Source: https://jmrplens.github.io/phonometry/devices/emission/sound-power-pressure/ # Sound Power by Pressure Methods (ISO 3744 / ISO 3746 / ISO 3745) Of the standardised routes to the sound power level $L_W$, the pressure methods are the ones that need nothing more exotic than a sound level meter: sample the sound pressure on a surface that envelops the source, energy-average it, correct it, and add the surface term. This guide covers the three of them. The **enveloping-surface** methods of ISO 3744 (engineering grade) and ISO 3746 (survey grade) work in situ, over one or more reflecting planes, and clean the surface level with the background-noise correction $K_1$ and the environmental correction $K_2$. The **precision method** of ISO 3745 moves the same idea into a qualified anechoic or hemi-anechoic room, where a fixed microphone array samples the free field directly and the grade-1 corrections are meteorological rather than environmental. The closing section renders the determination as the accredited-style test fiche. Which route fits which job, and the reverberation-room and intensity alternatives, are weighed in [Sound Power](https://jmrplens.github.io/phonometry/devices/emission/sound-power/). ## 1. Enveloping surface, sound pressure (ISO 3744 / ISO 3746) Place the source on a reflecting plane and imagine a **measurement surface** of area $S$ wrapping it: a hemisphere for a compact source, a box (right parallelepiped) for a large or elongated one. Sample the sound pressure level at an array of microphone positions on that surface, energy-average them, and the sound power follows because a diffuse-enough surface captures all the radiated energy: $$ \bar{L}_p = 10\log_{10}\left( \frac{1}{N_\mathrm{M}} \sum_i 10^{L_{pi}/10} \right), \qquad L_W = \bar{L}_p - K_1 - K_2 + 10\log_{10}\frac{S}{S_0},\quad S_0 = 1\ \text{m}^2 . $$ Two corrections clean up the surface level. The **background-noise correction** removes the energy that would have been there with the source switched off, from the margin $\Delta L_p$ between source-on and background levels, $$ K_1 = -10\log_{10}\left( 1 - 10^{-\Delta L_p/10} \right), $$ and the **environmental correction** removes the reverberant build-up of the test room from its equivalent absorption area $A$, $$ K_2 = 10\log_{10}\left( 1 + \frac{4 S}{A} \right). $$ The surface area is a closed form of the geometry: a hemisphere is $S = 2\pi r^2$ over one reflecting plane (halved and quartered for two and three planes), and a one-plane box is $S = 4(ab + bc + ca)$ with $a = 0.5\,l_1 + d$, $b = 0.5\,l_2 + d$, $c = l_3 + d$ for measurement distance $d$. ISO 3746 (survey) shares every formula but is coarser: fewer microphone positions, a 3 dB background criterion instead of 6 dB, and validity up to $K_2 \le 7\ \text{dB}$ instead of 4 dB. ```python import numpy as np from phonometry import emission # Octave-band SPL (dB) at the 10 hemisphere positions of ISO 3744 (Annex B), # with the source running, plus the background spectrum with it switched off. freqs = np.array([63, 125, 250, 500, 1000, 2000, 4000, 8000]) base = np.array([70.0, 74.0, 78.0, 80.0, 79.0, 76.0, 72.0, 66.0]) rng = np.random.default_rng(0) levels = base + rng.normal(0.0, 0.5, size=(10, 8)) # (positions, bands) background = np.full((10, 8), 55.0) # ISO 3744 Annex B microphone coordinates on a radius-1.5 m hemisphere. mic_xyz = emission.measurement_positions("hemisphere", radius=1.5, reflecting_planes=1) print(mic_xyz.shape) # (10, 3) res = emission.sound_power_pressure( levels, "hemisphere", radius=1.5, reflecting_planes=1, background_levels=background, frequencies=freqs, room=emission.RoomEnvironment(reverberation_time=0.6, volume=300.0), # -> K2 ) print(round(res.surface_area, 2)) # 14.14 m^2 (= 2*pi*1.5^2) print(round(float(res.environmental_correction[0]), 2)) # K2 = 2.32 dB print(round(res.sound_power_level_a, 1)) # LWA = 92.4 dB print(round(res.uncertainty, 1)) # U = 3.0 dB (2*sigma_R0) print(np.round(res.sound_power_level, 1)) # per-band LW res.plot() # sound power level bars per band, LWA in the title (needs matplotlib) ``` *One bar per band: the energy-averaged surface pressure minus the background ($K_1$) and environmental ($K_2$) corrections plus the surface term $10\log_{10}(S/S_0)$ gives $L_W(f)$, and the A-weighted energy sum across bands gives the single-number $L_{W\mathrm{A}}$ in the title.*

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```python import matplotlib.pyplot as plt import numpy as np from phonometry import emission # Octave-band SPL (dB) at the 10 hemisphere positions of ISO 3744 (Annex B), # with the source running, plus the background spectrum with it switched off. freqs = np.array([63, 125, 250, 500, 1000, 2000, 4000, 8000]) base = np.array([70.0, 74.0, 78.0, 80.0, 79.0, 76.0, 72.0, 66.0]) rng = np.random.default_rng(0) levels = base + rng.normal(0.0, 0.5, size=(10, 8)) # (positions, bands) background = np.full((10, 8), 55.0) res = emission.sound_power_pressure( levels, "hemisphere", radius=1.5, reflecting_planes=1, background_levels=background, frequencies=freqs, room=emission.RoomEnvironment(reverberation_time=0.6, volume=300.0), # -> K2 ) # res is the SoundPowerResult computed above. One line: res.plot() plt.show() # By hand: a bar spectrum of LW with the A-weighted total in the title. freqs = res.frequencies positions = np.arange(freqs.size) fig, ax = plt.subplots() ax.bar(positions, res.sound_power_level, width=0.7, color="#1f77b4") ax.set_xticks(positions) ax.set_xticklabels([f"{f:g}" for f in freqs], rotation=45, ha="right") ax.set_xlabel("Frequency [Hz]") ax.set_ylabel("Sound power level LW [dB]") ax.set_title( f"Enveloping-surface sound power (ISO 3744) " f"LWA = {res.sound_power_level_a:.1f} dB(A)") plt.show() ```

The A-weighted total $L_{W\mathrm{A}}$ is combined from the band powers with the ISO 3744 Annex E A-weighting corrections, so it needs `frequencies`. Passing a `RoomEnvironment` as `room` (`reverberation_time` + `volume`, or `absorption_area`, or `mean_absorption_coefficient` + `room_surface`) enables $K_2$; omit it and the field is treated as free ($K_2 = 0$). If the background margin drops below the grade criterion or $K_2$ exceeds the validity limit, a `SoundPowerWarning` flags that the levels are upper bounds; the determination still returns. ### K1 and K2 pitfalls Both corrections subtract energy from the surface level, so overestimating either one understates the emission. That is why the standards cap them, and why most disputes over an enveloping-surface result trace back to one of these habits: - **$K_1$ has a cliff, not a slope.** At a 15 dB margin the correction is a negligible 0.14 dB; at the 6 dB engineering criterion it is already 1.26 dB, the largest value the grade accepts. Below the criterion the standard does not let the formula run on: $K_1$ is capped and the result is reported as an upper bound. Never extrapolate the subtraction into a smaller margin; raise the margin (quieter site, closer surface) or switch to the intensity method. - **$K_1$ assumes a stationary background.** The source-off reading must be taken at the same positions with the room in the same state, and the background energy must be the same during both readings. A ventilation system that cycles or a vehicle passing during either reading invalidates the pair; the energy subtraction also assumes source and background are incoherent, which holds for unrelated noise but not for the source's own reflections. - **$K_2$ removes the average room build-up, not discrete reflections.** A nearby wall, a trolley or another machine just outside the surface adds a specular contribution concentrated at a few microphones. That imbalance shows up in the apparent directivity index $DI_i^*$, and no room-average correction can remove it: move the surface, remove the reflector or treat it with absorption. - **$K_2$ is only as good as $A$.** With $A$ from Sabine ($0.16\,V/T$), errors in the reverberation time or the volume propagate directly. At the $K_2 = 4\ \text{dB}$ validity limit about 60 % of the measured energy is room, not source, and a 20 % error in $A$ still moves $L_W$ by about 0.5 dB. Prefer a measured $T_{60}$ over a guessed absorption coefficient, and keep the measurement distance small enough that $K_2$ stays well under the limit. ### `sound_power_pressure()` parameters | Parameter | Type | Units | Range / default | Notes | | :--- | :--- | :--- | :--- | :--- | | `levels_positions` | 2D array | dB | `(NM, NB)` | One row per position, one column per band (or a single A-weighted column) | | `surface` | str | — | `'hemisphere'` / `'box'` | Measurement-surface shape | | `radius` | float | m | > 0 (hemisphere) | Hemisphere radius $r$ | | `dimensions` | (float, float, float) | m | > 0 (box) | Reference-box $(l_1, l_2, l_3)$ | | `distance` | float | m | > 0 (box) | Measurement distance $d$ | | `reflecting_planes` | int | — | `1` / `2` / `3`, default `1` | Halves/quarters the hemisphere area | | `background_levels` | 2D array or spectrum | dB | `(NM, NB)`, or `(NB,)` / `(1, NB)` | Enables $K_1$; a single spectrum broadcasts to every position | | `frequencies` | 1D array | Hz | nominal band centres | Enables $L_{W\mathrm{A}}$ (Annex E) | | `room` | `RoomEnvironment` or None | — | default `None` (free field) | The room data behind $K_2$; its fields are the three routes to $A$ below | | `room.absorption_area` | float or 1D array | m² | > 0 | $A$ for $K_2$ (direct); per-band array → per-band $K_2$ | | `room.reverberation_time`, `room.volume` | float/array, float | s, m³ | > 0 | $A = 0.16\,V/T$ for $K_2$; per-band $T$ → per-band $K_2$ | | `room.mean_absorption_coefficient`, `room.room_surface` | float/array, float | —, m² | `(0,1]`, > 0 | $A = \alpha\,S_v$ (Eq. A.7); per-band $\alpha$ → per-band $K_2$ | | `grade` | str | — | `'engineering'` (default) / `'survey'` | ISO 3744 vs ISO 3746 | | `omc_uncertainty` | float | dB | default `0.0` | $\sigma_\text{omc}$, operating/mounting instability, folded into $U$ | Returns a `SoundPowerResult`: `sound_power_level` (per-band $L_W$), `surface_pressure_level` ($L_p$ after $K_1$/$K_2$), `mean_pressure_level`, `background_correction`/`environmental_correction` ($K_1$/$K_2$), `directivity_index` (apparent $DI_i^*$ per microphone position **and** frequency band, shape `(NM, NB)`; ISO 3744 clause 8.6), `surface_area`, `sound_power_level_a` ($L_{W\mathrm{A}}$), `uncertainty` (expanded, 95 %) and `grade`. `measurement_positions('hemisphere', radius=…, reflecting_planes=…, tones=…, grade=…)` returns the normative `(N, 3)` microphone coordinates (Table B.1 for tonal sources, B.2 for broadband). Those coordinates plot directly with `plot_microphone_positions`, which draws the array on its measurement surface in 3-D, numbered as in the standard. *Where the ten Annex B microphones actually sit on the 2 m hemisphere: the heights are staggered so the array samples the whole surface evenly, which is what lets the plain energy average of the ten levels stand in for the surface integral.*

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```python import matplotlib.pyplot as plt from phonometry import measurement_positions, plot_microphone_positions # The 10 ISO 3744 Annex B microphones on a 2 m hemisphere. plot_microphone_positions(measurement_positions("hemisphere", radius=2.0), radius=2.0) plt.show() ```

## 2. Precision grade, anechoic room (ISO 3745) When the highest accuracy is required, ISO 3745 measures sound power in a qualified **anechoic** or **hemi-anechoic** room, where the free field lets a fixed array of microphones sample the radiated sound pressure directly. It is the grade-1 counterpart to the enveloping-surface method of Section 1, with standardized microphone coordinates, a per-position background correction and an explicit meteorological correction. **Sound power level (Clause 8).** The band sound power level is the surface-averaged pressure level plus the surface term and the corrections: $$ L_W = \overline{L_p} + 10\log_{10}\frac{S}{S_0} + C_1 + C_2 + C_3, $$ with $S = 4\pi r^2$ over the sphere or $S = 2\pi r^2$ over the hemisphere, $S_0 = 1\ \text{m}^2$. $C_1$ and $C_2$ are the meteorological corrections (reference and radiation-impedance terms); $C_3$ accounts for air absorption over the measurement radius. The microphone positions are the standardized unit-vector arrays of Tables D.1 (sphere), E.1 (hemisphere) and E.2 (hemisphere, broadband). ```python import numpy as np from phonometry import emission # The 40 standardized hemisphere positions (unit vectors scaled by the radius). pos = emission.precision_positions("hemisphere", radius=1.0, count=40) print(pos.shape) # (40, 3) # Octave/third-octave band SPL (dB) at each of the 40 positions; here a uniform # 74 dB in one band. The result carries S = 2*pi*r^2 and LW with C1+C2+C3. levels = np.full((40, 1), 74.0) res = emission.sound_power_anechoic(levels, "hemisphere", radius=1.0) print(round(res.surface_area, 3)) # 6.283 (2*pi*1^2) print(np.round(res.sound_power_level, 2)) # [81.85] ``` **Background and meteorological corrections.** The $K_1$ background correction is applied **per position** and floored where the signal-to-background difference is small (Eq. 11); the meteorological correction is evaluated from the measured temperature and static pressure. ```python import numpy as np from phonometry import emission # K1 for a 6 dB signal-to-background difference in a <=200 Hz edge band: the # floor is 1.26 dB (Eq. 11). Source and background levels are [positions, bands]. k1 = emission.precision_background_correction( np.array([[56.0]]), np.array([[50.0]]), np.array([200.0])) print(round(float(k1[0, 0]), 4)) # 1.2563 # Meteorological corrections at the 23 C, 101.325 kPa reference (Eq. 16): mc = emission.meteorological_corrections(23.0, 101.325) print(round(mc.c1, 4), round(mc.c2, 4)) # -0.1282 0.0 # Expanded uncertainty (Clause 10.5 EXAMPLE): sigma_R0 = 0.5, sigma_omc = 2.0, # k = 2 -> U = 4.1 dB. print(round(emission.precision_uncertainty(0.5, 2.0, 2.0), 3)) # 4.123 ``` The `MeteorologicalCorrection` is a pair of scalars (plus the per-band $C_3$ when the attenuation coefficient is supplied per band) rather than a plottable spectrum: the corrections fold into the `PrecisionSoundPowerResult` as its `c1`/`c2`/`c3` fields, and the `.report()` fiche prints them on its measurement-basis strip. Over several bands `sound_power_anechoic` returns a plottable `PrecisionSoundPowerResult` carrying the per-band $L_W$ and the A-weighted total: ```python import numpy as np from phonometry import emission # A mid-frequency-peaked machine measured over the 40-position hemisphere array # (Annex E). levels_positions is the (40, NB) surface pressure spectrum: a base # spectrum peaked near 1 kHz plus a small per-position spatial spread. freqs = np.array([125, 250, 500, 1000, 2000, 4000, 8000], float) base = 70.0 + 8.0 * np.exp(-(np.log2(freqs / 1000.0) ** 2) / 2.0) rng = np.random.default_rng(7) levels = base[None, :] + rng.normal(0.0, 1.0, (40, freqs.size)) result = emission.sound_power_anechoic(levels, "hemisphere", radius=1.0, frequencies=freqs) print(round(result.sound_power_level_a, 1)) # 89.3 result.plot() # LW spectrum, LWA in the title (needs matplotlib) ``` *One bar per band: the surface-averaged pressure plus the area, background and meteorological corrections give $L_W(f)$, and the A-weighted energy sum across bands gives the single-number $L_{W\mathrm{A}}$ in the title.*

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```python import matplotlib.pyplot as plt import numpy as np from phonometry import emission # A mid-frequency-peaked machine measured over the 40-position hemisphere array # (Annex E). levels_positions is the (40, NB) surface pressure spectrum: a base # spectrum peaked near 1 kHz plus a small per-position spatial spread. freqs = np.array([125, 250, 500, 1000, 2000, 4000, 8000], float) base = 70.0 + 8.0 * np.exp(-(np.log2(freqs / 1000.0) ** 2) / 2.0) rng = np.random.default_rng(7) levels = base[None, :] + rng.normal(0.0, 1.0, (40, freqs.size)) result = emission.sound_power_anechoic(levels, "hemisphere", radius=1.0, frequencies=freqs) # result is the PrecisionSoundPowerResult computed above. One line: result.plot() plt.show() # By hand: a bar spectrum of LW with the A-weighted total in the title. freqs = result.frequencies positions = np.arange(freqs.size) fig, ax = plt.subplots() ax.bar(positions, result.sound_power_level, width=0.7, color="#1f77b4") ax.set_xticks(positions) ax.set_xticklabels([f"{f:g}" for f in freqs], rotation=45, ha="right") ax.set_xlabel("Frequency [Hz]") ax.set_ylabel("Sound power level LW [dB]") ax.set_title( f"Precision sound power (ISO 3745) LWA = {result.sound_power_level_a:.1f} dB(A)") plt.show() ```

## 3. The measurement report (`.report()`) A sound power determination ends as a *document*. Every result of this page stays plottable while it is being worked on (`res.plot()` draws the same $L_W$ spectrum interactively that the fiche typesets), and the report step wraps it into the deliverable. Both the enveloping-surface result (`SoundPowerResult`, ISO 3744/3746) and the precision result (`PrecisionSoundPowerResult`, ISO 3745) expose a `.report()` method that writes a one-page PDF fiche laid out like a sound-power test sheet: the standard-basis line naming the applied method and accuracy grade, an optional metadata header (client, noise source, test environment, instrumentation, climate, date), a per-band table (nominal octave/one-third-octave frequency, the surface sound-pressure level $L_p$ and the band sound-power level $L_W$), the sound-power spectrum $L_W(f)$ with a nominal band axis, and a boxed A-weighted sound power level $L_{W\mathrm{A}}$ (dB re 1 pW) with the total $L_W$, the expanded uncertainty $U$ and the measurement surface area $S$ alongside. The metadata is supplied through a `ReportMetadata`, whose applicable fields here are the **source description** (`specimen`), the **test environment** (`test_room`), the **client**, the **instrumentation**, the **temperature**, **relative humidity** and **ambient pressure**, the **date of test** (`test_date`) and the footer identity (`laboratory`, `operator`, `report_id`, `notes`); the measurement surface area $S$ comes from the result itself and is printed in the result box and the basis strip, together with the applied corrections (the background $K_1$ and environmental $K_2$ for the ISO 3744/3746 surface method, or the meteorological $C_1$/$C_2$/$C_3$ for the ISO 3745 precision method). Supplying `requirement` adds a PASS/FAIL verdict against a declared A-weighted sound-power limit (a sound-power emission is a quantity where less is better, so the source passes at or below the limit). `verbose=True` adds the energy-averaged level $L_p'$ to the table, and for the ISO 3744/3746 surface result it also adds the $K_1$/$K_2$ correction columns (the ISO 3745 precision result carries no $K_1$/$K_2$; its $C_1$/$C_2$/$C_3$ appear in the basis strip). `language="es"` renders the Spanish fiche with comma decimals. ```python import numpy as np from phonometry import ReportMetadata, emission freqs = np.array([63, 125, 250, 500, 1000, 2000, 4000, 8000], float) # Ten identical position spectra over a hemisphere of radius 4 m; background a # uniform 10 dB below and an equivalent absorption area A = 1500 m^2 (so K1, K2 # are meaningful and within the engineering validity limit). surface = np.array([72.0, 76, 80, 82, 81, 78, 73, 66]) res = emission.sound_power_pressure( np.tile(surface, (10, 1)), "hemisphere", radius=4.0, background_levels=np.tile(surface - 10.0, (10, 1)), frequencies=freqs, grade="engineering", room=emission.RoomEnvironment(absorption_area=1500.0), ) res.report( "sound_power.pdf", metadata=ReportMetadata( client="Example manufacturing plant", specimen="Hydraulic power pack (floor-standing)", test_room="Hemi-anechoic room over a reflecting floor", instrumentation="Class 1 sound level meter (IEC 61672-1), s/n 0042", laboratory="Phonometry reference example", report_id="EXAMPLE-3744", requirement=105.0, ), ) # LWA = 103.7 dB(A) re 1 pW -> declared limit 105 dB(A): PASS ``` The example fiche, regenerated with `make reports`, is kept rendered in the repository. Click the preview to open the PDF: [](https://raw.githubusercontent.com/jmrplens/phonometry/main/.github/reports/iso3744_sound_power_example.pdf) *Sound power determination fiche (`SoundPowerResult.report`), an ISO 3744 engineering-grade hemisphere measurement with the $K_1$/$K_2$ corrections and the boxed $L_{W\mathrm{A}}$.* The precision result writes the same sheet from the ISO 3745 side, with the meteorological corrections on its basis strip in place of the $K_1$/$K_2$ pair. This is the 40-position hemisphere measurement of section 2, the one whose spectrum is plotted above: ```python from phonometry import ReportMetadata result.report( "precision-sound-power.pdf", metadata=ReportMetadata( client="Example manufacturing plant", specimen="Mid-frequency-peaked machine", test_room="Qualified anechoic room, 40-position hemisphere array", measurement_standard="ISO 3745", ), ) # LWA = 89.3 dB(A) re 1 pW, U = 4.1 dB ``` [](https://raw.githubusercontent.com/jmrplens/phonometry/main/.github/reports/iso3745_precision_power_example.pdf) *Precision sound power fiche (`PrecisionSoundPowerResult.report`), the ISO 3745 anechoic determination: no $K_2$ at all, a 6.28 m² hemisphere instead of a 100 m² one, and $U$ = 4.1 dB because the operating-and-mounting term dominates the reproducibility one.* ## See also - [Sound Power](https://jmrplens.github.io/phonometry/devices/emission/sound-power/): choosing among the five determination routes, what the accuracy grades promise, and the ISO 4871 noise-emission declaration a measured $L_{W\mathrm{A}}$ feeds. - [Sound Power in the Reverberation Room (ISO 3741)](https://jmrplens.github.io/phonometry/devices/emission/sound-power-reverberation/): the precision-grade diffuse-field alternative when the source can travel to a qualified room. - [Sound Power by Intensity Scanning (ISO 9614)](https://jmrplens.github.io/phonometry/devices/emission/sound-power-intensity/): the routes that tolerate the steady background noise a pressure method cannot subtract. - [Room Acoustics](https://jmrplens.github.io/phonometry/buildings/rooms/room-acoustics/): the reverberation time and equivalent absorption area that feed $K_2$. - [Levels](https://jmrplens.github.io/phonometry/signals/levels/levels/): energy averaging and the A-weighting behind $L_{W\mathrm{A}}$. - [Theory](https://jmrplens.github.io/phonometry/reference/theory/environment-transport/): the $K_1$/$K_2$ and $C_1$/$C_2$ derivations. - API reference: [`emission.sound_power`](https://jmrplens.github.io/phonometry/reference/api/power/sound-power/). ## References - Beranek, L. L., & Mellow, T. J. (2012). *Acoustics: Sound fields and transducers*. Academic Press. ISBN 978-0-12-391421-7. [doi:10.1016/C2011-0-05897-0](https://doi.org/10.1016/C2011-0-05897-0). Radiation and sound fields: the free-field relations between pressure and power that the enveloping-surface and anechoic methods rest on. - International Organization for Standardization. (2010). *Acoustics — Determination of sound power levels and sound energy levels of noise sources using sound pressure — Engineering methods for an essentially free field over a reflecting plane* (ISO 3744:2010). [iso.org catalogue](https://www.iso.org/standard/52055.html). The enveloping-surface method of section 1. - International Organization for Standardization. (2012). *Acoustics — Determination of sound power levels and sound energy levels of noise sources using sound pressure — Precision methods for anechoic rooms and hemi-anechoic rooms* (ISO 3745:2012). [iso.org catalogue](https://www.iso.org/standard/45362.html). The precision anechoic-room method of section 2. - International Organization for Standardization. (2010). *Acoustics — Determination of sound power levels and sound energy levels of noise sources using sound pressure — Survey method using an enveloping measurement surface over a reflecting plane* (ISO 3746:2010). [iso.org catalogue](https://www.iso.org/standard/52056.html). The survey grade of section 1, sharing the enveloping-surface formulae with coarser criteria. ## Standards ISO 3744:2010, *Acoustics — Determination of sound power levels and sound energy levels of noise sources using sound pressure — Engineering methods for an essentially free field over a reflecting plane*: the enveloping-surface method: hemisphere and box surface areas, the $K_1$/$K_2$ corrections, the Annex B microphone positions and the Annex E A-weighting. ISO 3746:2010, *… Survey method using an enveloping measurement surface over a reflecting plane*: the survey grade sharing the same formulae with coarser criteria. ISO 3745:2012, *… Precision methods for anechoic rooms and hemi-anechoic rooms*: the Clause 8 power level, the per-position background correction (Eq. 11), the meteorological corrections and the standardized microphone arrays of section 2. **Not covered.** Neither method performs the facility qualification it assumes: ISO 3745's free-field qualification of the anechoic or hemi-anechoic environment is taken for granted, and ISO 3744's $K_2$ validity only warns. ISO 3744 **Annex G**, the correction to reference meteorological conditions required above 500 m of altitude or below 10 °C (clause 8.2.5), is not applied either: `sound_power_pressure` takes no temperature or pressure argument. The $C_3$ meteorological correction of ISO 3745 needs an air-absorption coefficient the caller supplies through `air_absorption_coefficient=`; this module does not compute it from **ISO 9613-1** itself.