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

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

Field airborne sound insulation (ISO 16283-1:2014) and impact sound
insulation (ISO 16283-2), with single-number weighted ratings and
spectrum adaptation terms (ISO 717-1 airborne, ISO 717-2 impact).

**Field quantities (ISO 16283-1:2014).** From the energy-average sound
pressure levels in the source and receiving rooms this module forms the
level difference `D = L1 - L2` (Clause 3.12, Formula (1)), the
standardized level difference `DnT = D + 10 lg(T/T0)` with the
reference reverberation time `T0 = 0,5 s` (Clause 3.13, Formula (2)),
and the apparent sound reduction index
`R' = D + 10 lg(S/A)` with the Sabine equivalent absorption area
`A = 0,16 V / T` (Clause 3.14/3.15, Formula (4) and (5)). Source and
receiving levels may be supplied already averaged (one value per band) or
as several microphone positions, which are then energy-averaged with
`10 lg( (1/n) sum 10^(Li/10) )` (Clause 7.8, Formula (9)). All
quantities are evaluated per one-third-octave band over the core range
100 Hz to 3150 Hz (Clause 5), the caller having already applied any
background-noise correction (Clause 9.2).

**Weighted rating (ISO 717-1).** The reference-curve method of Clause 4.4
shifts the reference curve of Table 3 in 1 dB steps towards the measured
curve until the sum of unfavourable deviations (measured below the
shifted reference) is as large as possible but not more than 32,0 dB for
the 16 one-third-octave bands (100 Hz to 3150 Hz) or 10,0 dB for the 5
octave bands (125 Hz to 2000 Hz). The weighted rating (`Rw`, `R'w`,
`Dn,w`, `DnT,w` ...) is the shifted reference read at 500 Hz. The
spectrum adaptation terms are `C = XA1 - Xw` and `Ctr = XA2 - Xw`
with `XAj = -10 lg sum 10^((Lij - Xi)/10)` rounded to an integer, using
the A-weighted spectra No. 1 (pink noise, `C`) and No. 2 (urban traffic,
`Ctr`) of Table 4 (Clause 4.5, Formula (1) and (2)). Input levels are
reduced to one decimal place before use (Clause 4.4, footnote 1). The
reference values, spectra and shifting rule are identical in the 2013 and
2020 editions of ISO 717-1.

**Enlarged frequency ranges (ISO 717-1 Annex B; ISO 717-2 A.2.1 NOTE).**
When measurements cover an enlarged range, additional adaptation terms are
stated with the range as a subscript: `C50-3150`, `C50-5000`,
`C100-5000` (and the `Ctr` counterparts) with the Table B.1 spectra, and
`CI,50-2500` for impact. [`weighted_rating_extended`](/phonometry/reference/api/building/insulation/#weighted_rating_extended) and
[`weighted_impact_rating_extended`](/phonometry/reference/api/building/insulation/#weighted_impact_rating_extended) compute them alongside the core
rating. Both accept `one_decimal=True` for the "1/10 dB for the expression
of uncertainty" variant of Clauses 4.4/4.5 (reference-curve shift in 0,1 dB
steps and one-decimal reductions), which ISO 12999-1:2020 Annex B requires
when stating the uncertainty of single-number values.

**Field impact quantities (ISO 16283-2).** With the tapping machine as the
impact source this module forms, from the energy-average impact sound
pressure level `Li` in the receiving room, the standardized impact sound
pressure level `L'nT = Li - 10 lg(T/T0)` with `T0 = 0,5 s` (Clause
3.13, Formula (1)) and the normalized impact sound pressure level
`L'n = Li + 10 lg(A/A0)` with the Sabine absorption area `A = 0,16 V/T`
and the reference area `A0 = 10 m²` (Clause 3.14, Formula (2)). Levels
may be supplied already averaged or as several microphone positions, then
energy-averaged (Clause 7.8, Formula (10)), over the core one-third-octave
range 100 Hz to 3150 Hz (Clause 5.1).

**Field façade quantities (ISO 16283-3:2016).** With an outdoor sound
source this module forms, from the level 2 m in front of the façade
`L1,2m` and the receiving-room level `L2`, the level difference
`D2m = L1,2m - L2` (Clause 3.14), its standardized form
`D2m,nT = D2m + 10 lg(T/T0)` with `T0 = 0,5 s` (Clause 3.15) and
normalized form `D2m,n = D2m - 10 lg(A/A0)` with the Sabine absorption
area `A = 0,16 V/T` (Clause 3.17) and reference `A0 = 10 m²`
(Clause 3.16): the global loudspeaker / traffic quantities
`Dls,2m,*` / `Dtr,2m,*`. When a surface level `L1,s` (microphone on
the test element) with the element area `S` and volume are given it
forms the apparent sound reduction index
`R'45° = L1,s - L2 + 10 lg(S/A) - 1,5` for the loudspeaker element method
(Clause 3.12) or `R'tr,s = L1,s - L2 + 10 lg(S/A) - 3` for the
road-traffic element method (Clause 3.13). These quantities are defined by
unnumbered formulas inline in the Clause 3 terms; positions are
energy-averaged with the surface-level formula (Clause 9.5.1, Formula (7)).
Quantities are evaluated over the core one-third-octave range 100 Hz to
3150 Hz (Clause 5), optionally extended to 50-5000 Hz. The façade quantity
is airborne, so its single-number rating uses the **ISO 717-1 airborne**
reference curve and method (Clause 2, Annex F) via [`weighted_rating`](/phonometry/reference/api/building/insulation/#weighted_rating)
unchanged.

**Weighted impact rating (ISO 717-2).** The reference-curve method of
Clause 4.3 shifts the Table 3 impact reference curve towards the measured
curve until the sum of unfavourable deviations (here where the
**measurement exceeds** the reference, the sign opposite to airborne) is
as large as possible but not more than 32,0 dB (16 one-third-octave bands)
or 10,0 dB (5 octave bands). The rating (`Ln,w`, `L'n,w`, `L'nT,w`)
is the shifted reference read at 500 Hz, reduced by a further 5 dB for
octave bands (Clause 4.3.2). The spectrum adaptation term
`CI = Ln,sum - 15 - Ln,w` uses the energetic sum `Ln,sum` over
100 Hz to 2500 Hz (one-third octave) or 125 Hz to 2000 Hz (octave),
rounded to an integer (Clause A.2.1, Formulae (A.1) to (A.3)). The Table 3
reference values, the shifting rule and CI are identical in the 2013 and
2020 editions of ISO 717-2 (the 2020 edition only adds Annex D for the
rubber-ball heavy/soft impactor, out of scope here).

## airborne_insulation

```python
airborne_insulation(
    l1: Sequence[float] | np.ndarray,
    l2: Sequence[float] | np.ndarray,
    t2: Sequence[float] | np.ndarray,
    *,
    area: float | None = None,
    volume: float | None = None,
    t0: float = 0.5,
) -> AirborneInsulationResult
```

Field airborne sound insulation per ISO 16283-1:2014.

Computes, per frequency band, the level difference `D = L1 - L2`
(Formula (1)), the standardized level difference
`DnT = D + 10 lg(T/T0)` (Formula (2)) and, when the partition area
and receiving-room volume are given, the apparent sound reduction
index `R' = D + 10 lg(S/A)` with `A = 0,16 V / T` (Formula (4)
and (5)).

`l1` and `l2` may be one value per band (already energy-averaged)
or a two-dimensional `(positions, bands)` array, in which case the
positions are energy-averaged with Formula (9). The band levels are
assumed already corrected for background noise (Clause 9.2).

**Parameters**

| Name | Description |
| :--- | :--- |
| `l1` | Source-room sound pressure levels, in dB. |
| `l2` | Receiving-room sound pressure levels, in dB. |
| `t2` | Receiving-room reverberation time per band, in seconds. |
| `area` | Area `S` of the common partition, in m² (optional; required together with `volume` for `R'`). |
| `volume` | Receiving-room volume `V`, in m³ (optional; required together with `area` for `R'`). |
| `t0` | Reference reverberation time `T0`, in seconds (default 0,5 s for dwellings, Clause 3.13). |

**Returns:** [`AirborneInsulationResult`](/phonometry/reference/api/building/insulation/#airborneinsulationresult) with `d`, `dnt` and `r_prime` (the latter `None` unless `area` and `volume` are both given).

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If the band counts of `l1`, `l2` and `t2` differ, if only one of `area`/`volume` is supplied, if `t2`/`t0` are not positive, or if inputs are non-finite. |

## AirborneInsulationResult

```python
AirborneInsulationResult(
    d: np.ndarray,
    dnt: np.ndarray,
    r_prime: np.ndarray | None,
    l1: np.ndarray | None = None,
    l2: np.ndarray | None = None,
    t2: np.ndarray | None = None,
    t0: float | None = None,
)
```

Per-band field airborne sound insulation (ISO 16283-1:2014).

**Attributes**

| Name | Description |
| :--- | :--- |
| `d` | Level difference `D = L1 - L2` per band, in dB (Clause 3.12, Formula (1)). |
| `dnt` | Standardized level difference `DnT` per band, in dB (Clause 3.13, Formula (2)). |
| `r_prime` | Apparent sound reduction index `R'` per band, in dB (Clause 3.14, Formula (4)), or `None` when the partition area and receiving-room volume were not supplied. |
| `l1` | Energy-average source-room levels the quantities were formed from, in dB (after any position averaging, Formula (9)). Defaults to `None` for backward-compatible construction. |
| `l2` | Energy-average receiving-room levels, in dB. Defaults to `None`. |
| `t2` | Receiving-room reverberation time per band, in seconds. Defaults to `None`. |
| `t0` | Reference reverberation time `T0` used for `DnT`, in seconds. Defaults to `None`. |

### AirborneInsulationResult.plot()

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

Plot the per-band insulation quantities (`DnT`, `D`, `R'`).

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

### AirborneInsulationResult.report()

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

Render an ISO 16283-1 field airborne sound-insulation report to a PDF.

Writes the one-page field test report of ISO 16283-1:2014 Clause 14
in the layout of the recommended Annex B form: the standard-basis
line, an optional metadata header block (client, construction, room
volumes, partition area ...), the one-third-octave table beside the
measured-versus-shifted-reference curve, the boxed field rating
`DnT,w (C; Ctr)` or `R'w (C; Ctr)` (evaluated per ISO 717-1 over
the 16 core bands), the mandatory field-method statement, an optional
verdict row and a footer with the identity block and disclaimer.

**Parameters**

| Name | Description |
| :--- | :--- |
| `path` | Destination path of the PDF file. |
| `quantity` | The reported field quantity: `"dnt"` (default, the standardized level difference of Annex B Figure B.1) or `"r_prime"` (the apparent sound reduction index of Figure B.2; requires the result to carry `r_prime`). |
| `metadata` | Optional [`ReportMetadata`](/phonometry/reference/api/building/insulation/#reportmetadata); `None` produces a lightweight fiche (body, rating and disclaimer only). |
| `engine` | Rendering back end; only `"reportlab"` is supported. |
| `verbose` | When `True`, the table shows the measurement chain per band (energy-average `L1` and `L2`, reverberation time `T` and the quantity) instead of the two-column `f \| value` form; it requires the result to carry `l1`, `l2` and `t2` (populated by [`airborne_insulation`](/phonometry/reference/api/building/insulation/#airborne_insulation)). |
| `language` | Fiche language: `"en"` (default, English) or `"es"` (Spanish, with a comma decimal separator). |

**Returns:** The written `path` as a `str`.

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If `engine` or `quantity` is unknown, the selected quantity is not available, the result does not hold the 16 core one-third-octave bands (100 Hz to 3150 Hz) the ISO 717-1 rating needs, or `verbose=True` without the per-band chain. |
| ImportError | If reportlab is not installed (`pip install phonometry[report]`). |

## energy_average_level

```python
energy_average_level(
    levels: Sequence[float] | np.ndarray,
    axis: int = -1,
) -> np.ndarray | float
```

Energy-average sound pressure level (ISO 16283-1:2014, Formula (9)).

Combines sound pressure levels measured at several microphone
positions into `L = 10 lg( (1/n) sum_i 10^(Li/10) )`.

**Parameters**

| Name | Description |
| :--- | :--- |
| `levels` | Sound pressure levels, in dB, at the `n` positions to be averaged along `axis`. |
| `axis` | Axis over which to average (default the last axis). |

**Returns:** The energy-average level, in dB; a scalar `float` when the result is zero-dimensional, otherwise an array.

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If `levels` is empty or contains non-finite values. |

## ExtendedImpactRatingResult

```python
ExtendedImpactRatingResult(
    rating: float,
    ci: float,
    ci_50_2500: float | None,
    core: ImpactRatingResult,
)
```

Weighted impact rating with `CI,50-2500` (ISO 717-2:2020 A.2.1 NOTE).

Values are integers unless computed with `one_decimal=True`.

**Attributes**

| Name | Description |
| :--- | :--- |
| `rating` | Weighted impact rating (`Ln,w`, ...) from the core 100-3150 Hz bands, in dB. |
| `ci` | Core spectrum adaptation term `CI` (100-2500 Hz), in dB. |
| `ci_50_2500` | Enlarged-range term `CI,50-2500`, in dB, or `None` when the supplied bands do not cover 50-2500 Hz. |
| `core` | The integer-mode [`ImpactRatingResult`](/phonometry/reference/api/building/insulation/#impactratingresult) of the core bands (independent of `one_decimal`). |

## ExtendedWeightedRatingResult

```python
ExtendedWeightedRatingResult(
    rating: float,
    c: float,
    ctr: float,
    c_50_3150: float | None,
    c_50_5000: float | None,
    c_100_5000: float | None,
    ctr_50_3150: float | None,
    ctr_50_5000: float | None,
    ctr_100_5000: float | None,
    core: WeightedRatingResult,
)
```

Weighted rating with the enlarged-range adaptation terms (ISO 717-1 Annex B).

All values are integers unless the result was computed with
`one_decimal=True` (the "1/10 dB for the expression of uncertainty"
variant of Clauses 4.4/4.5), in which case they carry one decimal place.
An extended term is `None` when the supplied bands do not cover its
frequency range.

**Attributes**

| Name | Description |
| :--- | :--- |
| `rating` | Weighted rating (`Rw`, `R'w`, ...) from the core 100-3150 Hz bands, in dB. |
| `c` | Core spectrum adaptation term `C` (100-3150 Hz), in dB. |
| `ctr` | Core spectrum adaptation term `Ctr` (100-3150 Hz), in dB. |
| `c_50_3150` | `C50-3150`, in dB, or `None`. |
| `c_50_5000` | `C50-5000`, in dB, or `None`. |
| `c_100_5000` | `C100-5000`, in dB, or `None`. |
| `ctr_50_3150` | `Ctr,50-3150`, in dB, or `None`. |
| `ctr_50_5000` | `Ctr,50-5000`, in dB, or `None`. |
| `ctr_100_5000` | `Ctr,100-5000`, in dB, or `None`. |
| `core` | The integer-mode [`WeightedRatingResult`](/phonometry/reference/api/building/insulation/#weightedratingresult) of the core bands (independent of `one_decimal`), for plotting and the unfavourable-deviation sum. |

## facade_insulation

```python
facade_insulation(
    l1_2m: Sequence[float] | np.ndarray,
    l2: Sequence[float] | np.ndarray,
    t2: Sequence[float] | np.ndarray,
    *,
    area: float | None = None,
    volume: float | None = None,
    surface_level: Sequence[float] | np.ndarray | None = None,
    method: str = 'loudspeaker',
    t0: float = 0.5,
    frequencies: Sequence[float] | np.ndarray | None = None,
) -> FacadeInsulationResult
```

Field façade sound insulation per ISO 16283-3:2016.

Computes, per frequency band, the global-method level difference
`D2m = L1,2m - L2` (Clause 3.14), its standardized form
`D2m,nT = D2m + 10 lg(T/T0)` (Clause 3.15) and, when the
receiving-room volume is given, its normalized form
`D2m,n = D2m - 10 lg(A/A0)` with the Sabine equivalent absorption
area `A = 0,16 V/T` (Clause 3.17) and `A0 = 10 m²` (Clause 3.16).
When a surface level `L1,s` (microphone on the test element),
together with the element area `S` and the volume, is supplied it
also computes the apparent sound reduction index of the element
method: `R'45° = L1,s - L2 + 10 lg(S/A) - 1,5` for a loudspeaker
source (Clause 3.12) or `R'tr,s = L1,s - L2 + 10 lg(S/A) - 3` for a
road-traffic source (Clause 3.13). The defining formulas are unnumbered
inline in the Clause 3 terms.

`l1_2m`, `l2` and `surface_level` may be one value per band
(already energy-averaged) or a two-dimensional `(positions, bands)`
array, in which case the positions are energy-averaged with the
surface-level formula (Clause 9.5.1, Formula (7)). Band levels are
assumed already corrected for background
noise. The single-number rating uses the ISO 717-1 airborne reference
curve (Annex F); pass the desired 16-band quantity to
[`weighted_rating`](/phonometry/reference/api/building/insulation/#weighted_rating).

**Parameters**

| Name | Description |
| :--- | :--- |
| `l1_2m` | Outdoor sound pressure levels 2 m in front of the façade, in dB. |
| `l2` | Receiving-room sound pressure levels, in dB. |
| `t2` | Receiving-room reverberation time per band, in seconds. |
| `area` | Area `S` of the test element, in m² (optional; required with `volume` and `surface_level` for `R'`). |
| `volume` | Receiving-room volume `V`, in m³ (optional; required for `D2m,n` and for `R'`). |
| `surface_level` | Outdoor surface level `L1,s` on the test element, in dB (optional; required with `area` and `volume` for `R'`). |
| `method` | `"loudspeaker"` (45° incidence, -1,5 dB) or `"road_traffic"` (all-angle incidence, -3 dB); selects the `R'` correction (Clause 3.12 / 3.13). |
| `t0` | Reference reverberation time `T0`, in seconds (default 0,5 s for dwellings, Clause 3.15). |
| `frequencies` | Optional band centre frequencies, in Hz, carried on the result for plotting. |

**Returns:** [`FacadeInsulationResult`](/phonometry/reference/api/building/insulation/#facadeinsulationresult) with `d_2m`, `d_2m_nt`, `d_2m_n` (`None` unless `volume` is given) and `r_prime` (`None` unless `surface_level`, `area` and `volume` are all given).

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If band counts differ, if `method` is unknown, if `t2`/`t0`/`area`/`volume` are not positive, if `area` is given without `surface_level`, if `surface_level` and `area` are given without `volume`, if `frequencies` is given with a length that differs from the band count, or if inputs are non-finite. Supplying `surface_level` alone is not an error: `r_prime` simply stays `None`. |

## FacadeInsulationResult

```python
FacadeInsulationResult(
    d_2m: np.ndarray,
    d_2m_nt: np.ndarray,
    d_2m_n: np.ndarray | None,
    r_prime: np.ndarray | None,
    frequencies: np.ndarray | None = None,
)
```

Per-band field façade sound insulation (ISO 16283-3).

**Attributes**

| Name | Description |
| :--- | :--- |
| `d_2m` | Level difference `D2m = L1,2m - L2` per band, in dB (Clause 3.14; `Dls,2m` loudspeaker, `Dtr,2m` traffic). |
| `d_2m_nt` | Standardized level difference `D2m,nT = D2m + 10 lg(T/T0)` per band, in dB (Clause 3.15). |
| `d_2m_n` | Normalized level difference `D2m,n = D2m - 10 lg(A/A0)` per band, in dB (Clause 3.16), or `None` when the receiving-room volume was not supplied. |
| `r_prime` | Apparent sound reduction index `R'45°` (loudspeaker, Clause 3.12) or `R'tr,s` (road traffic, Clause 3.13) per band, in dB, or `None` unless a surface level together with the element area and receiving-room volume were supplied. |
| `frequencies` | Band centre frequencies, in Hz, or `None`. |

### FacadeInsulationResult.plot()

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

Plot the per-band façade insulation profile (ISO 16283-3).

Draws the standardized level difference and any other available
quantities (`D2m`, `D2m,n`, `R'`) against frequency. Requires
matplotlib (`pip install phonometry[plot]`); returns the
`Axes`.

### FacadeInsulationResult.report()

```python
FacadeInsulationResult.report(
    path: str,
    *,
    quantity: str = 'd_2m_nt',
    metadata: ReportMetadata | None = None,
    engine: str = 'reportlab',
    verbose: bool = False,
    language: str = 'en',
) -> str
```

Render an ISO 16283-3 field facade sound-insulation report to a PDF.

Writes the one-page field facade test report of ISO 16283-3:2016: the
standard-basis line, an optional metadata header block, the
one-third-octave table beside the measured-versus-shifted-reference
curve, the boxed ISO 717-1 field rating of the reported `quantity`
(`D2m,nT,w` for `d_2m_nt`, `D2m,n,w` for `d_2m_n` or
`R'45,w` for `r_prime`, each with `C; Ctr` and evaluated over the
16 core bands), the mandatory field-method statement, an optional
verdict row and a footer with the identity block and disclaimer.

**Parameters**

| Name | Description |
| :--- | :--- |
| `path` | Destination path of the PDF file. |
| `quantity` | The reported facade quantity: `"d_2m_nt"` (default, the standardized facade level difference `D2m,nT`), `"d_2m_n"` (the normalized facade level difference `D2m,n`; requires the result to carry `d_2m_n`) or `"r_prime"` (the apparent sound reduction index `R'45`; requires the result to carry `r_prime`). |
| `metadata` | Optional [`ReportMetadata`](/phonometry/reference/api/building/insulation/#reportmetadata); `None` produces a lightweight fiche (body, rating and disclaimer only). |
| `engine` | Rendering back end; only `"reportlab"` is supported. |
| `verbose` | When `True`, the table shows the ISO 717 evaluation per band (the reported quantity, the shifted reference and the unfavourable deviation) instead of the two-column `f \| value` form. |
| `language` | Fiche language: `"en"` (default, English) or `"es"` (Spanish, with a comma decimal separator). |

**Returns:** The written `path` as a `str`.

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If `engine` or `quantity` is unknown, the selected quantity is not available, or the result does not hold the 16 core one-third-octave bands (100 Hz to 3150 Hz) the ISO 717-1 rating needs. |
| ImportError | If reportlab is not installed (`pip install phonometry[report]`). |

## impact_improvement_adaptation_term

```python
impact_improvement_adaptation_term(
    delta_l: Sequence[float] | np.ndarray,
) -> int
```

Spectrum adaptation term `CI,Δ` of a floor covering (ISO 717-2:2020 A.2.2).

`CI,Δ = CI,r,0 − CI,r` (Formula (A.4)) with `CI,r,0 = −11 dB` (the
bare Table 4 reference floor) and `CI,r` the ISO 717-2 spectrum
adaptation term of the reference floor with the covering under test,
`Ln,r = Ln,r,0 − ΔL` (Formula (1)). Together with
[`weighted_impact_improvement`](/phonometry/reference/api/building/insulation/#weighted_impact_improvement) it yields the single-number reduction
for a flat spectrum, `ΔLlin = ΔLw + CI,Δ` (Formula (A.5)). ISO 16251-1
Clause 8 e) requires this term in the statement of results.

**Parameters**

| Name | Description |
| :--- | :--- |
| `delta_l` | The reduction of impact sound pressure level `ΔL` per band, in dB; 16 one-third-octave values from 100 Hz to 3150 Hz. |

**Returns:** The spectrum adaptation term `CI,Δ`, in dB (integer).

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If `delta_l` is not 16 one-third-octave values, or is non-finite. |

## impact_insulation

```python
impact_insulation(
    li: Sequence[float] | np.ndarray,
    t2: Sequence[float] | np.ndarray,
    *,
    volume: float | None = None,
    t0: float = 0.5,
) -> ImpactInsulationResult
```

Field impact sound insulation per ISO 16283-2 (tapping machine).

Computes, per frequency band, the standardized impact sound pressure
level `L'nT = Li - 10 lg(T/T0)` (Formula (1)) and, when the
receiving-room volume is given, the normalized impact sound pressure
level `L'n = Li + 10 lg(A/A0)` with the Sabine equivalent absorption
area `A = 0,16 V / T` (Formula (6)) and the reference absorption area
`A0 = 10 m²` (Formula (2)).

`li` may be one value per band (already energy-averaged) or a
two-dimensional `(positions, bands)` array, in which case the
positions are energy-averaged with Formula (10). The band levels are
assumed already corrected for background noise (Clause 9).

**Parameters**

| Name | Description |
| :--- | :--- |
| `li` | Energy-average impact sound pressure levels, in dB. |
| `t2` | Receiving-room reverberation time per band, in seconds. |
| `volume` | Receiving-room volume `V`, in m³ (optional; required for `L'n`). |
| `t0` | Reference reverberation time `T0`, in seconds (default 0,5 s for dwellings, Clause 3.13). |

**Returns:** [`ImpactInsulationResult`](/phonometry/reference/api/building/insulation/#impactinsulationresult) with `l_n_t` and `l_n` (the latter `None` unless `volume` is given).

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If the band counts of `li` and `t2` differ, if `t2`/`t0`/`volume` are not positive, or if inputs are non-finite. |

## ImpactInsulationResult

```python
ImpactInsulationResult(
    l_n_t: np.ndarray,
    l_n: np.ndarray | None,
    li: np.ndarray | None = None,
    t2: np.ndarray | None = None,
    t0: float | None = None,
)
```

Per-band field impact sound insulation (ISO 16283-2).

**Attributes**

| Name | Description |
| :--- | :--- |
| `l_n_t` | Standardized impact sound pressure level `L'nT = Li - 10 lg(T/T0)` per band, in dB (Clause 3.13, Formula (1)). |
| `l_n` | Normalized impact sound pressure level `L'n = Li + 10 lg(A/A0)` per band, in dB (Clause 3.14, Formula (2)), or `None` when the receiving-room volume was not supplied. |
| `li` | Energy-average impact sound pressure levels the quantities were formed from, in dB (after any position averaging, Formula (10)). Defaults to `None` for backward-compatible construction. |
| `t2` | Receiving-room reverberation time per band, in seconds. Defaults to `None`. |
| `t0` | Reference reverberation time `T0` used for `L'nT`, in seconds. Defaults to `None`. |

### ImpactInsulationResult.plot()

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

Plot the per-band impact levels (`L'nT` and, if present, `L'n`).

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

### ImpactInsulationResult.report()

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

Render an ISO 16283-2 field impact sound-insulation report to a PDF.

Writes the one-page field test report of ISO 16283-2:2020 Clause 14
in the layout of the recommended Annex C form: the standard-basis
line, an optional metadata header block, the one-third-octave table
beside the measured-versus-shifted-reference curve, the boxed field
rating `L'nT,w (CI)` or `L'n,w (CI)` (evaluated per ISO 717-2
over the 16 core bands), the mandatory field-method statement, an
optional verdict row and a footer with the identity block and
disclaimer.

**Parameters**

| Name | Description |
| :--- | :--- |
| `path` | Destination path of the PDF file. |
| `quantity` | The reported field quantity: `"l_n_t"` (default, the standardized level of Annex C Figure C.1) or `"l_n"` (the normalized level of Figure C.2; requires the result to carry `l_n`). |
| `metadata` | Optional [`ReportMetadata`](/phonometry/reference/api/building/insulation/#reportmetadata); `None` produces a lightweight fiche (body, rating and disclaimer only). |
| `engine` | Rendering back end; only `"reportlab"` is supported. |
| `verbose` | When `True`, the table shows the measurement chain per band (energy-average `Li`, reverberation time `T` and the quantity) instead of the two-column `f \| value` form; it requires the result to carry `li` and `t2` (populated by [`impact_insulation`](/phonometry/reference/api/building/insulation/#impact_insulation)). |
| `language` | Fiche language: `"en"` (default, English) or `"es"` (Spanish, with a comma decimal separator). |

**Returns:** The written `path` as a `str`.

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If `engine` or `quantity` is unknown, the selected quantity is not available, the result does not hold the 16 core one-third-octave bands (100 Hz to 3150 Hz) the ISO 717-2 rating needs, or `verbose=True` without the per-band chain. |
| ImportError | If reportlab is not installed (`pip install phonometry[report]`). |

## ImpactRatingResult

```python
ImpactRatingResult(
    rating: int,
    ci: int,
    unfavourable_sum: float,
    band_centers: np.ndarray | None = None,
    measured: np.ndarray | None = None,
    shifted_reference: np.ndarray | None = None,
    quantity: str = 'impact',
)
```

Single-number weighted impact rating and CI (ISO 717-2).

**Attributes**

| Name | Description |
| :--- | :--- |
| `rating` | Weighted impact rating (`Ln,w`, `L'n,w`, `L'nT,w`), the shifted reference read at 500 Hz, in dB (Clause 4.3; octave-band ratings include the -5 dB reduction of Clause 4.3.2). Integer. |
| `ci` | Spectrum adaptation term `CI` (Clause A.2.1), in dB. Integer. |
| `unfavourable_sum` | Sum of unfavourable deviations at the final shift, in dB (Clause 4.3); at most 32,0 (16 bands) or 10,0 (5 bands). |
| `band_centers` | Band centre frequencies of the measured curve, in Hz. Defaults to `None` for backward-compatible construction. |
| `measured` | The measured impact levels used for the rating (after the one-decimal reduction of Clause 4.3.1), in dB. Defaults to `None`. |
| `shifted_reference` | Table 3 impact reference curve after the final shift, in dB. Defaults to `None`. |
| `quantity` | Always `"impact"` (ISO 717-2), selecting the impact labels of the ISO 717 Annex C report. |

### ImpactRatingResult.plot()

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

Plot the measured curve vs the shifted reference (ISO 717-2).

Unfavourable deviations (measurement above the reference, the sign
opposite to airborne) are shaded and `Ln,w (CI)` annotated.
Requires matplotlib (`pip install phonometry[plot]`); returns the
`Axes`.

### ImpactRatingResult.report()

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

Render an ISO 717-2 impact-insulation fiche to a PDF.

Writes a one-page accredited-laboratory report for impact sound: the
standard-basis line, an optional metadata header block, the band
table beside the measured-versus-shifted-reference plot (the
result's own `plot`), the boxed `Ln,w (CI)` result, an
optional verdict row and a footer with the fixed disclaimer.

**Parameters**

| Name | Description |
| :--- | :--- |
| `path` | Destination path of the PDF file. |
| `metadata` | Optional [`ReportMetadata`](/phonometry/reference/api/building/insulation/#reportmetadata); `None` produces a prediction fiche (body, result and disclaimer only). |
| `engine` | Rendering back end; only `"reportlab"` is supported. |
| `verbose` | When `True`, the table uses the ISO 717 Annex C columns (frequency, measured value, shifted reference, unfavourable deviation) instead of the two-column `f \| value` table. |
| `language` | Fiche language: `"en"` (default, English) or `"es"` (Spanish, with a comma decimal separator). |
| `symbol` | The reported single-number quantity, as plain text: `"Ln,w"` (the default when `None`), `"L'n,w"` or `"L'nT,w"` per ISO 717-2 Table 1, so a field measurement is not mislabelled with the laboratory descriptor. |

**Returns:** The written `path` as a `str`.

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If `engine` is not `"reportlab"`, `symbol` is not a valid quantity-symbol shape, or the result was built without the per-band data (`band_centers`, `measured`, `shifted_reference`). |
| ImportError | If reportlab is not installed (`pip install phonometry[report]`). |

## ReportMetadata

```python
ReportMetadata(
    specimen: str | None = None,
    client: str | None = None,
    mounted_by: str | None = None,
    manufacturer: str | None = None,
    area: float | None = None,
    mass_per_area: float | None = None,
    source_volume: float | None = None,
    receiving_volume: float | None = None,
    room_volume: float | None = None,
    source_positions: int | None = None,
    receiver_positions: int | None = None,
    temperature: float | None = None,
    relative_humidity: float | None = None,
    source_temperature: float | None = None,
    source_relative_humidity: float | None = None,
    receiving_temperature: float | None = None,
    receiving_relative_humidity: float | None = None,
    pressure: float | None = None,
    tube_diameter: float | None = None,
    mic_spacing: float | None = None,
    thickness: float | None = None,
    test_room: str | None = None,
    instrumentation: str | None = None,
    calibration: str | None = None,
    mounting: str | None = None,
    measurement_standard: str | None = None,
    test_date: str | None = None,
    laboratory: str | None = None,
    operator: str | None = None,
    report_id: str | None = None,
    requirement: float | None = None,
    required_class: int | None = None,
    notes: str | None = None,
)
```

Descriptive metadata for the accredited ISO 717 report fiche.

All fields are optional (default `None`); the report renders only the
fields that are supplied, so a partially populated instance is valid. The
numeric fields are validated on construction by physical range: the
dimension, mass, volume and pressure fields must be finite and strictly
positive; the temperature and requirement fields need only be finite (0
degrees Celsius or below is a valid test condition, and a programme-loudness
target in LUFS is negative); and the relative-humidity fields must lie
within 0..100 %. A violation raises `ValueError`.

**Attributes**

| Name | Description |
| :--- | :--- |
| `specimen` | Specimen description printed in the header (the tested element, e.g. `"200 mm concrete wall"`). |
| `client` | Client the test was carried out for. |
| `mounted_by` | Who mounted the specimen in the test opening. |
| `manufacturer` | Manufacturer of the tested element. |
| `area` | Specimen area `S`, in m^2 (the free test opening area). |
| `mass_per_area` | Measured mass per unit area, in kg/m^2. |
| `source_volume` | Source-room volume, in m^3. |
| `receiving_volume` | Receiving-room volume, in m^3. |
| `room_volume` | Volume of the single room under test, in m^3. Room acoustics (ISO 3382-1/-2) characterises one enclosure rather than a source/receiving pair, and ISO 3382-2:2008 Clause 9 requires the room volume to be reported; the room-acoustics fiche prints it in the header. Distinct from the `source_volume`/`receiving_volume` pair, which describe a sound-transmission measurement. |
| `source_positions` | Number of source (loudspeaker/omnidirectional) positions used in the measurement, an integer (ISO 3382-1:2009 Table 1 and ISO 3382-2:2008 Clause 8 require reporting the number of source positions). Printed by the room-acoustics fiche. |
| `receiver_positions` | Number of microphone (receiver) positions used, an integer (ISO 3382-1:2009 Table 1 and ISO 3382-2:2008 Clause 8 require reporting the number of microphone positions). Printed by the room-acoustics fiche. |
| `temperature` | Air temperature during the test, in degrees Celsius (a single representative value; use the per-room fields below when the source and receiving rooms are reported separately). |
| `relative_humidity` | Relative humidity during the test, in %. |
| `source_temperature` | Source-room air temperature, in degrees Celsius. |
| `source_relative_humidity` | Source-room relative humidity, in %. |
| `receiving_temperature` | Receiving-room air temperature, in degrees Celsius. |
| `receiving_relative_humidity` | Receiving-room relative humidity, in %. |
| `pressure` | Ambient (static) air pressure during the test, in kPa. |
| `test_room` | Test-room / facility identification. |
| `instrumentation` | Identification and class of the instrumentation used (manufacturer, model, serial number), as free text. The occupational noise-exposure fiche prints it for ISO 9612:2009 Clause 15 c; when it is not supplied that fiche falls back to the result's own instrument class. |
| `calibration` | Calibration traceability, as free text (calibrator, date and result of the most recent verification, the before/after field checks). Printed by the occupational noise-exposure fiche (ISO 9612:2009 Clause 15 c). |
| `tube_diameter` | Impedance-tube inner diameter `d` (circular tube) or maximum lateral dimension (rectangular tube), in metres. Printed by the impedance-tube fiche (ISO 10534-2), where it fixes the upper plane-wave cut-on frequency. |
| `mic_spacing` | Microphone spacing `s` between the two measurement positions of the impedance tube, in metres. Printed by the impedance-tube fiche (ISO 10534-2), where it bounds the working frequency range. |
| `thickness` | Specimen thickness under the applied static load, in metres. Printed by the dynamic-stiffness fiche (EN 29052-1 / ISO 9052-1), where EN 29052-1:1992 Clause 9 b) requires reporting the thickness of the resilient layer under load; it is shown in millimetres. |
| `mounting` | Mounting condition of the specimen (e.g. the ISO 10140-1 mounting code or a short description). |
| `measurement_standard` | Measurement standard the spectrum was obtained under (e.g. `"ISO 10140-2"` or `"ISO 16283-1"`); it forms the report's standard-basis line together with the ISO 717 rating part. |
| `test_date` | Date of the test, as a free-form string. |
| `laboratory` | Testing laboratory / institute name (footer). |
| `operator` | Operator who carried out the test (footer signature line). |
| `report_id` | Report / test number (footer). |
| `requirement` | Target single-number value the verdict row compares the rating against, expressed in the rating's own unit (e.g. dB, a dimensionless absorption coefficient, sone, or a programme-loudness level in LUFS). It need only be finite (a loudness target in LUFS is negative), so its sign is not constrained. The pass direction is defined by each rating's `report` method: quantities where more is better (airborne insulation, absorption) pass at or above the requirement, and quantities where less is better (impact level, loudness, aircraft noise) pass at or below it; the programme-loudness fiche reads it as the target level and passes within a tolerance. |
| `required_class` | Target performance-class index for a class-compliance verdict (the IEC 61260-1 filter fiche): `0`, `1` or `2`, where class 0 is the strictest. When supplied, the fiche's verdict passes if the achieved overall class is at least as strict as this class (a smaller or equal class index). `None` (the default) prints no verdict row. |
| `notes` | Free-form remarks printed in the footer. |

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If a supplied dimension/mass/volume/pressure is not finite and strictly positive, a temperature or requirement is not finite, a relative humidity is outside 0..100 %, or a required class is not one of 0, 1, 2, or a position count is not a finite, positive integer. |

### ReportMetadata.is_empty()

```python
ReportMetadata.is_empty() -> bool
```

Return `True` when no field is set (an all-`None` instance).

## weighted_impact_improvement

```python
weighted_impact_improvement(delta_l: Sequence[float] | np.ndarray) -> int
```

Weighted reduction of impact sound pressure level `ΔLw` (ISO 717-2:2020 §5).

Relates a measured improvement spectrum `ΔL` to the heavyweight reference
floor of Table 4: the reference level with the covering is
`Ln,r = Ln,r,0 − ΔL` (Formula (1)) and the weighted improvement is
`ΔLw = Ln,r,0,w − Ln,r,w = 78 − Ln,r,w` (Formula (2)), where `Ln,r,w` is
the ISO 717-2 weighted rating of `Ln,r` from [`weighted_impact_rating`](/phonometry/reference/api/building/insulation/#weighted_impact_rating).

**Parameters**

| Name | Description |
| :--- | :--- |
| `delta_l` | The reduction of impact sound pressure level `ΔL` per band, in dB; 16 one-third-octave values from 100 Hz to 3150 Hz (e.g. from a floor-covering measurement to ISO 10140-3 or ISO 16251-1). |

**Returns:** The weighted reduction `ΔLw`, in dB (rounded, per ISO 717-2).

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If `delta_l` is not 16 one-third-octave values, or is non-finite. |

## weighted_impact_rating

```python
weighted_impact_rating(
    values_by_band: Sequence[float] | np.ndarray,
    bands: str | None = None,
) -> ImpactRatingResult
```

Single-number weighted impact rating and CI per ISO 717-2.

Applies the reference-curve method of Clause 4.3: the Table 3 impact
reference curve is shifted in 1 dB steps towards the measured curve
until the sum of unfavourable deviations is as large as possible but
not more than 32,0 dB (16 one-third-octave bands, 100 Hz to 3150 Hz)
or 10,0 dB (5 octave bands, 125 Hz to 2000 Hz). For impact sound an
unfavourable deviation occurs where the **measurement exceeds** the
reference (the sign opposite to ISO 717-1 airborne). The rating is the
shifted reference read at 500 Hz; for octave bands it is then reduced
by 5 dB (Clause 4.3.2). The spectrum adaptation term `CI` follows
Clause A.2.1. Input values are first reduced to one decimal place
(Clause 4.3.1, footnote 1).

The shift search reuses the verified engine of [`weighted_rating`](/phonometry/reference/api/building/insulation/#weighted_rating)
on the negated curves: minimising `Σ max(0, measured - (ref + k))`
over `k` equals maximising `Σ max(0, (-ref) + (-k) - (-measured))`,
the airborne problem, so no separate search is duplicated.

**Parameters**

| Name | Description |
| :--- | :--- |
| `values_by_band` | Measured impact levels (`Ln`, `L'n`, `L'nT`) in dB. 16 values are read as one-third-octave bands, 5 values as octave bands. |
| `bands` | `"third-octave"`, `"octave"` or `None` to infer the band set from the number of values. |

**Returns:** [`ImpactRatingResult`](/phonometry/reference/api/building/insulation/#impactratingresult) with `rating`, `ci` and `unfavourable_sum`.

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If the number of values does not match the band set, or if any value is non-finite. |

## weighted_impact_rating_extended

```python
weighted_impact_rating_extended(
    values_by_band: Sequence[float] | np.ndarray,
    frequencies: Sequence[float] | np.ndarray | None = None,
    *,
    one_decimal: bool = False,
) -> ExtendedImpactRatingResult
```

Weighted impact rating with `CI,50-2500` (ISO 717-2:2020 A.2.1).

Computes the weighted impact rating from the core one-third-octave bands
100-3150 Hz (Clause 4.3) and, when the input covers 50-2500 Hz, the
enlarged-range spectrum adaptation term `CI,50-2500` of the A.2.1 NOTE:
the energetic sum runs over 50-2500 Hz instead of 100-2500 Hz in
Formula (A.1), `CI = Ln,sum − 15 − Ln,w`.

With `one_decimal=True` the reference-curve shift runs in 0,1 dB steps
and the sums keep one decimal place (Clauses 4.3.1/4.4; e.g. the
reference floor yields `Ln,r,0,w = 77,6 dB` and `CI,r,0 = −10,3 dB`
as printed in A.2.2).

**Parameters**

| Name | Description |
| :--- | :--- |
| `values_by_band` | Measured impact levels (`Ln`, `L'n`, `L'nT`) in dB, one-third-octave bands. |
| `frequencies` | Band centre frequencies, in Hz (one per value). `None` assumes exactly the 16 core bands 100-3150 Hz. |
| `one_decimal` | Use the 0,1 dB shift and one-decimal reductions. |

**Returns:** An [`ExtendedImpactRatingResult`](/phonometry/reference/api/building/insulation/#extendedimpactratingresult).

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If the input is not one-dimensional and finite, the band counts differ, or the core bands are missing. |

## weighted_rating

```python
weighted_rating(
    values_by_band: Sequence[float] | np.ndarray,
    bands: str | None = None,
) -> WeightedRatingResult
```

Single-number weighted rating and C / Ctr per ISO 717-1.

Applies the reference-curve method of Clause 4.4: the Table 3
reference curve is shifted in 1 dB steps towards the measured curve
until the sum of unfavourable deviations is as large as possible but
not more than 32,0 dB (16 one-third-octave bands, 100 Hz to 3150 Hz)
or 10,0 dB (5 octave bands, 125 Hz to 2000 Hz). The rating is the
shifted reference read at 500 Hz. The spectrum adaptation terms
`C` and `Ctr` follow Clause 4.5 with the Table 4 spectra No. 1 and
No. 2. Input values are first reduced to one decimal place
(Clause 4.4, footnote 1).

**Parameters**

| Name | Description |
| :--- | :--- |
| `values_by_band` | Measured band quantities (`R`, `R'`, `Dn`, `DnT` ...) in dB. 16 values are read as one-third-octave bands, 5 values as octave bands. |
| `bands` | `"third-octave"`, `"octave"` or `None` to infer the band set from the number of values. |

**Returns:** [`WeightedRatingResult`](/phonometry/reference/api/building/insulation/#weightedratingresult) with `rating`, `c`, `ctr` and `unfavourable_sum`.

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If the number of values does not match the band set, or if any value is non-finite. |

## weighted_rating_extended

```python
weighted_rating_extended(
    values_by_band: Sequence[float] | np.ndarray,
    frequencies: Sequence[float] | np.ndarray | None = None,
    *,
    one_decimal: bool = False,
) -> ExtendedWeightedRatingResult
```

Weighted rating with enlarged-range adaptation terms (ISO 717-1 Annex B).

Computes the weighted rating from the core one-third-octave bands
100-3150 Hz (Clause 4.4) and, for every enlarged frequency range covered
by the input, the additional spectrum adaptation terms of Annex B
(`C50-3150`, `C50-5000`, `C100-5000` and the `Ctr` counterparts)
with the Table B.1 spectra: `Cj = XAj − Xw` where `XAj` sums over the
bands of the enlarged range (Clause 4.5 with Annex B).

With `one_decimal=True` the reference-curve shift runs in 0,1 dB steps
and every reduction keeps one decimal place; the variant Clauses 4.4/4.5
prescribe "for the expression of uncertainty" and ISO 12999-1:2020
Annex B requires for the uncertainty of single-number values.

**Parameters**

| Name | Description |
| :--- | :--- |
| `values_by_band` | Measured band quantities (`R`, `R'`, `Dn`, `DnT` ...) in dB, one-third-octave bands. |
| `frequencies` | Band centre frequencies, in Hz (one per value). `None` assumes exactly the 16 core bands 100-3150 Hz. The 16 core bands must always be present; extended terms are formed for each Annex B range whose bands are all present. |
| `one_decimal` | Use the 0,1 dB shift and one-decimal reductions. |

**Returns:** An [`ExtendedWeightedRatingResult`](/phonometry/reference/api/building/insulation/#extendedweightedratingresult).

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If the input is not one-dimensional and finite, the band counts differ, or the core bands are missing. |

## WeightedRatingResult

```python
WeightedRatingResult(
    rating: int,
    c: int,
    ctr: int,
    unfavourable_sum: float,
    band_centers: np.ndarray | None = None,
    measured: np.ndarray | None = None,
    shifted_reference: np.ndarray | None = None,
    quantity: str = 'airborne',
)
```

Single-number weighted rating and adaptation terms (ISO 717-1).

**Attributes**

| Name | Description |
| :--- | :--- |
| `rating` | Weighted rating (`Rw`, `R'w`, `DnT,w` ...), the shifted reference read at 500 Hz, in dB (Clause 4.4). Integer. |
| `c` | Spectrum adaptation term `C` (spectrum No. 1), in dB (Clause 4.5). Integer. |
| `ctr` | Spectrum adaptation term `Ctr` (spectrum No. 2), in dB (Clause 4.5). Integer. |
| `unfavourable_sum` | Sum of unfavourable deviations at the final shift, in dB (Clause 4.4); at most 32,0 (16 bands) or 10,0 (5 bands). |
| `band_centers` | Band centre frequencies of the measured curve, in Hz. Defaults to `None` for backward-compatible construction. |
| `measured` | The measured band quantities used for the rating (after the one-decimal reduction of Clause 4.4), in dB. Defaults to `None`. |
| `shifted_reference` | Table 3 reference curve after the final shift, in dB. Defaults to `None`. |
| `quantity` | `"airborne"` (ISO 717-1, sound reduction index) or `"impact"` (ISO 717-2), selecting the labels of the ISO 717 Annex C report. Defaults to `"airborne"`. |

### WeightedRatingResult.plot()

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

Plot the measured curve vs the shifted reference (ISO 717-1).

Unfavourable deviations (reference above measurement) are shaded and
`Rw (C; Ctr)` annotated. Requires matplotlib
(`pip install phonometry[plot]`); returns the
`Axes`.

### WeightedRatingResult.report()

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

Render an ISO 717-1 airborne sound-insulation fiche to a PDF.

Writes a one-page accredited-laboratory report: the standard-basis
line, an optional metadata header block, the band table beside the
measured-versus-shifted-reference plot (the result's own
`plot`), the boxed `Rw (C; Ctr)` result, an optional verdict
row and a footer with the fixed disclaimer.

**Parameters**

| Name | Description |
| :--- | :--- |
| `path` | Destination path of the PDF file. |
| `metadata` | Optional [`ReportMetadata`](/phonometry/reference/api/building/insulation/#reportmetadata); `None` produces a prediction fiche (body, result and disclaimer only). |
| `engine` | Rendering back end; only `"reportlab"` is supported. |
| `verbose` | When `True`, the table uses the ISO 717 Annex C columns (frequency, measured value, shifted reference, unfavourable deviation) instead of the two-column `f \| value` table. |
| `language` | Fiche language: `"en"` (default, English) or `"es"` (Spanish, with a comma decimal separator). |
| `symbol` | The reported single-number quantity, as plain text: `"Rw"` (the default when `None`), `"R'w"`, `"Dn,w"`, `"DnT,w"` ... per ISO 717-1 Tables 1-2, so a field measurement (e.g. a standardized level difference rated to `DnT,w`) is not mislabelled with the laboratory descriptor. |

**Returns:** The written `path` as a `str`.

**Raises**

| Exception | When |
| :--- | :--- |
| ValueError | If `engine` is not `"reportlab"`, `symbol` is not a valid quantity-symbol shape, or the result was built without the per-band data (`band_centers`, `measured`, `shifted_reference`). |
| ImportError | If reportlab is not installed (`pip install phonometry[report]`). |
