---
title: "building.building_prediction"
description: "Public API of phonometry.building.building_prediction (auto-generated)."
sidebar:
  label: "building_prediction"
---

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

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).

## 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`.

**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 `"<label>-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 Eq. (23) in the BS 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` (given only for `m2/m1 > 3`); with
  `fk = 500 Hz`.
- `"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` (must be positive). |
| `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. |
