building.prediction.detailed_model

Detailed per-band building prediction (EN/ISO 12354-1/-2:2017).

This is the detailed model of the building-prediction chain, the per-band counterpart of the simplified single-number model implemented in phonometry.building.prediction.simplified_model. Where the simplified model combines the weighted ratings of the elements (Rw, ΔRw, Kij) into a single R'w / L'n,w, the detailed model carries every quantity through the one-third-octave (or octave) bands, converts the laboratory element data to their in-situ values, forms each transmission path per band and only then rates the result through ISO 717. It is what a consultant runs when the element spectra are known and the dominant path per band matters.

Chain, airborne (ISO 12354-1:2017, Clause 4.2).

1. Element data per band. For homogeneous elements the sound reduction index follows from the material properties with the Annex B model: the radiation factor for free bending waves σ (Formulae B.4 to B.6, bending_radiation_factor), the radiation factor for forced waves σf (Formula B.3, forced_radiation_factor) and the three-branch transmission factor of Formula (B.2) (calculated_sound_reduction_index).

2. In-situ conversion (Clause 4.2.2). The total loss factor in situ follows from Annex C Formula (C.1),

   $${\eta }_{\mathrm{tot}}={\eta }_{\mathrm{int}}+\frac{2{\rho }_o{c}_o\sigma }{2\pi f{m}^{\prime }}+\frac{c_o}{{\pi }^{2}S\sqrt{f{f}_{\mathrm{c}}}}\sum _k{l}_k{\alpha }_k$$

   (in_situ_total_loss_factor), with the perimeter absorption coefficients deduced from the junctions’ vibration reduction indices (Formula C.4, perimeter_absorption_coefficient). From it come the structural reverberation time $T_{\mathrm{s}}=2.2/(f{\eta }_{\mathrm{tot}})$ (structural_reverberation_time), the in-situ index $R_{\mathrm{situ}}=R-10{\log }_{10}(T_{\mathrm{s},\mathrm{situ}}/T_{\mathrm{s},\mathrm{lab}})$ (Formula 9, in_situ_reduction_index) and the equivalent absorption length $a_{\mathrm{situ}}=2.2{\pi }^{2}S\sqrt{f_{\mathrm{ref}}/f}/(c_o{T}_{\mathrm{s},\mathrm{situ}})$ (Formula 11).

3. Junctions (Formula 10). $D_{v,ij,\mathrm{situ}}=K_{ij}-10{\log }_{10}(l_{ij}/\sqrt{a_{i,\mathrm{situ}}{a}_{j,\mathrm{situ}}})$, floored at 0 dB (in_situ_velocity_level_difference).

4. Paths. The direct path is $R_{\mathrm{Dd}}=R_{\mathrm{s},\mathrm{situ}}+\Delta R_{\mathrm{D},\mathrm{situ}}+\Delta R_{\mathrm{d},\mathrm{situ}}$ (Formula 14) and each flanking path (Formula 15) is $R_{ij}=R_{i,\mathrm{situ}}/2+\Delta R_{i,\mathrm{situ}}+R_{j,\mathrm{situ}}/2+\Delta R_{j,\mathrm{situ}}+D_{v,ij,\mathrm{situ}}+T$ with the geometry term $T=10{\log }_{10}(S_{\mathrm{s}}/\sqrt{S_i{S}_j})$ (flanking_reduction_index).

5. Assembly. $R^{\prime }=-10{\log }_{10}(\sum 10^{-R/10})$ over the direct path and all flanking paths (Formulae 1 to 4), then R'w (C; Ctr) per ISO 717-1 (detailed_airborne_prediction).

Chain, impact (ISO 12354-2:2017, Clause 4.2). The bare floor’s normalized impact sound pressure level per band follows from Annex B Formula (B.2), $L_{\mathrm{n}}=155-30{\log }_{10}(m^{\prime })+10{\log }_{10}(T_{\mathrm{s}})+10{\log }_{10}(\sigma )+10{\log }_{10}(f/f_{\mathrm{ref}})$ (bare_floor_impact_level); the direct path is $L_{\mathrm{n},\mathrm{d}}=L_{\mathrm{n},\mathrm{situ}}-\Delta L_{\mathrm{situ}}-\Delta L_{\mathrm{d},\mathrm{situ}}$ (Formula 11) and each flanking path (Formula 12) is $L_{\mathrm{n},ij}=L_{\mathrm{n},\mathrm{situ}}-\Delta L_{\mathrm{situ}}+(R_{i,\mathrm{situ}}-R_{j,\mathrm{situ}})/2-\Delta R_{j,\mathrm{situ}}-D_{v,ij,\mathrm{situ}}-10{\log }_{10}(S_i/\sqrt{S_i{S}_j})$ (flanking_impact_level), combined energetically into L'n and rated L'n,w (CI) per ISO 717-2 (detailed_impact_prediction).

The two parts share the same in-situ machinery, so a building is described once (HomogeneousElement per element, in_situ_element per band) and both the airborne and the impact chain read the same InSituElementResult.

Type A and Type B elements. HomogeneousElement and in_situ_element describe a Type A element, one whose structural reverberation time is set by the elements connected to it. For a Type B element the standard takes $T_{\mathrm{s},\mathrm{situ}}=T_{\mathrm{s},\mathrm{lab}}$ (so no in-situ transfer is needed) and describes the junction with the normalized direction-averaged velocity level difference Dv,ij,n instead of Kij, or with a laboratory measurement of the flanking level difference Dn,f. Those branches are flanking_reduction_index_from_normalized_difference (Formula 17), flanking_impact_level_from_normalized_difference (Part 2, Formula 14) and flanking_reduction_index_from_flanking_level (Formula 16), with resonant_sound_reduction_index for the Annex B.1 correction their element indices need below fc.

Clause and formula citations refer to ISO 12354-1:2017 (airborne) or ISO 12354-2:2017 (impact). The worked example of ISO 12354-1:2017 Annex L and ISO 12354-2:2017 Annex G (one heavy homogeneous building driving both parts) is reproduced band by band in the test suite; the defects found in its printed tables are recorded in docs/ERRATA.md.

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

airborne_flanking_path

airborne_flanking_path(
    *,
    label: str,
    kind: FlankingKind,
    element_i: InSituElementResult,
    element_j: InSituElementResult,
    vibration_reduction_index: ArrayLike,
    coupling_length: float,
    separating_area: float,
    delta_r_i: ArrayLike = 0.0,
    delta_r_j: ArrayLike = 0.0,
) -> BandPath

Build one airborne flanking path from two in-situ elements (Formula 15).

The junction velocity level difference is formed from the two elements’ equivalent absorption lengths with Formula (10), then Formula (15) gives Rij per band.

Parameters

Name	Description
label	Human-readable path name.
kind	"Ff", "Df" or "Fd".
element_i	The element excited in the source room.
element_j	The element radiating in the receiving room.
vibration_reduction_index	Kij of this path (per band or a single value), in dB.
coupling_length	Common coupling length lij, in m.
separating_area	Separating-element area Ss, in m².
delta_r_i	ΔRi,situ on element i, per band, in dB.
delta_r_j	ΔRj,situ on element j, per band, in dB.

Returns: The BandPath carrying Rij.

Raises

Exception	When
ValueError	If kind is unknown or a geometry value is not positive.

BandPath

BandPath(label: str, kind: str, values: np.ndarray)

One transmission path of the detailed model, per band.

Attributes

Name	Description
label	Human-readable path name, e.g. "ext wall 1-Df".
kind	"Dd", "Ff", "Df" or "Fd".
values	Rij (airborne) or Ln,ij (impact) per band, in dB.

bare_floor_impact_level

bare_floor_impact_level(
    frequencies: ArrayLike,
    *,
    mass_per_area: float,
    structural_reverberation_time: ArrayLike,
    radiation_factor: ArrayLike,
) -> np.ndarray

Normalized impact level of a bare monolithic floor (Part 2, F. B.2).

$$L_{\mathrm{n}}=155-30{\log }_{10}(m^{\prime }/1kg/{\mathrm{m}}^2)+10{\log }_{10}(T_{\mathrm{s}}/1\mathrm{s})+10{\log }_{10}\sigma +10{\log }_{10}(f/f_{\mathrm{ref}})$$

with $f_{\mathrm{ref}}=1000$ Hz, the closed form obtained with the force level of the standard tapping machine on a low-mobility floor. Supplying the in-situ structural reverberation time and radiation factor returns Ln,situ directly.

The reciprocity relation of Part 2 Formulae (B.3)/(B.4), $R+L_{\mathrm{n}}=38+30{\log }_{10}f$ in one-third-octave bands (43 in octave bands), holds where forced transmission is negligible and gives an independent check on the pair.

Parameters

Name	Description
frequencies	Band centre frequencies f, in Hz.
mass_per_area	Mass per unit area m' of the floor, in kg/m².
structural_reverberation_time	Structural reverberation time Ts per band, in s.
radiation_factor	Radiation factor for free bending waves σ per band.

Returns: The normalized impact sound pressure level Ln per band, in dB.

Raises

Exception	When
ValueError	If an input is not positive/finite or the per-band arrays do not share the band count.

bending_radiation_factor

bending_radiation_factor(
    frequencies: ArrayLike,
    *,
    critical_frequency: float,
    length1: float,
    length2: float,
    speed_of_sound: float = 340.0,
) -> np.ndarray

Radiation factor for free bending waves σ (Formulae B.4 to B.6).

The three candidate factors of Formula (B.4) are

• ${\sigma }_1=1/\sqrt{1-f_{\mathrm{c}}/f}$ (above the critical frequency),
• ${\sigma }_2=4l_1{l}_2(f/c_o{)}^2$ (the plate acting as a small piston),
• ${\sigma }_3=\sqrt{2\pi f(l_1+l_2)/(16c_o)}$ (corner and edge modes),

and the first plate mode $f_{11}=c_o^2/(4f_{\mathrm{c}})\cdot (1/l_1^2+1/l_2^2)$ selects between the two regimes. For $f_{11}\le f_{\mathrm{c}}/2$ the element is mode dense at its critical frequency and Formula (B.5) applies: $\sigma ={\sigma }_1$ at and above fc, and below it the edge/corner sum $\sigma =2(l_1+l_2)/(l_1{l}_2)\cdot (c_o/f_{\mathrm{c}})\cdot {\delta }_1+{\delta }_2$ with $\lambda =\sqrt{f/f_{\mathrm{c}}}$ and δ2 vanishing above fc/2. For $f_{11}>f_{\mathrm{c}}/2$ Formula (B.6) picks σ3 unless σ2 (below fc) or σ1 (above fc) is smaller. Every branch is capped at $\sigma \le 2.0$.

These relations hold for a plate in an infinite baffle; the standard notes that walls and floors surrounded by orthogonal elements radiate 2 (edge modes) to 4 (corner modes) times more efficiently well below fc.

Parameters

Name	Description
frequencies	Band centre frequencies f, in Hz.
critical_frequency	Critical frequency $f_{\mathrm{c}}=c_o^2/(1.8c_{\mathrm{L}}t)$, Hz.
length1	One side length of the rectangular element, in m.
length2	The other side length, in m.
speed_of_sound	Speed of sound in air co, in m/s (Default: 340 m/s, the value ISO 12354-1 Annex A fixes).

Returns: The radiation factor σ per band (dimensionless).

Raises

Exception	When
ValueError	If any input is not positive and finite.

calculated_sound_reduction_index

calculated_sound_reduction_index(
    frequencies: ArrayLike,
    *,
    mass_per_area: float,
    critical_frequency: float,
    total_loss_factor: ArrayLike,
    radiation_factor: ArrayLike,
    forced_radiation_factor: ArrayLike,
    bands: BandType = 'third',
    resonant_only: bool = False,
    density: float | None = None,
    longitudinal_velocity: float | None = None,
    speed_of_sound: float = 340.0,
    air_density: float = 1.29,
) -> np.ndarray

Sound reduction index of a homogeneous element (Formulae B.2, B.10).

$R=-10{\log }_{10}\tau$ with the three-branch transmission factor

• $f>f_{\mathrm{c}}$: $\tau =(2{\rho }_o{c}_o/(2\pi f{m}^{\prime }){)}^2\cdot \pi f_{\mathrm{c}}{\sigma }^2/(2f{\eta }_{\mathrm{tot}})$,
• $f\approx f_{\mathrm{c}}$: $\tau =(2{\rho }_o{c}_o/(2\pi f{m}^{\prime }){)}^2\cdot \pi {\sigma }^2/(2{\eta }_{\mathrm{tot}})$,
• $f<f_{\mathrm{c}}$: $\tau =(2{\rho }_o{c}_o/(2\pi f{m}^{\prime }){)}^2\cdot (F+R)$ with the forced term $F=2{\sigma }_{\mathrm{f}}[1-f^2/f_{\mathrm{c}}^2{]}^{-2}$ and the resonant term $R=2(\pi f_{\mathrm{c}}/(4f)){\sigma }^2/{\eta }_{\mathrm{tot}}$.

The $f\approx f_{\mathrm{c}}$ branch is applied to the band whose limits straddle the critical frequency, which is how the Annex L worked example selects it.

Below the critical frequency the first term is the forced contribution. Annex B.1 requires flanking paths to use the resonant transmission only; resonant_only=True drops that term (Annex B.3: “the contribution of forced transmission can be neglected for flanking paths”). The Annex L worked example keeps it on every path, so the default is False.

High-frequency plateau (Formula B.10). At high frequency the index of a thick element stops growing; the standard bounds the transmission factor from below by ${\tau }_{\mathrm{plateau}}=(4{\rho }_o{c}_o/(1.1\rho c_{\mathrm{L}}){)}^2\cdot 0.02/{\eta }_{\mathrm{tot}}$. Supplying both density and longitudinal_velocity applies that floor, $\tau =\max (\tau ,{\tau }_{\mathrm{plateau}})$, as the Annex L example does from about 1250 Hz upwards on its lightweight blockwork.

Parameters

Name	Description
frequencies	Band centre frequencies f, in Hz.
mass_per_area	Mass per unit area m', in kg/m².
critical_frequency	Critical frequency fc, in Hz.
total_loss_factor	Total loss factor ηtot per band (laboratory or in situ, matching the situation being described).
radiation_factor	Radiation factor for free bending waves σ per band (see bending_radiation_factor).
forced_radiation_factor	Radiation factor for forced waves σf per band (see forced_radiation_factor); ignored when resonant_only is set.
bands	"third" (default) or "octave", setting the band limits used to locate the $f\approx f_{\mathrm{c}}$ branch.
resonant_only	Drop the forced-transmission term below fc.
density	Density ρ of the material, in kg/m³; with longitudinal_velocity it enables the Formula (B.10) plateau.
longitudinal_velocity	Quasi-longitudinal phase velocity cL of the material, in m/s.
speed_of_sound	Speed of sound in air co, in m/s.
air_density	Density of air ρo, in kg/m³.

Returns: The sound reduction index R per band, in dB.

Raises

Exception	When
ValueError	If an input is not positive/finite or the per-band arrays do not share the band count.

detailed_airborne_prediction

detailed_airborne_prediction(
    frequencies: ArrayLike,
    *,
    direct_index: ArrayLike,
    flanking_paths: Sequence[BandPath] = (),
    direct_label: str = 'Dd',
    bands: BandType = 'third',
) -> DetailedAirborneResult

Combine direct and flanking paths into R' per band (F. 1 to 4).

$R^{\prime }=-10{\log }_{10}(\sum 10^{-R/10})$ over the direct path RDd and every flanking path Rij. The result exposes each path’s share of the transmitted energy in every band, which is what identifies the path to treat first, and the ISO 717-1 rating of the resulting spectrum whenever the bands cover the rating range (100 Hz to 3150 Hz in one-third octaves, 125 Hz to 2000 Hz in octaves).

Parameters

Name	Description
frequencies	Band centre frequencies, in Hz.
direct_index	RDd per band, in dB (see direct_reduction_index).
flanking_paths	The flanking paths (see airborne_flanking_path); may be empty.
direct_label	Label of the direct path (Default: "Dd").
bands	"third" (default) or "octave", selecting the ISO 717-1 rating range.

Returns: The DetailedAirborneResult.

Raises

Exception	When
ValueError	If a path does not match the band count.

detailed_impact_prediction

detailed_impact_prediction(
    frequencies: ArrayLike,
    *,
    direct_level: ArrayLike | None = None,
    flanking_paths: Sequence[BandPath] = (),
    direct_label: str = 'Dd',
    bands: BandType = 'third',
) -> DetailedImpactResult

Combine direct and flanking paths into L'n per band (Part 2, (1)).

$L_{\mathrm{n}}^{\prime }=10{\log }_{10}(\sum 10^{L_{\mathrm{n}}/10})$ over the direct impact path Ln,d and every flanking path Ln,ij, with the ISO 717-2 rating of the resulting spectrum whenever the bands cover the rating range. For rooms next to each other there is no direct impact path and the sum runs over the flanking paths only (Part 2, Formula 2): leave direct_level out and the result carries no direct path at all.

Parameters

Name	Description
frequencies	Band centre frequencies, in Hz.
direct_level	Ln,d per band, in dB (see direct_impact_level), or None for the Formula (2) case of two rooms next to each other, which has no direct path.
flanking_paths	The flanking paths (see impact_flanking_path); may be empty when direct_level is given.
direct_label	Label of the direct path (Default: "Dd").
bands	"third" (default) or "octave".

Returns: The DetailedImpactResult.

Raises

Exception	When
ValueError	If a path does not match the band count, or if neither a direct level nor any flanking path is given.

DetailedAirborneResult

DetailedAirborneResult(
    frequencies: np.ndarray,
    paths: tuple[BandPath, ...],
    r_prime: np.ndarray,
    fractions: np.ndarray,
    rating: WeightedRatingResult | None,
)

Per-band apparent sound reduction index R' (ISO 12354-1, 4.2).

Attributes

Name	Description
frequencies	Band centre frequencies, in Hz.
paths	Every transmission path (the direct path first), each with its Rij per band.
r_prime	Apparent sound reduction index R' per band, in dB.
fractions	Share of the transmitted energy carried by each path per band (paths x bands), summing to 1 in every band.
rating	R'w (C; Ctr) per ISO 717-1, or None when the bands supplied do not cover the rating range.

DetailedAirborneResult.dominant

property

Label of the path carrying most energy in each band.

DetailedAirborneResult.plot()

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

Plot the per-band path contributions and the resulting R'.

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

DetailedAirborneResult.report()

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

Render a detailed airborne prediction fiche (EN/ISO 12354-1).

Writes a one-page prediction report for the per-band detailed model: a basis line naming ISO 12354-1:2017 Clause 4.2, an optional metadata header, a two-panel body with the per-path energy-share table beside the per-band path-contribution figure, the boxed predicted R'w, the prediction statement and, when a requirement is supplied, a PASS/FAIL verdict, followed by the footer.

Parameters

Name	Description
path	Destination path of the PDF file.
metadata	Optional ReportMetadata.
engine	Rendering back end; only "reportlab" is supported.
verbose	When True the path table also gives the band in which each path contributes most.
language	"en" (default) or "es".

Returns: The written path as a str.

Raises

Exception	When
ValueError	If engine/language is unknown or the result carries no ISO 717-1 rating.
ImportError	If reportlab or matplotlib is missing.

DetailedImpactResult

DetailedImpactResult(
    frequencies: np.ndarray,
    paths: tuple[BandPath, ...],
    l_prime_n: np.ndarray,
    fractions: np.ndarray,
    rating: ImpactRatingResult | None,
)

Per-band apparent impact level L'n (ISO 12354-2, 4.2).

Attributes

Name	Description
frequencies	Band centre frequencies, in Hz.
paths	Every transmission path (the direct path first), each with its Ln,ij per band.
l_prime_n	Apparent normalized impact level L'n per band, in dB.
fractions	Share of the radiated energy carried by each path per band (paths x bands), summing to 1 in every band.
rating	L'n,w (CI) per ISO 717-2, or None when the bands supplied do not cover the rating range.

DetailedImpactResult.dominant

property

Label of the path carrying most energy in each band.

DetailedImpactResult.plot()

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

Plot the per-band path contributions and the resulting L'n.

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

DetailedImpactResult.report()

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

Render a detailed impact prediction fiche (EN/ISO 12354-2).

The impact counterpart of DetailedAirborneResult.report: the per-band detailed model of ISO 12354-2:2017 Clause 4.2, with the boxed predicted L'n,w and a PASS/FAIL verdict against a requirement (a lower level passing).

Parameters

Name	Description
path	Destination path of the PDF file.
metadata	Optional ReportMetadata.
engine	Rendering back end; only "reportlab" is supported.
verbose	When True the path table also gives the band in which each path contributes most.
language	"en" (default) or "es".

Returns: The written path as a str.

Raises

Exception	When
ValueError	If engine/language is unknown or the result carries no ISO 717-2 rating.
ImportError	If reportlab or matplotlib is missing.

direct_impact_level

direct_impact_level(
    floor_level: ArrayLike,
    *,
    delta_l: ArrayLike = 0.0,
    delta_l_ceiling: ArrayLike = 0.0,
) -> np.ndarray

Normalized impact level of the direct path Ln,d (Part 2, F. 11).

$L_{\mathrm{n},\mathrm{d}}=L_{\mathrm{n},\mathrm{situ}}-\Delta L_{\mathrm{situ}}-\Delta L_{\mathrm{d},\mathrm{situ}}$: the in-situ level of the bare floor reduced by the floor covering and by any additional layer on the receiving side (a suspended ceiling).

Parameters

Name	Description
floor_level	Ln,situ of the bare separating floor, per band, dB.
delta_l	Improvement of the floor covering ΔLsitu, per band, dB.
delta_l_ceiling	Improvement ΔLd,situ of a layer on the receiving side, per band, in dB.

Returns: Ln,d per band, in dB.

direct_reduction_index

direct_reduction_index(
    separating_index: ArrayLike,
    *,
    delta_r_source: ArrayLike = 0.0,
    delta_r_receiving: ArrayLike = 0.0,
) -> np.ndarray

Sound reduction index of the direct path RDd (Formula 14).

$R_{\mathrm{Dd}}=R_{\mathrm{s},\mathrm{situ}}+\Delta R_{\mathrm{D},\mathrm{situ}}+\Delta R_{\mathrm{d},\mathrm{situ}}$: the in-situ index of the separating element plus the improvement of any lining on its source and receiving faces (for the in-situ improvement the standard accepts the laboratory value, Formula 8).

Parameters

Name	Description
separating_index	Rs,situ per band, in dB.
delta_r_source	ΔRD,situ on the source side, per band, in dB.
delta_r_receiving	ΔRd,situ on the receiving side, in dB.

Returns: RDd per band, in dB.

flanking_impact_level

flanking_impact_level(
    *,
    floor_level: ArrayLike,
    index_i: ArrayLike,
    index_j: ArrayLike,
    velocity_level_difference: ArrayLike,
    area_i: float,
    area_j: float,
    delta_l: ArrayLike = 0.0,
    delta_r_j: ArrayLike = 0.0,
) -> np.ndarray

Flanking normalized impact level Ln,ij per band (Part 2, F. 12).

$L_{\mathrm{n},ij}=L_{\mathrm{n},\mathrm{situ}}-\Delta L_{\mathrm{situ}}+(R_{i,\mathrm{situ}}-R_{j,\mathrm{situ}})/2-\Delta R_{j,\mathrm{situ}}-D_{v,ij,\mathrm{situ}}-T$ with the geometry term $T=10{\log }_{10}(S_i/\sqrt{S_i{S}_j})$, i the excited floor and j the flanking element radiating in the receiving room.

Parameters

Name	Description
floor_level	Ln,situ of the excited floor, per band, in dB.
index_i	Ri,situ of the excited floor, per band, in dB.
index_j	Rj,situ of the flanking element, per band, in dB.
velocity_level_difference	Dv,ij,situ per band, in dB.
area_i	Area Si of the excited floor, in m².
area_j	Area Sj of the flanking element, in m².
delta_l	Improvement of the floor covering ΔLsitu, in dB.
delta_r_j	Improvement ΔRj,situ of a lining on the flanking element, per band, in dB.

Returns: Ln,ij per band, in dB.

Raises

Exception	When
ValueError	If an area is not positive and finite.

flanking_impact_level_from_flanking_level

flanking_impact_level_from_flanking_level(
    normalized_flanking_impact_level: ArrayLike,
    *,
    area: float,
    laboratory_area: float,
    coupling_length: float,
    laboratory_coupling_length: float,
) -> np.ndarray

Flanking impact level from a measured Ln,f (Part 2, Formula 13).

$L_{\mathrm{n},ij}=L_{\mathrm{n},\mathrm{f},ij,\mathrm{situ}}-10{\log }_{10}(S_i{l}_{\mathrm{lab}}/(S_{i,\mathrm{lab}}{l}_{ij}))$, the impact twin of the airborne flanking_reduction_index_from_flanking_level: the route used when the flanking construction is characterised as a whole by a laboratory measurement of the normalized flanking impact sound pressure level (ISO 10848) instead of by the properties of its elements. The laboratory measurement is transferred to the field situation first, as ISO 12354-2:2017, Annex D indicates.

Parameters

Name	Description
normalized_flanking_impact_level	Ln,f,ij,situ per band, in dB.
area	In-situ area Si of the excited floor, in m².
laboratory_area	Laboratory area Si,lab of the excited floor, in m².
coupling_length	In-situ coupling length lij, in m.
laboratory_coupling_length	Laboratory coupling length llab, in m. ISO 12354-1 Clause 4.4.2 gives the usual values: 4,5 m for horizontal flanking elements, 2,5 m for vertical ones.

Returns: Ln,ij per band, in dB.

Raises

Exception	When
ValueError	If a geometry value is not positive and finite.

flanking_impact_level_from_normalized_difference

flanking_impact_level_from_normalized_difference(
    *,
    floor_level: ArrayLike,
    index_i: ArrayLike,
    index_j: ArrayLike,
    normalized_velocity_level_difference: ArrayLike,
    area_i: float,
    coupling_length: float,
    delta_l: ArrayLike = 0.0,
    delta_r_j: ArrayLike = 0.0,
) -> np.ndarray

Flanking impact level of a Type B junction (Part 2, Formula 14).

$L_{\mathrm{n},ij}=L_{\mathrm{n},ii}-\Delta L_i+(R_i-R_j)/2-\Delta R_j-D_{v,ij,\mathrm{n}}-10{\log }_{10}(S_i/(l_o{l}_{ij}))$ with the reference length $l_o=1$ m: Formula (12) with the junction described by the normalized direction-averaged velocity level difference instead of Kij, the form used for lightweight constructions.

Parameters

Name	Description
floor_level	Ln,ii of the excited bare floor, per band, in dB.
index_i	Ri of the excited floor, per band, in dB.
index_j	Rj of the flanking element, per band, in dB.
normalized_velocity_level_difference	Dv,ij,n per band, in dB.
area_i	Area Si of the excited floor, in m².
coupling_length	Common coupling length lij, in m.
delta_l	Improvement of the floor covering ΔLi, per band, dB.
delta_r_j	Improvement ΔRj of a lining on the flanking element, per band, in dB.

Returns: Ln,ij per band, in dB.

Raises

Exception	When
ValueError	If a geometry value is not positive and finite.

flanking_reduction_index

flanking_reduction_index(
    *,
    index_i: ArrayLike,
    index_j: ArrayLike,
    velocity_level_difference: ArrayLike,
    separating_area: float,
    area_i: float,
    area_j: float,
    delta_r_i: ArrayLike = 0.0,
    delta_r_j: ArrayLike = 0.0,
) -> np.ndarray

Flanking sound reduction index Rij per band (Formula 15).

$R_{ij}=R_{i,\mathrm{situ}}/2+\Delta R_{i,\mathrm{situ}}+R_{j,\mathrm{situ}}/2+\Delta R_{j,\mathrm{situ}}+D_{v,ij,\mathrm{situ}}+T$ for ij = Ff, Fd, Df, with the geometry term $T=10{\log }_{10}(S_{\mathrm{s}}/\sqrt{S_i{S}_j})$. For diagonal transmission the standard fixes $S_{\mathrm{s}}=10$ m².

The element indices depend on the path: Ff takes the flanking element on both sides, Fd the flanking element as i and the separating element as j, and Df the separating element as i and the flanking element as j.

Parameters

Name	Description
index_i	Ri,situ of the element excited in the source room, in dB per band.
index_j	Rj,situ of the radiating element in the receiving room, per band, in dB.
velocity_level_difference	Dv,ij,situ per band, in dB (see in_situ_velocity_level_difference; for a Type B junction pass the Formula (12) value derived from Dv,ij,n).
separating_area	Separating-element area Ss, in m².
area_i	Area Si of element i, in m².
area_j	Area Sj of element j, in m².
delta_r_i	ΔRi,situ on element i, per band, in dB.
delta_r_j	ΔRj,situ on element j, per band, in dB.

Returns: Rij per band, in dB.

Raises

Exception	When
ValueError	If an area is not positive and finite.

flanking_reduction_index_from_flanking_level

flanking_reduction_index_from_flanking_level(
    flanking_level_difference: ArrayLike,
    *,
    separating_area: float,
    coupling_length: float,
    laboratory_coupling_length: float,
    reference_absorption_area: float = 10.0,
) -> np.ndarray

Flanking index from a measured Dn,f (Formula 16).

$R_{ij}=D_{\mathrm{n},\mathrm{f},ij,\mathrm{situ}}+10{\log }_{10}(S_{\mathrm{s}}{l}_{\mathrm{lab}}/(A_o{l}_{ij}))$ with $A_o=10$ m², the route used when the flanking construction is characterised as a whole by a laboratory measurement of the flanking normalized level difference (ISO 10848). ISO 12354-1 Clause 4.4.2 gives the usual laboratory coupling lengths: 4,5 m for horizontal flanking elements such as ceilings, 2,5 m for vertical ones such as facades.

Parameters

Name	Description
flanking_level_difference	Dn,f,ij,situ per band, in dB.
separating_area	Separating-element area Ss, in m².
coupling_length	In-situ coupling length lij, in m.
laboratory_coupling_length	Laboratory coupling length llab, m.
reference_absorption_area	Ao, in m² (Default: 10 m²).

Returns: Rij per band, in dB.

Raises

Exception	When
ValueError	If a geometry value is not positive and finite.

flanking_reduction_index_from_normalized_difference

flanking_reduction_index_from_normalized_difference(
    *,
    index_i: ArrayLike,
    index_j: ArrayLike,
    normalized_velocity_level_difference: ArrayLike,
    separating_area: float,
    coupling_length: float,
    delta_r_i: ArrayLike = 0.0,
    delta_r_j: ArrayLike = 0.0,
) -> np.ndarray

Flanking index of a Type B junction Rij (Formula 17).

$R_{ij}=R_{i,\mathrm{situ}}/2+\Delta R_{i,\mathrm{situ}}+R_{j,\mathrm{situ}}/2+\Delta R_{j,\mathrm{situ}}+D_{v,ij,\mathrm{n}}+T$ with the geometry term $T=10{\log }_{10}(S_{\mathrm{s}}/(l_o{l}_{ij}))$ and the reference length $l_o=1$ m. It is Formula (15) with Formula (12) substituted, so the junction is described by the normalized direction-averaged velocity level difference Dv,ij,n (ISO 12354-1 Annex F) rather than by Kij: the form used for lightweight double-leaf constructions, where the indices refer either to the double element as a whole or to its inner leaf and should relate to resonant transmission only (see resonant_sound_reduction_index).

Parameters

Name	Description
index_i	Ri,situ of the element excited in the source room, in dB per band.
index_j	Rj,situ of the radiating element, per band, in dB.
normalized_velocity_level_difference	Dv,ij,n per band, in dB.
separating_area	Separating-element area Ss, in m².
coupling_length	Common coupling length lij, in m.
delta_r_i	ΔRi,situ on element i, per band, in dB.
delta_r_j	ΔRj,situ on element j, per band, in dB.

Returns: Rij per band, in dB.

Raises

Exception	When
ValueError	If a geometry value is not positive and finite.

floating_floor_improvement

floating_floor_improvement(
    frequencies: ArrayLike,
    *,
    resonance_frequency: float,
    slope: float = 30.0,
) -> np.ndarray

Improvement of a floating floor ΔL per band (Part 2, Formula C.1).

$\Delta L=30{\log }_{10}(f/f_o)$ for sand/cement or calcium-sulfate screeds and $\Delta L=40{\log }_{10}(f/f_o)$ (slope=40, Formula C.3) for asphalt or dry floating floors, with the system resonance $f_o=160\sqrt{s^{\prime }/m^{\prime }}$ (Formula C.2) and no improvement at or below it. The Annex L airborne example reuses the same curve as ΔR, noting explicitly that assuming $\Delta R=\Delta L$ is rough.

Parameters

Name	Description
frequencies	Band centre frequencies f, in Hz.
resonance_frequency	Resonance frequency fo, in Hz.
slope	30 (screed, Formula C.1) or 40 (asphalt/dry, Formula C.3).

Returns: The improvement ΔL per band, in dB (0 at and below fo).

Raises

Exception	When
ValueError	If an input is not positive and finite.

forced_radiation_factor

forced_radiation_factor(
    frequencies: ArrayLike,
    *,
    length1: float,
    length2: float,
    speed_of_sound: float = 340.0,
) -> np.ndarray

Radiation factor for forced waves σf (Formula B.3).

${\sigma }_{\mathrm{f}}=0.5(\ln (k_o\sqrt{l_1{l}_2})-\Lambda )$ capped at ${\sigma }_{\mathrm{f}}\le 2$, with $k_o=2\pi f/c_o$ and, for $l_1>l_2$,

$$\Lambda =-0.964-\left(0.5+\frac{l_2}{\pi l_1}\right)\ln \frac{l_2}{l_1}+\frac{5l_2}{2\pi l_1}-E$$

with $E=1/(4\pi l_1{l}_2{k}_o^2)$.

ISO 12354-1:2017 Table B.1 tabulates $10{\log }_{10}{\sigma }_{\mathrm{f}}$ for the two standard laboratory openings (2 m² and 10 m²), which this implementation reproduces.

Parameters

Name	Description
frequencies	Band centre frequencies f, in Hz.
length1	One side length of the rectangular element, in m.
length2	The other side length, in m.
speed_of_sound	Speed of sound in air co, in m/s (Default: 340 m/s).

Returns: The forced radiation factor σf per band (dimensionless), clipped to $0\le {\sigma }_{\mathrm{f}}\le 2$ (the standard prints only the upper bound; the lower one guards the deep low-frequency extrapolation, where the logarithm turns negative).

Raises

Exception	When
ValueError	If any input is not positive and finite.

HomogeneousElement

HomogeneousElement(
    label: str,
    area: float,
    length1: float,
    length2: float,
    mass_per_area: float,
    critical_frequency: float,
    internal_loss_factor: float = 0.01,
    perimeter_absorption: float = 0.0,
    density: float | None = None,
    longitudinal_velocity: float | None = None,
)

A Type A homogeneous element of the detailed model.

Attributes

Name	Description
label	Human-readable element name, e.g. "separating floor".
area	Element area S, in m².
length1	One side length of the rectangular element, in m.
length2	The other side length, in m.
mass_per_area	Mass per unit area m', in kg/m².
critical_frequency	Critical frequency fc, in Hz.
internal_loss_factor	Internal loss factor ηint of the material (about 0,01 for common homogeneous building materials; ISO 12354-1 Table B.3 tabulates it per material).
perimeter_absorption	$\sum l_k{\alpha }_k$ over the element’s perimeter, in m (Formula C.1; build it from perimeter_absorption_coefficient times the border lengths).
density	Density ρ of the material, in kg/m³; supplied together with longitudinal_velocity it enables the high-frequency plateau of Formula (B.10). None (the default) leaves the plateau off.
longitudinal_velocity	Quasi-longitudinal phase velocity cL of the material, in m/s (ISO 12354-1 Table B.3).

impact_flanking_path

impact_flanking_path(
    *,
    label: str,
    floor: InSituElementResult,
    element_j: InSituElementResult,
    vibration_reduction_index: ArrayLike,
    coupling_length: float,
    delta_l: ArrayLike = 0.0,
    delta_r_j: ArrayLike = 0.0,
) -> BandPath

Build one impact flanking path Df (Part 2, Formula 12).

Parameters

Name	Description
label	Human-readable path name.
floor	The excited separating floor, in situ.
element_j	The flanking element radiating in the receiving room.
vibration_reduction_index	Kij of this path, in dB.
coupling_length	Common coupling length lij, in m.
delta_l	Improvement of the floor covering ΔLsitu, in dB.
delta_r_j	ΔRj,situ of a lining on the flanking element, in dB.

Returns: The BandPath carrying Ln,ij.

Raises

Exception	When
ValueError	If a geometry value is not positive and finite.

in_situ_element

in_situ_element(
    element: HomogeneousElement,
    frequencies: ArrayLike,
    *,
    bands: BandType = 'third',
    resonant_only: bool = False,
    speed_of_sound: float = 340.0,
    air_density: float = 1.29,
) -> InSituElementResult

Evaluate one homogeneous element in situ, per band (Clause 4.2.2).

Runs the whole Annex B / Annex C chain in one call: the two radiation factors, the in-situ total loss factor and structural reverberation time, the equivalent absorption length, the calculated in-situ sound reduction index and, for a floor, the calculated in-situ normalized impact level.

Because the element performance is calculated from material properties, the in-situ loss factor enters Formula (B.2) directly and no $10{\log }_{10}(T_{\mathrm{s},\mathrm{situ}}/T_{\mathrm{s},\mathrm{lab}})$ transfer is needed (Annex B.3). Use in_situ_reduction_index instead when the element data come from a laboratory measurement.

Parameters

Name	Description
element	The HomogeneousElement description.
frequencies	Band centre frequencies, in Hz.
bands	"third" (default) or "octave".
resonant_only	Drop the forced-transmission term of Formula (B.2) below fc (Annex B.1, flanking paths).
speed_of_sound	Speed of sound in air co, in m/s.
air_density	Density of air ρo, in kg/m³.

Returns: The InSituElementResult.

Raises

Exception	When
ValueError	If any element property is not positive and finite.

in_situ_equivalent_absorption_length

in_situ_equivalent_absorption_length(
    frequencies: ArrayLike,
    *,
    area: float,
    situ_reverberation_time: ArrayLike,
    speed_of_sound: float = 340.0,
) -> np.ndarray

In-situ equivalent absorption length asitu (Formula 11).

$a_{\mathrm{situ}}=2.2{\pi }^{2}S\sqrt{f_{\mathrm{ref}}/f}/(c_o{T}_{\mathrm{s},\mathrm{situ}})$ with $f_{\mathrm{ref}}=1000$ Hz. Note the $\sqrt{f_{\mathrm{ref}}/f}$ dependence: the absorption length grows as the element rings shorter at high frequency. For a Type B element the standard replaces it by the element area, $a_{\mathrm{situ}}=S/l_o$ (Formula 13).

This is the ISO 10848 Formula (12) quantity (phonometry.equivalent_absorption_length) evaluated with the ISO 12354 value $c_o=340$ m/s.

Parameters

Name	Description
frequencies	Band centre frequencies f, in Hz.
area	Element area S, in m².
situ_reverberation_time	Ts,situ per band, in s.
speed_of_sound	Speed of sound in air co, in m/s.

Returns: The equivalent absorption length asitu per band, in m.

Raises

Exception	When
ValueError	If an input is not positive/finite or the band counts disagree.

in_situ_impact_level

in_situ_impact_level(
    impact_level: ArrayLike,
    situ_reverberation_time: ArrayLike,
    laboratory_reverberation_time: ArrayLike,
) -> np.ndarray

In-situ normalized impact level Ln,situ (Part 2, Formula 5).

$L_{\mathrm{n},\mathrm{situ}}=L_{\mathrm{n}}+10{\log }_{10}(T_{\mathrm{s},\mathrm{situ}}/T_{\mathrm{s},\mathrm{lab}})$, the sign opposite to in_situ_reduction_index: a floor that rings longer in the building than in the laboratory radiates more impact sound.

Parameters

Name	Description
impact_level	Laboratory level Ln per band, in dB.
situ_reverberation_time	Ts,situ per band, in s.
laboratory_reverberation_time	Ts,lab per band, in s.

Returns: The in-situ level Ln,situ per band, in dB.

Raises

Exception	When
ValueError	If a reverberation time is not positive/finite or the band counts disagree.

in_situ_reduction_index

in_situ_reduction_index(
    sound_reduction_index: ArrayLike,
    situ_reverberation_time: ArrayLike,
    laboratory_reverberation_time: ArrayLike,
) -> np.ndarray

In-situ sound reduction index Rsitu (Formula 9).

$R_{\mathrm{situ}}=R-10{\log }_{10}(T_{\mathrm{s},\mathrm{situ}}/T_{\mathrm{s},\mathrm{lab}})$: an element that is better damped in the building than in the test frame radiates less and gains index. The standard notes that $R_{\mathrm{situ}}=R$ is a usable first approximation, and the correction is exactly zero for Type B elements (Clause 4.2.2.3).

Parameters

Name	Description
sound_reduction_index	Laboratory index R per band, in dB.
situ_reverberation_time	In-situ structural reverberation time Ts,situ per band, in s.
laboratory_reverberation_time	Laboratory structural reverberation time Ts,lab per band, in s.

Returns: The in-situ index Rsitu per band, in dB.

Raises

Exception	When
ValueError	If a reverberation time is not positive/finite or the band counts disagree.

in_situ_total_loss_factor

in_situ_total_loss_factor(
    frequencies: ArrayLike,
    *,
    internal_loss_factor: float,
    mass_per_area: float,
    area: float,
    critical_frequency: float,
    radiation_factor: ArrayLike,
    perimeter_absorption: float,
    speed_of_sound: float = 340.0,
    air_density: float = 1.29,
) -> np.ndarray

Total loss factor in situ ηtot,situ (Formula C.1).

${\eta }_{\mathrm{tot}}={\eta }_{\mathrm{int}}+2{\rho }_o{c}_o\sigma /(2\pi f{m}^{\prime })+c_o/({\pi }^{2}S\sqrt{f{f}_{\mathrm{c}}})\cdot {\sum }_k{l}_k{\alpha }_k$: the internal losses of the material, the losses by radiation into the air and the losses at the perimeter of the element. $\sum l_k{\alpha }_k$ is the junction-length-weighted sum of the Formula (C.4) absorption coefficients (see perimeter_absorption_coefficient).

Parameters

Name	Description
frequencies	Band centre frequencies f, in Hz.
internal_loss_factor	Internal loss factor ηint of the material (about 0,01 for common homogeneous building materials).
mass_per_area	Mass per unit area m', in kg/m².
area	Element area S, in m².
critical_frequency	Critical frequency fc, in Hz.
radiation_factor	Radiation factor σ per band.
perimeter_absorption	$\sum l_k{\alpha }_k$ over the element’s perimeter, in m (may be zero for a free-edged element).
speed_of_sound	Speed of sound in air co, in m/s.
air_density	Density of air ρo, in kg/m³.

Returns: The total loss factor ηtot,situ per band (dimensionless).

Raises

Exception	When
ValueError	If an input is not positive/finite, the perimeter sum is negative, or the band counts disagree.

in_situ_velocity_level_difference

in_situ_velocity_level_difference(
    vibration_reduction_index: ArrayLike,
    *,
    coupling_length: float,
    absorption_length_i: ArrayLike,
    absorption_length_j: ArrayLike,
) -> np.ndarray

In-situ velocity level difference Dv,ij,situ (Formula 10).

$D_{v,ij,\mathrm{situ}}=K_{ij}-10{\log }_{10}(l_{ij}/\sqrt{a_{i,\mathrm{situ}}{a}_{j,\mathrm{situ}}})$, floored at 0 dB as the formula prescribes. It converts the situation-invariant junction descriptor Kij (ISO 12354-1 Annex E, or measured per ISO 10848) into the level drop the junction actually produces between the two elements as built.

Parameters

Name	Description
vibration_reduction_index	Kij per band (or a single value broadcast to all bands), in dB.
coupling_length	Common coupling length lij, in m.
absorption_length_i	ai,situ per band, in m.
absorption_length_j	aj,situ per band, in m.

Returns: Dv,ij,situ per band, in dB (never negative).

Raises

Exception	When
ValueError	If a length is not positive/finite or the band counts disagree.

InSituElementResult

InSituElementResult(
    label: str,
    frequencies: np.ndarray,
    area: float,
    radiation_factor: np.ndarray,
    forced_radiation_factor: np.ndarray,
    total_loss_factor: np.ndarray,
    reverberation_time: np.ndarray,
    absorption_length: np.ndarray,
    sound_reduction_index: np.ndarray,
    impact_level: np.ndarray,
)

Per-band in-situ description of one element (Clause 4.2.2).

Attributes

Name	Description
label	The element name.
frequencies	Band centre frequencies, in Hz.
area	Element area S, in m².
radiation_factor	Radiation factor for free bending waves σ.
forced_radiation_factor	Radiation factor for forced waves σf.
total_loss_factor	In-situ total loss factor ηtot,situ.
reverberation_time	In-situ structural reverberation time Ts,situ, in s.
absorption_length	In-situ equivalent absorption length asitu, in m.
sound_reduction_index	In-situ sound reduction index Rsitu, dB.
impact_level	In-situ normalized impact level Ln,situ of the bare element, in dB (meaningful for the excited floor).

InSituElementResult.plot()

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

Plot the in-situ Rsitu and Ln,situ spectra of the element.

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

laboratory_total_loss_factor

laboratory_total_loss_factor(
    frequencies: ArrayLike,
    *,
    mass_per_area: float,
    internal_loss_factor: float = 0.01,
) -> np.ndarray

Total loss factor in the laboratory ηtot,lab (Formula C.3).

${\eta }_{\mathrm{tot},\mathrm{lab}}\approx {\eta }_{\mathrm{int}}+m^{\prime }/(485\sqrt{f})$, the estimate for the heavy test frame of an ISO 10140 facility. The relation holds for elements below $m^{\prime }=800$ kg/m² and ηint can normally be taken as 0.01.

Parameters

Name	Description
frequencies	Band centre frequencies f, in Hz.
mass_per_area	Mass per unit area m', in kg/m².
internal_loss_factor	Internal loss factor ηint (Default: 0,01).

Returns: The laboratory total loss factor per band (dimensionless).

Raises

Exception	When
ValueError	If an input is not positive and finite.

perimeter_absorption_coefficient

perimeter_absorption_coefficient(
    critical_frequencies: ArrayLike,
    vibration_reduction_indices: ArrayLike,
) -> float

Absorption coefficient for bending waves at one border (Formula C.4).

${\alpha }_k={\sum }_j\sqrt{f_{\mathrm{c},j}/f_{\mathrm{ref}}}\cdot 10^{-K_{ij}/10}$ summed over the elements j connected to the considered element at border k (the standard sums over at most three). Multiplied by the border length and summed over the perimeter it gives the $\sum l_k{\alpha }_k$ that in_situ_total_loss_factor takes. Annex C.3 places the in-situ coefficients between 0,05 and 0,5.

Parameters

Name	Description
critical_frequencies	Critical frequency fc,j of each connected element, in Hz.
vibration_reduction_indices	Vibration reduction index Kij of the path to each connected element, in dB (same order and length).

Returns: The absorption coefficient αk at that border (dimensionless).

Raises

Exception	When
ValueError	If the two sequences differ in length, a critical frequency is not positive, or an index is not finite.

reciprocity_impact_level

reciprocity_impact_level(
    sound_reduction_index: ArrayLike,
    frequencies: ArrayLike,
    *,
    bands: BandType = 'third',
) -> np.ndarray

Impact level of a homogeneous floor by reciprocity (Part 2, B.3/B.4).

$R+L_{\mathrm{n}}=38+30{\log }_{10}(f/1\mathrm{Hz})$ in one-third-octave bands and $R+L_{\mathrm{n}}=43+30{\log }_{10}(f/1\mathrm{Hz})$ in octave bands: for a homogeneous floor the sum of the airborne index and the normalized impact level depends only on frequency, provided forced transmission is negligible (normally up to about 1 kHz, above which the stiffness of the floor’s top layer matters).

Parameters

Name	Description
sound_reduction_index	R of the floor per band, in dB.
frequencies	Band centre frequencies, in Hz.
bands	"third" (default, constant 38) or "octave" (43).

Returns: The normalized impact sound pressure level Ln per band, dB.

Raises

Exception	When
ValueError	If an input is not positive/finite or the band counts disagree.

resonant_sound_reduction_index

resonant_sound_reduction_index(
    sound_reduction_index: ArrayLike,
    frequencies: ArrayLike,
    *,
    critical_frequency: float,
    correction: float = 8.0,
) -> np.ndarray

Correct a measured R to resonant transmission only (Formula B.1).

$R^{\ast }=R+10{\log }_{10}({\sigma }_{\mathrm{a}}/{\sigma }_{\mathrm{s}})$. No standardized method exists to measure the two radiation factors, so Annex B.2 gives the estimate this function applies: no correction for elements separated by one or two cavities, and a fixed correction (8 dB, the standard’s figure for single homogeneous or layered wood or steel frame elements without a cavity) below the critical frequency only. Above fc the laboratory index already describes resonant transmission and is returned unchanged.

Parameters

Name	Description
sound_reduction_index	Measured index R per band, in dB.
frequencies	Band centre frequencies, in Hz.
critical_frequency	Critical frequency fc, in Hz.
correction	Correction applied below fc, in dB (Default: 8 dB; Annex B.2 caps the estimate of Formula (B.8) at this value, and the Annex L lightweight example reduces it around the cavity resonance).

Returns: The resonant-only index R* per band, in dB.

Raises

Exception	When
ValueError	If an input is not positive/finite or the band counts disagree.

structural_reverberation_time

structural_reverberation_time(
    frequencies: ArrayLike,
    total_loss_factor: ArrayLike,
) -> np.ndarray

Structural reverberation time $T_{\mathrm{s}}=2.2/(f{\eta }_{\mathrm{tot}})$ (C.1).

Parameters

Name	Description
frequencies	Band centre frequencies f, in Hz.
total_loss_factor	Total loss factor ηtot per band.

Returns: The structural reverberation time Ts per band, in s.

Raises

Exception	When
ValueError	If an input is not positive/finite or the band counts disagree.