Source: https://jmrplens.github.io/phonometry/reference/api/filters/weighting-compliance/ IEC 61672-1:2013 frequency-weighting class verification. A/C/Z frequency-weighting acceptance limits transcribed from BS EN 61672-1:2013, **Table 3** (standard page 22): the design-goal responses and the class 1 and class 2 upper/lower limits at the 34 nominal frequencies from 10 Hz to 20 kHz. A lower limit of `-inf` means only the upper limit applies (subclause 5.5.6 checks measured deviations at the nominal frequencies). The historical **B weighting** is verified against ANSI S1.4-1983: design goals from the B column of **Table IV** (whose A and C columns equal IEC 61672-1:2013 Table 3 digit for digit) and tolerance limits from **Table V**, whose instrument Types 1 and 2 fill the class 1 / class 2 verdict slots (the stricter laboratory Type 0 mask is exercised by the CI conformance report). The **AU weighting** is verified against IEC 61012:1990: design goals are the sum of the nominal A response and the **Table 1** nominal U response (with the subclause 2.2 explicit AU values at 25/31.5/40 kHz), checked against the Table 1 tolerances for the filter as a separate unit, the tighter of the two tolerance readings the standard offers. IEC 61012 publishes a single tolerance set, so both verdict slots carry the same margin for AU. One subject: the weighting network a sound level meter applies to the whole signal, whose acceptance limits qualify the deviation of its measured relative response from a design goal at the nominal frequencies. The band-filter class limits of IEC 61260-1, which qualify a relative attenuation against a mask around each mid-band frequency, live in [`phonometry.filters.compliance`](/phonometry/reference/api/filters/compliance/). > Auto-generated from the source docstrings by `scripts/generate_api_docs.py` (`make api-docs`). Do not edit by hand. ## verify_weighting_class ```python verify_weighting_class( wf: WeightingFilter, *, sweep_points: int = 4096, ) -> dict[str, Any] ``` Verify a frequency-weighting filter against its standard's tolerances. `A`/`C`/`Z` are checked against IEC 61672-1:2013 Table 3 (classes 1 and 2). The historical `B` weighting is checked against ANSI S1.4-1983: Table IV design goals with the Table V tolerance limits, whose instrument Types 1 and 2 fill the class 1 / class 2 verdict slots (an `overall_class` of 1 then reads "ANSI S1.4-1983 Type 1"). `AU` is checked against IEC 61012:1990: design goals are nominal A + nominal U (Table 1, plus the subclause 2.2 explicit AU values at 25/31.5/40 kHz) with the single Table 1 tolerance set for the filter as a separate unit, so both class slots carry the same margin and `overall_class` is 1 (complies) or `None`. `G` is not supported here (ISO 7196 defines one +/-1 dB instrumentation tolerance, no class structure; the CI conformance report pins it), nor is `D` (the tolerance tables of the withdrawn IEC 537 did not survive it; the conformance report pins the D response against its published transfer function and tabulated curve). The filter's relative response (normalized to its 1 kHz gain) is evaluated at the *exact* base-10 frequency behind each nominal label below the Nyquist frequency (IEC 61672-1 Table 3 NOTE: the design goals are computed at $f = 1000 \cdot 10^{0.1 (n - 30)}$, e.g. 15 848.9 Hz for "16 kHz"; IEC 61672-3:2013 subclause 13.3 tests the deviation at the same exact frequencies, and IEC 61012 Table 1 lists the same exact frequencies). The deviation from the design-goal weighting is checked against the two acceptance masks. A dense logarithmic sweep between the checked frequencies additionally enforces IEC 61672-1 subclause 5.5.7: at any frequency between two adjacent nominal frequencies, the deviation of the response from the analytic design goal (Annex E for A/C/Z, the ANSI S1.4-1983 Appendix C formulas for B, the A response cascaded with the IEC 61012 Table 2 poles for AU) must stay within the *larger* of the two adjacent limits. Without it a resonance or notch between the nominal frequencies would go unnoticed (for B and AU the sweep is applied as the analogous engineering check). Both the per-frequency verdicts and the sweep must pass for `overall_class`. The sweep samples `sweep_points` grid frequencies; a violation narrower than the grid spacing could in principle fall between samples, so raise `sweep_points` for higher-Q suspects (the verdict attests the sampled grid, not a continuous proof). The response is taken from the designed second-order sections (evaluated with `sosfreqz` at their design rate), so it is exact and deterministic; it does not model the runtime resampling stages that `high_accuracy` adds around them, whose anti-alias response is flat across the audio band checked here. The `Z` weighting is a flat bypass and always complies. When rows that carry a *finite lower* acceptance limit fall at or above the Nyquist frequency (e.g. the 8-16 kHz class 1 rows of a 16 kHz sampled system, or the 25-40 kHz AU rows of a 48 kHz one), they cannot be checked and `range_limited` is `True`: the returned class then attests conformance over the checked frequencies only, not conformance over the standard's full frequency range. **Parameters** | Name | Description | | :--- | :--- | | `wf` | The weighting filter to verify (`A`, `B`, `C`, `AU` or `Z`). | | `sweep_points` | Number of points of the 5.5.7 between-nominals sweep (>= 64). | **Returns:** Dict with `overall_class` (1, 2 or None), `range_limited` (see above), `bands`: a list of `{"freq", "class", "deviation_db", "margin_class1_db", "margin_class2_db"}` where `freq` is the nominal label, a positive margin means the limits are met with that much room, and `between_nominals`: `{"worst_freq", "margin_class1_db", "margin_class2_db"}` for the sweep. ## weighting_class_limits ```python weighting_class_limits( weighting_class: int, ) -> tuple[np.ndarray, np.ndarray, np.ndarray] ``` IEC 61672-1:2013 Table 3 acceptance limits for a performance class. The limits apply to every IEC 61672-1 weighting (A, C, Z); they qualify the deviation of the measured relative response from the design goal at each nominal frequency, not the response itself. (The B and AU masks that `verify_weighting_class` uses come from ANSI S1.4-1983 Table V and IEC 61012:1990 Table 1 instead and are not returned here.) **Parameters** | Name | Description | | :--- | :--- | | `weighting_class` | 1 or 2 (IEC 61672-1:2013 performance class). | **Returns:** Tuple `(frequencies, lower, upper)` of the 34 nominal frequencies (Hz) and the lower/upper deviation limits in dB. A lower limit of `-inf` means only the upper limit applies.