an optional metadata header (source/situation, client, receiver position, meteorological conditions, date), a per-band table of the attenuation terms (Adiv, Aatm, Agr, Abar and the total A) and the attenuation-breakdown plot, closed by a boxed single result and a footer identity/disclaimer block.

When a source_emission is supplied, the fiche also lists the source power level Lw and the composed downwind level LfT(DW) per band and boxes the A-weighted downwind level LAT(DW) at the receiver, with an optional PASS/FAIL verdict against a declared limit level (a lower level is better). Without it the fiche boxes the octave-band range of the total attenuation A.

Parameters

Name	Description
`path`	Destination path of the PDF file.
`metadata`	Optional `ReportMetadata` supplying the header identity (`specimen` the source/situation, `client`, `test_room` the receiver position), the `temperature` / `relative_humidity` / `pressure` conditions and the footer identity. A supplied `requirement` is read as the maximum acceptable A-weighted downwind level in dB (used only when a `source_emission` is given).
`engine`	Rendering back end; only `"reportlab"` is supported.
`verbose`	When True and a `source_emission` is supplied, the per-band table adds the A-weighted band level (`LfT(DW)` plus the band A-weighting), whose energy sum is the boxed `LAT(DW)`.
`language`	Fiche language: `"en"` (default) or `"es"`.
`source_emission`	Optional `SourceEmission` (the source sound power `Lw` and directivity, plus an optional meteorological correction) that turns the attenuation breakdown into the boxed A-weighted downwind level at the receiver.

Returns: The written path as a str.

Raises

Exception	When
ValueError	If `engine` is not `"reportlab"`, `language` is unknown, or a supplied `source_emission` sound power does not match the number of frequency bands.
ImportError	If reportlab or matplotlib is not installed (`pip install "phonometry[report,plot]"`).

predicted_receiver_level

predicted_receiver_level(
    sound_power_level: ArrayLike,
    geometry: PropagationGeometry,
    *,
    frequencies: ArrayLike = (63.0, 125.0, 250.0, 500.0, 1000.0, 2000.0, 4000.0, 8000.0),
    ground: GroundFactors | None = None,
    barrier: Barrier | None = None,
    atmosphere: AtmosphericConditions | None = None,
    directivity: DirectivityCorrection | None = None,
    c0: float | None = None,
) -> NDArray[np.float64]

Predicted octave-band receiver level (ISO 9613-2:1996, Eq. (3)/(6)).

Composes the downwind octave-band sound pressure level:

L_{f T} (D W) = L_{W} + D_{c} - A, D_{c} = D_{i} + D_{Ω}

from the total attenuation outdoor_propagation_attenuation. When c0 is given, the meteorological correction Cmet (Eq. (21)/(22)) is subtracted band by band to approximate the long-term average level LfT(LT) (Eq. (6)); the standard applies Cmet to the A-weighted level, so this is a per-band convenience.

Parameters

Name	Description
`sound_power_level`	Octave-band sound power level `Lw`, in decibels (re 1 pW), one value per frequency.
`geometry`	Source-to-receiver geometry of the path (`PropagationGeometry`): the distance `d`, the two heights and the optional projected distance `dp`.
`frequencies`	Octave-band midband frequencies, in hertz.
`ground`	Ground factors of the three regions (`GroundFactors`); `None` is hard ground throughout.
`barrier`	Optional screening obstacle (`Barrier`).
`atmosphere`	Air temperature, humidity and pressure behind the atmospheric absorption term (`AtmosphericConditions`); `None` is the reference air of the tabulated coefficients.
`directivity`	Directivity correction `Dc = Di + DOmega` (`DirectivityCorrection`); `None` is an omnidirectional source in free space ( $D_{c} = 0$ ).
`c0`	Meteorological factor `C0`, in decibels; `None` returns the downwind level `LfT(DW)` ( $C_{met} = 0$ ).

Returns: Predicted octave-band level per frequency, in decibels.

PropagationGeometry

PropagationGeometry(
    distance: float,
    source_height: float,
    receiver_height: float,
    projected_distance: float | None = None,
)

Source-to-receiver geometry of the propagation path (ISO 9613-2:1996).

The three lengths every term of the method needs: the straight-line distance d of the divergence and atmospheric terms (Eq. (7)/(8)), and the two heights above the ground the ground effect of clause 7.3.1 and the meteorological correction of clause 8 are written in.

Parameters

Name	Description
`distance`	Straight-line source-to-receiver distance `d`, in metres.
`source_height`	Source height `hs` above ground, in metres.
`receiver_height`	Receiver height `hr` above ground, in metres.
`projected_distance`	Ground-plane projected distance `dp`, in metres; `None` defaults to $d^{2} - (h_{s} - h_{r})^{2}$ .

region_ground_factors

region_ground_factors(
    segment_lengths: ArrayLike,
    segment_ground_factors: ArrayLike,
    source_height: float,
    receiver_height: float,
) -> GroundFactors

Ground factors of the three regions from a path crossing several grounds.

ISO 9613-2:1996, 7.3.1 splits the ground projection of the path into a source region 30 $h_{s}$ long, a receiver region 30 $h_{r}$ long and whatever middle region is left between them, and asks for one ground factor per region. Where the path runs over ground of more than one kind, the standard does not say how to reduce the several factors to the three the method wants. ISO/TR 17534-3:2015, 6.2.5 settles it for quality-assured software: each region takes the mean of G weighted by the length of the ground projection it covers.

The ground projection of the path is the concatenation of the segments, so $d_{p}$ is their total length; give the segments in order from the source.

Parameters

Name	Description
`segment_lengths`	Length of each segment of the ground projection, in metres, ordered from the source; each must be positive.
`segment_ground_factors`	Ground factor `G` of each segment ([0, 1]), aligned with `segment_lengths`.
`source_height`	Source height `hs` above ground, in metres.
`receiver_height`	Receiver height `hr` above ground, in metres.

Returns: The GroundFactors of the source, middle and receiver regions.

Raises

Exception	When
ValueError	If the two sequences disagree in length or are empty, a length is not positive, a factor is outside `[0, 1]`, or a height is negative or not finite.

SourceEmission

SourceEmission(
    sound_power_level: ArrayLike,
    directivity_index: float = 0.0,
    d_omega: float = 0.0,
    cmet: float | None = None,
)

Source emission terms for the ISO 9613-2 downwind receiver level (Eq. (3)).

Passed to OutdoorAttenuation.report so the prediction fiche can box the A-weighted downwind level at the receiver from an octave-band attenuation breakdown. The level is composed as $L_{f T} (D W) = L_{W} + D_{c} - A$ with the directivity correction $D_{c} = D_{i} + D_{Ω}$ (ISO 9613-2:1996, Eq. (3)); an optional meteorological correction cmet is subtracted for the long-term average level (Eq. (6)).

This report-time object keeps the emission out of outdoor_propagation_attenuation (which stays purely an attenuation calculation), so the receiver level is a presentation concern of the fiche.

Parameters

Name	Description
`sound_power_level`	Octave-band source sound power level `Lw` (dB re 1 pW), one value per band of the attenuation result.
`directivity_index`	Source directivity index `Di`, in decibels.
`d_omega`	Solid-angle index `DOmega`, in decibels (see `directivity_omega` for the alternative ground method).
`cmet`	Optional meteorological correction `Cmet` (dB), obtained from `meteorological_correction`; `None` reports the downwind level `LfT(DW)` directly ( $C_{met} = 0$ ).

Created and maintained by José Manuel Requena Plens ORCID All projects