Source: https://jmrplens.github.io/phonometry/reference/api/building/building-prediction/ Building acoustic performance prediction (EN 12354-1/-2:2000). This is the **prediction** counterpart of the measurement modules ([`phonometry.lab_insulation`](/phonometry/reference/api/building/lab-insulation/) for laboratory `R`/`Ln` and [`phonometry.insulation`](/phonometry/reference/api/building/insulation/) for field `R'`/`L'n`). EN 12354 estimates the *in-situ* apparent performance of a building from the laboratory performance of its elements, adding the flanking transmission that a field measurement would capture but a laboratory measurement suppresses. Both parts have a *detailed* per-band model and a *simplified* single-number model. This module implements the **simplified single-number model** (Part 1 Clause 4.4, Part 2 Clause 4.3): it takes the weighted single-number ratings of the elements (`Rw` of walls/floors, `ΔRw`/`ΔLw` of linings/coverings and the `Kij` vibration-reduction indices of the junctions) and predicts the apparent weighted rating (`R'w` airborne, `L'n,w` impact). The simplified model is exact for `RA` and a good approximation for `R'w` (Part 1 Clause 4.4.1), with a reported standard deviation of about 2 dB (Clause 5). **Airborne, Formula (26).** The apparent weighted sound reduction index is the energetic sum of the direct path `Dd` and, for every flanking element, the three flanking paths `Ff`, `Df` and `Fd`: ```text R'w = -10 lg[ 10^(-RDd,w/10) + Σ 10^(-RFf,w/10) + Σ 10^(-RDf,w/10) + Σ 10^(-RFd,w/10) ] ``` with the direct path `RDd,w = Rs,w + ΔRDd,w` (Formula 27) and each flanking path (Formula 28a) `Rij,w = (Ri,w + Rj,w)/2 + ΔRij,w + Kij + 10 lg(Ss/(l0·lf))` where `l0 = 1 m` is the reference coupling length. **Junctions, Annex E.** The vibration reduction index `Kij` of rigid cross (E.3) and T (E.4) junctions, junctions with flexible interlayers (E.5), lightweight façade junctions (E.6), junctions of lightweight double-leaf walls with homogeneous elements (E.7) or with other coupled double-leaf walls (E.8), and corners / thickness changes (E.9) are empirical functions of the mass ratio `M = lg(m'⊥,i / m'i)`. A minimum value `Kij,min` follows from the Kij,min relation of Clause 4.4.2 (printed as Eq. (23) in the BS EN 12354-1:2000 edition). **Impact, Formula (21).** `L'n,w = Ln,w,eq − ΔLw + K` with the bare-floor equivalent level `Ln,w,eq` (Annex B `164 − 35 lg(m'/m'0)`), the covering improvement `ΔLw` (ISO 717-2) and the flanking correction `K` from Table 1. Clause citations refer to EN 12354-1:2000 (airborne) or EN 12354-2:2000 (impact). > Auto-generated from the source docstrings by `scripts/generate_api_docs.py` (`make api-docs`). Do not edit by hand. ## AirbornePredictionResult ```python AirbornePredictionResult( r_prime_w: float, r_direct_w: float, paths: tuple[PathContribution, ...], dominant: PathContribution, ) ``` Predicted apparent airborne insulation (EN 12354-1:2000, Formula 26). **Attributes** | Name | Description | | :--- | :--- | | `r_prime_w` | Apparent weighted sound reduction index `R'w`, in dB. | | `r_direct_w` | Direct-path weighted index `RDd,w`, in dB (Formula 27). | | `paths` | Per-path contributions in input order (direct path first, then the flanking paths as supplied), each with its share of the energy. | | `dominant` | The path carrying the most energy (`PathContribution`). | ### AirbornePredictionResult.plot() ```python AirbornePredictionResult.plot( ax: Axes | None = None, *, language: str = 'en', **kwargs: Any, ) -> Axes ``` Plot the per-path shares of the transmitted energy. Requires matplotlib (`pip install phonometry[plot]`); returns the `Axes`. ### AirbornePredictionResult.report() ```python AirbornePredictionResult.report( path: str, *, metadata: ReportMetadata | None = None, engine: str = 'reportlab', verbose: bool = False, language: str = 'en', ) -> str ``` Render a predicted airborne insulation report to a PDF (EN 12354-1). Writes a one-page **prediction** report for the predicted apparent sound reduction index `R'` between rooms estimated by the EN/ISO 12354-1:2000 simplified single-number model (Clause 4.4): a standard-basis line that states the sheet is a prediction from element data and not a measurement, an optional metadata header block, a two-panel body with the transmission-path table (the direct path and each flanking path's weighted index `Rij,w`) beside the per-path share-of-energy plot, the boxed predicted rating `R'w`, the prediction statement (with the model's ~2 dB standard deviation) and, when a requirement is supplied, a PASS/FAIL verdict (the apparent index passes at or above the requirement), followed by a footer. The applicable [`ReportMetadata`](/phonometry/reference/api/building/insulation/#reportmetadata) fields describe the predicted situation: `specimen` (the separating element), `area` (the separating-element area `Ss`), `source_volume` / `receiving_volume` (the room geometry), `client`, `manufacturer`, `test_room`, `laboratory` (the calculator / laboratory), `operator`, `report_id` and `test_date`. A summary of the flanking construction and the model assumptions is recorded in `notes` (free text), and `requirement` supplies the target `R'w`. **Parameters** | Name | Description | | :--- | :--- | | `path` | Destination path of the PDF file. | | `metadata` | Optional [`ReportMetadata`](/phonometry/reference/api/building/insulation/#reportmetadata); `None` produces a lightweight fiche (body, rating, statement, disclaimer). | | `engine` | Rendering back end; only `"reportlab"` is supported. | | `verbose` | When `True`, the path table also shows each path's share of the transmitted sound energy. | | `language` | Fiche language: `"en"` (default) or `"es"`. | **Returns:** The written `path` as a `str`. **Raises** | Exception | When | | :--- | :--- | | ValueError | If `engine` is unknown or `language` is not supported. | | ImportError | If reportlab is not installed (`pip install phonometry[report]`), or matplotlib is missing for the embedded figure (`pip install phonometry[plot]`). | ## combine_linings ```python combine_linings(delta_a: float, delta_b: float) -> float ``` Combine two lining improvements (EN 12354-1 Formulas 30/31). For two linings the total improvement is the larger value plus half the smaller: `ΔR = max(a, b) + min(a, b)/2`. For a single lining pass the other as `0`. :::note ISO 12354-1:2017 (Formulas (22)/(23)) adds a special case the 2000 edition implemented here does not have: when *both* linings are negative (each lining worsens the insulation), half is taken of the *higher* value instead, `ΔR = min(a, b) + max(a, b)/2`, so two degrading linings degrade further (e.g. −2 and −4 dB combine to −5 dB under the 2017 rule, −4 dB under the 2000 rule used here). ::: **Parameters** | Name | Description | | :--- | :--- | | `delta_a` | Improvement of the first lining, in dB. | | `delta_b` | Improvement of the second lining, in dB. | **Returns:** Combined `ΔR`/`ΔRij`, in dB. ## equivalent_impact_level ```python equivalent_impact_level(mass_per_area: float) -> float ``` Bare-floor equivalent weighted impact level `Ln,w,eq` (Part 2, Annex B). `Ln,w,eq = 164 − 35 lg(m'/m'0)` with `m'0 = 1 kg/m²`, the closed form used in the Annex E worked example for a homogeneous concrete floor. The Annex B relation is stated for homogeneous floors of 100 kg/m² to 600 kg/m²; outside that envelope the value is an extrapolation and a `UserWarning` is emitted. **Parameters** | Name | Description | | :--- | :--- | | `mass_per_area` | Mass per unit area `m'` of the bare floor, in kg/m² (must be positive; the Annex B relation covers 100-600 kg/m²). | **Returns:** `Ln,w,eq`, in dB. **Raises** | Exception | When | | :--- | :--- | | ValueError | If `mass_per_area` is not positive. | ## flanking_element ```python flanking_element( *, label: str, r_flanking: float, r_separating: float, k_ff: float, k_fd: float, k_df: float, separating_area: float, coupling_length: float, delta_r_ff: float = 0.0, delta_r_fd: float = 0.0, delta_r_df: float = 0.0, flanking_area: float | None = None, ) -> tuple[FlankingPath, FlankingPath, FlankingPath] ``` Build the three flanking paths (Ff, Df, Fd) of one flanking element. Convenience wrapper over [`flanking_path`](/phonometry/reference/api/building/building-prediction/#flanking_path) for the common case where a flanking element is essentially the same on the source and receiving side (Clause 4.4.1). Returns the `Ff`, `Df` and `Fd` paths that this element contributes across its junction with the separating element. **Kij,min (Clause 4.4.2).** When `flanking_area` is given, the mandatory floor `Kij ≥ Kij,min` is applied automatically per path: `KFf` is clamped to `10 lg[lf·l0·(2/SF)]` (both junction elements are the flanking element) and `KFd`/`KDf` to `10 lg[lf·l0·(1/SF + 1/Ss)]` (flanking and separating element), via [`junction_min_vibration_reduction`](/phonometry/reference/api/building/building-prediction/#junction_min_vibration_reduction). Without `flanking_area` the per-path floors cannot be formed from the available geometry, so the raw `k_ff`/`k_fd`/`k_df` are used unchanged; compute the floors yourself (or call [`flanking_path`](/phonometry/reference/api/building/building-prediction/#flanking_path) with `kij_min`) in that case to stay within Clause 4.4.2. **Parameters** | Name | Description | | :--- | :--- | | `label` | Base name; paths are labelled `"-Ff"` etc. | | `r_flanking` | Weighted sound reduction index of the flanking element. | | `r_separating` | Weighted sound reduction index of the separating element. | | `k_ff` | `KFf` vibration reduction index, in dB. | | `k_fd` | `KFd` vibration reduction index, in dB. | | `k_df` | `KDf` vibration reduction index, in dB. | | `separating_area` | Separating-element area `Ss`, in m². | | `coupling_length` | Junction coupling length `lf`, in m. | | `delta_r_ff` | Combined lining improvement for the Ff path, in dB. | | `delta_r_fd` | Combined lining improvement for the Fd path, in dB. | | `delta_r_df` | Combined lining improvement for the Df path, in dB. | | `flanking_area` | Flanking-element area `SF = Sf`, in m². Enables the automatic `Kij,min` clamp (Clause 4.4.2); `None` skips it. | **Returns:** The `(Ff, Df, Fd)` [`FlankingPath`](/phonometry/reference/api/building/building-prediction/#flankingpath) triple. **Raises** | Exception | When | | :--- | :--- | | ValueError | If a geometry value is not positive or an input is non-finite. | ## flanking_path ```python flanking_path( *, label: str, kind: Literal['Ff', 'Df', 'Fd'], r_source: float, r_receive: float, k_ij: float, separating_area: float, coupling_length: float, delta_r: float = 0.0, kij_min: float | None = None, ) -> FlankingPath ``` Build one flanking path `Rij,w` (EN 12354-1 Formula 28a). `Rij,w = (r_source + r_receive)/2 + delta_r + k_ij + 10 lg(Ss/(l0·lf))`. The two element indices depend on the path: for `Ff` both are the flanking element (`RF,w`, `Rf,w`); for `Fd` they are the flanking (source) and separating (receive) elements; for `Df` the separating (source) and flanking (receive) elements. When `kij_min` is given, `k_ij` is clamped up to it (`max(k_ij, kij_min)`) before the path is formed, enforcing the floor `Kij ≥ Kij,min` of Clause 4.4.2 (compute `kij_min` with [`junction_min_vibration_reduction`](/phonometry/reference/api/building/building-prediction/#junction_min_vibration_reduction)). Left as `None` the raw `k_ij` is used unchanged. **Parameters** | Name | Description | | :--- | :--- | | `label` | Human-readable path name. | | `kind` | `"Ff"`, `"Df"` or `"Fd"`. | | `r_source` | Weighted sound reduction index of the source-side element. | | `r_receive` | Weighted sound reduction index of the receive-side element. | | `k_ij` | Vibration reduction index of this path, in dB. | | `separating_area` | Area `Ss` of the separating element, in m². | | `coupling_length` | Junction coupling length `lf`, in m. | | `delta_r` | Combined lining improvement `ΔRij,w` for this path, in dB. | | `kij_min` | Optional `Kij,min` floor (Clause 4.4.2); `k_ij` is raised to it when it lies below. `None` disables the clamp. | **Returns:** The [`FlankingPath`](/phonometry/reference/api/building/building-prediction/#flankingpath). **Raises** | Exception | When | | :--- | :--- | | ValueError | If `kind` is unknown, areas/lengths are not positive, or any value is non-finite. | ## FlankingPath ```python FlankingPath(label: str, kind: Literal['Ff', 'Df', 'Fd'], r_ij_w: float) ``` One flanking transmission path (Ff, Df or Fd) of the simplified model. **Attributes** | Name | Description | | :--- | :--- | | `label` | Human-readable path name, e.g. `"floor-Ff"`. | | `kind` | Path type, one of `"Ff"`, `"Df"`, `"Fd"`. | | `r_ij_w` | Weighted flanking sound reduction index `Rij,w` of the path, in dB (EN 12354-1 Formula 28a). | ## impact_flanking_correction ```python impact_flanking_correction( separating_mass: float, flanking_mass: float, ) -> int ``` Flanking correction `K` from Table 1 (EN 12354-2:2000). Looks up `K` (dB) for the separating-floor mass and the mean mass of the homogeneous flanking elements, selecting the nearest tabulated row/column (the table is discrete; masses outside 100–900 / 100–500 kg/m² clamp to the nearest edge). **Parameters** | Name | Description | | :--- | :--- | | `separating_mass` | Mass per unit area of the separating floor, in kg/m². | | `flanking_mass` | Mean mass per unit area of the homogeneous flanking elements not covered by additional layers, in kg/m². | **Returns:** The correction `K`, in dB (a non-negative integer). **Raises** | Exception | When | | :--- | :--- | | ValueError | If a mass is not positive. | ## ImpactPredictionResult ```python ImpactPredictionResult( l_prime_n_w: float, ln_w_eq: float, delta_l_w: float, k_correction: float, ) ``` Predicted apparent impact insulation (EN 12354-2:2000, Formula 21). **Attributes** | Name | Description | | :--- | :--- | | `l_prime_n_w` | Apparent weighted normalized impact sound pressure level `L'n,w`, in dB. | | `ln_w_eq` | Bare-floor equivalent weighted level `Ln,w,eq`, in dB. | | `delta_l_w` | Weighted covering improvement `ΔLw`, in dB. | | `k_correction` | Flanking correction `K`, in dB (Table 1). | ### ImpactPredictionResult.plot() ```python ImpactPredictionResult.plot( ax: Axes | None = None, *, language: str = 'en', **kwargs: Any, ) -> Axes ``` Plot the Formula 21 terms and the resulting `L'n,w`. Requires matplotlib (`pip install phonometry[plot]`); returns the `Axes`. ### ImpactPredictionResult.report() ```python ImpactPredictionResult.report( path: str, *, metadata: ReportMetadata | None = None, engine: str = 'reportlab', verbose: bool = False, language: str = 'en', ) -> str ``` Render a predicted impact insulation report to a PDF (EN 12354-2). Writes a one-page **prediction** report for the predicted apparent normalized impact sound pressure level `L'n` estimated by the EN/ISO 12354-2:2000 simplified single-number model (Clause 4.3): a standard-basis line that states the sheet is a prediction from element data and not a measurement, an optional metadata header block, a two-panel body with the Formula (21) term table (the bare-floor equivalent level `Ln,w,eq`, the covering improvement `ΔLw` and the flanking correction `K`) beside the term plot, the boxed predicted rating `L'n,w`, the prediction statement (with the model's ~2 dB standard deviation) and, when a requirement is supplied, a PASS/FAIL verdict (the apparent level passes at or below the requirement, a lower impact level being better), followed by a footer. The applicable [`ReportMetadata`](/phonometry/reference/api/building/insulation/#reportmetadata) fields describe the predicted situation: `specimen` (the separating floor), `area` (the floor area), `mass_per_area` (the bare floor's mass per unit area), `receiving_volume` (the receiving-room geometry), `client`, `manufacturer`, `test_room`, `laboratory` (the calculator / laboratory), `operator`, `report_id` and `test_date`. A summary of the flanking construction and the model assumptions is recorded in `notes` (free text), and `requirement` supplies the target `L'n,w`. **Parameters** | Name | Description | | :--- | :--- | | `path` | Destination path of the PDF file. | | `metadata` | Optional [`ReportMetadata`](/phonometry/reference/api/building/insulation/#reportmetadata); `None` produces a lightweight fiche (body, rating, statement, disclaimer). | | `engine` | Rendering back end; only `"reportlab"` is supported. | | `verbose` | Accepted for a uniform `.report()` signature; the impact fiche has a single body layout, so it has no effect. | | `language` | Fiche language: `"en"` (default) or `"es"`. | **Returns:** The written `path` as a `str`. **Raises** | Exception | When | | :--- | :--- | | ValueError | If `engine` is unknown or `language` is not supported. | | ImportError | If reportlab is not installed (`pip install phonometry[report]`), or matplotlib is missing for the embedded figure (`pip install phonometry[plot]`). | ## junction_min_vibration_reduction ```python junction_min_vibration_reduction( coupling_length: float, s_i: float, s_j: float, ) -> float ``` Minimum vibration reduction index `Kij,min` (EN 12354-1 Clause 4.4.2). Printed as Formula (29) in the EN 12354-1:2000 edition. `Kij,min = 10 lg[ lf · l0 · (1/Si + 1/Sj) ]` with the reference coupling length `l0 = 1 m`. When the tabulated `Kij` is below this value, the minimum is used (Clause 4.4.2). **Parameters** | Name | Description | | :--- | :--- | | `coupling_length` | Common coupling length `lf` of the junction, in m. | | `s_i` | Area of element `i`, in m². | | `s_j` | Area of element `j`, in m². | **Returns:** `Kij,min`, in dB. **Raises** | Exception | When | | :--- | :--- | | ValueError | If any argument is not positive. | ## junction_vibration_reduction ```python junction_vibration_reduction( junction_type: JunctionType, path: PathKind, mass_ratio: float, *, frequency: float = 500.0, f1: float = 125.0, ) -> float ``` Vibration reduction index `Kij` of a junction (EN 12354-1 Annex E). Empirical `Kij` for common junctions as a function of the mass ratio `M = lg(mass_ratio)` where `mass_ratio = m'⊥,i / m'i` is the mass per unit area of the perpendicular element over that of the element carrying the path (Formula E.2). `path` selects the *through* branch (in-line elements, `K13`), the *corner* branch (`K12 = K23`) or, for double-leaf separating walls, the *double-leaf* branch (`K24`, the path between the two flanking legs across the double leaf). Supported `junction_type` values and their formulas: - `"rigid_cross"` (E.3): through `8,7 + 17,1 M + 5,7 M²`; corner `8,7 + 5,7 M²`. - `"rigid_t"` (E.4): through `5,7 + 14,1 M + 5,7 M²`; corner `5,7 + 5,7 M²`. - `"flexible_t"` (E.5, wall junction with flexible interlayers): through `5,7 + 14,1 M + 5,7 M² + 2·Δ1`; corner `5,7 + 5,7 M² + Δ1` with `Δ1 = 10 lg(f/f1)` for `f > f1` (else 0) and `f1 = 125 Hz` for the typical interlayer `E1/t1 ≈ 100 MN/m³`; double-leaf `K24 = 3,7 + 14,1 M + 5,7 M²` clamped to `−4 dB ≤ K24 ≤ 0 dB`. (The 2000 print states the clamp as "0 ≤ K24 ≤ −4 dB", an obvious misprint of the bounds' order.) - `"lightweight_facade"` (E.6): through `max(5 + 10 M, 5)`; corner `10 + 10 |M|`. - `"lightweight_double_homogeneous"` (E.7, lightweight double-leaf wall joined to homogeneous elements): through `max(10 + 20 M − 3,3 lg(f/fk), 10)`; corner `10 + 10 |M| + 3,3 lg(f/fk)`; double-leaf `K24 = 3,0 + 14,1 M + 5,7 M²` with `fk = 500 Hz`. The K24 path is carried by the homogeneous element crossing the double leaf, so its per-path `mass_ratio = m'⊥,i/m'i` is leaf-over-homogeneous and the validity condition (homogeneous over three times heavier than a leaf) reads `mass_ratio < 1/3`. (The 2000 print states this line as `3,0 − 14,1 M + 5,7 M²` in the *figure-axis* variable `M = lg(m2/m1)` of Figure E.9, contradicting the annex's own per-path definition of M; both forms are numerically identical, and ISO 12354-1:2017 E.3.5 prints the per-path form implemented here. See `docs/ERRATA.md`.) - `"lightweight_double_coupled"` (E.8, junction of lightweight coupled double-leaf walls): through `max(10 + 20 M − 3,3 lg(f/fk), 10)`; corner `10 + 10 |M| − 3,3 lg(f/fk)`; with `fk = 500 Hz`. - `"corner"` (E.9 A, two elements meeting at a corner): corner `K12 = max(15 |M| − 3, −2)` (`= K21`); the only path. - `"thickness_change"` (E.9 B, thickness change in an element): through `K12 = 5 M² − 5` (`= K21`); the only path. **Parameters** | Name | Description | | :--- | :--- | | `junction_type` | Junction geometry (see above). | | `path` | `"through"` (K13; also the single K12 path of a thickness change), `"corner"` (K12 = K23; also the single path of a corner) or `"double_leaf"` (K24). | | `mass_ratio` | `m'⊥,i / m'i`, the mass per unit area of the perpendicular element over that of the element carrying the path (must be positive). The same per-path convention applies to every branch, including both `double_leaf` (K24) branches. | | `frequency` | Frequency at which `Kij` is evaluated, in Hz; only the `"flexible_t"` (through/corner) and the E.7/E.8 lightweight double-leaf junctions are frequency dependent. Defaults to 500 Hz, the value used by the simplified model (Clause 4.4.2), at which the E.7/E.8 `lg(f/fk)` terms vanish. | | `f1` | Interlayer characteristic frequency for `"flexible_t"`, in Hz. | **Returns:** `Kij`, in dB. **Raises** | Exception | When | | :--- | :--- | | ValueError | If `mass_ratio` is not positive, `frequency`/`f1` are not positive, an unknown `junction_type`/`path` is given, the requested path does not exist for the junction, or the E.7 double-leaf branch is requested outside its `m2/m1 > 3` validity. | ## PathContribution ```python PathContribution(label: str, kind: str, r_w: float, fraction: float) ``` A transmission path with its share of the total transmitted energy. **Attributes** | Name | Description | | :--- | :--- | | `label` | Path name (`"Dd"` for the direct path). | | `kind` | `"Dd"`, `"Ff"`, `"Df"` or `"Fd"`. | | `r_w` | Weighted sound reduction index of the path, in dB. | | `fraction` | Fraction of the total transmitted sound energy carried by this path (0 to 1); the dominant path has the largest fraction. | ## predicted_airborne_insulation ```python predicted_airborne_insulation( *, r_direct: float, flanking_paths: Sequence[FlankingPath] = (), delta_r_direct: float = 0.0, ) -> AirbornePredictionResult ``` Predict the apparent airborne insulation `R'w` (EN 12354-1 Formula 26). Energetically combines the direct path `RDd,w = r_direct + delta_r_direct` (Formula 27) with the supplied flanking paths: ```text R'w = -10 lg[ 10^(-RDd,w/10) + Σ 10^(-Rij,w/10) ] ``` With no flanking paths the result equals the direct path `RDd,w`; each added path strictly lowers `R'w`. The result exposes every path's share of the transmitted energy so the dominant path is visible. **Parameters** | Name | Description | | :--- | :--- | | `r_direct` | Weighted sound reduction index of the separating element `Rs,w`, in dB. | | `flanking_paths` | Flanking paths (see [`flanking_element`](/phonometry/reference/api/building/building-prediction/#flanking_element)). May be empty for the direct-only case. | | `delta_r_direct` | Combined lining improvement `ΔRDd,w` on the separating element, in dB. | **Returns:** The [`AirbornePredictionResult`](/phonometry/reference/api/building/building-prediction/#airbornepredictionresult). **Raises** | Exception | When | | :--- | :--- | | ValueError | If any input is non-finite. | ## predicted_impact_insulation ```python predicted_impact_insulation( *, ln_w_eq: float, delta_l_w: float = 0.0, k_correction: float = 0.0, ) -> ImpactPredictionResult ``` Predict the apparent impact insulation `L'n,w` (EN 12354-2 Formula 21). `L'n,w = Ln,w,eq − ΔLw + K`. The bare-floor equivalent level may come from [`equivalent_impact_level`](/phonometry/reference/api/building/building-prediction/#equivalent_impact_level) and the flanking correction from [`impact_flanking_correction`](/phonometry/reference/api/building/building-prediction/#impact_flanking_correction). **Parameters** | Name | Description | | :--- | :--- | | `ln_w_eq` | Bare-floor equivalent weighted level `Ln,w,eq`, in dB. | | `delta_l_w` | Weighted covering improvement `ΔLw` (ISO 717-2), in dB. | | `k_correction` | Flanking correction `K` (Table 1), in dB. | **Returns:** The [`ImpactPredictionResult`](/phonometry/reference/api/building/building-prediction/#impactpredictionresult). **Raises** | Exception | When | | :--- | :--- | | ValueError | If any input is non-finite. | ## standardized_impact_level ```python standardized_impact_level(l_prime_n_w: float, volume: float) -> float ``` Standardized apparent impact level `L'nT,w` (EN 12354-2 Formula 3). `L'nT,w = L'n,w − 10 lg(0,16·V/(A0·T0)) = L'n,w − 10 lg(0,032·V)` with `A0 = 10 m²` and `T0 = 0,5 s`, the exact Formula (3) form. The standard's own Annex E.3 worked example rounds the factor to `10 lg(V/30)` (1/0,032 = 31,25 ≈ 30), 0,18 dB below the exact form; both round to the same integer rating in E.3. **Parameters** | Name | Description | | :--- | :--- | | `l_prime_n_w` | Apparent weighted normalized impact level `L'n,w`, dB. | | `volume` | Receiving-room volume `V`, in m³ (must be positive). | **Returns:** `L'nT,w`, in dB. **Raises** | Exception | When | | :--- | :--- | | ValueError | If `volume` is not positive. | ## standardized_level_difference ```python standardized_level_difference( r_prime_w: float, volume: float, separating_area: float, ) -> float ``` Standardized level difference `DnT,w` from `R'w` (EN 12354-1 Formula 5b). `DnT = R' + 10 lg(0,16·V/(T0·Ss)) = R' + 10 lg(0,32·V/Ss)` with `T0 = 0,5 s`, the exact Formula (5b) form, applied to the weighted single numbers of the simplified model (Clause 4.4). The Annex H.3 worked example rounds the factor to `10 lg(V/(3·Ss))` (1/0,32 = 3,125 ≈ 3), printing `52,2 + 1,6 = 53,8 dB` where the exact form gives 53,6 dB; both round to the same `DnT,w = 54 dB`. **Parameters** | Name | Description | | :--- | :--- | | `r_prime_w` | Apparent weighted sound reduction index `R'w`, in dB (see [`predicted_airborne_insulation`](/phonometry/reference/api/building/building-prediction/#predicted_airborne_insulation)). | | `volume` | Receiving-room volume `V`, in m³ (must be positive). | | `separating_area` | Separating-element area `Ss`, in m² (must be positive). | **Returns:** `DnT,w`, in dB. **Raises** | Exception | When | | :--- | :--- | | ValueError | If `volume` or `separating_area` is not positive. |