Errata in published sources

Implementing a standard clean-room means re-deriving every formula, constant and worked example from the source document rather than from anyone else’s code. Done across hundreds of documents, that process finds defects in the sources themselves: a worked example that contradicts its own normative clause, a constant with a digit dropped in typesetting, a cross-reference that points at the wrong equation.

This page is the registry of those findings. Each entry names the printed edition and the exact location, quotes what the document says, shows why it cannot be right, gives the independent evidence, and states which reading the library implements and which regression test pins it. A defect listed here is never a defect of the method: in every case the intended reading could be established from the document itself or from physics.

Read it alongside the conformance report, which shows the numbers the library computes; this page explains the handful of places where the printed expected value is the thing that is wrong.

The registry is maintained in docs/ERRATA.md and transplanted here at build time by make site-reports, so the two cannot disagree.

During the clean-room implementation of this library, every formula, constant and worked example is re-derived and recomputed independently from the source documents. That process occasionally surfaces defects in the sources themselves: misprints, worked examples that contradict their own normative text, and ambiguous wording. This file records each confirmed case with the evidence, what the library does about it, and whether it has been reported.

The registry covers every kind of published source the library implements from: standards (ISO, IEC, EN), guidance documents and technical reports (EASA, ECAC, NRL), textbooks and journal papers. Non-normative sources are marked as such in their entry.

Entries describe the specific printed editions cited. A defect listed here is not a defect of the method; in every case the intended reading could be established from the document itself or from physics, and the library implements that reading with a regression test pinning it.

Status legend: unreported (recorded here only) / reported (submitted to the issuing body, with date and reference).

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ISO 717-2:2020, Annex C, example C.1 (CI of the bare floor)

• Location: Annex C, Table C.1 and the accompanying CI computation.
• The print: the 2020 reprint states CI = −10 for the bare-floor example.
• The problem: its own normative clause A.2.1 defines CI from the energy sum over 100 Hz to 2500 Hz (the first fifteen one-third-octave bands). The 2020 reprint’s value only reproduces if the 3150 Hz band is included in the sum (83,5238 dB, rounded 84), contradicting A.2.1. The correct sum over 100 to 2500 Hz is 83,2613 dB, rounded 83, giving CI = −11.
• Evidence: independent recomputation of both sums from the printed per-band levels; the 2013 edition of the same example prints CI = −11.
• Library behaviour: implements A.2.1 as written and pins CI = −11 with the 2013 print as the oracle (tests/reference_data.py, conformance check “ISO 717-2 Annex C, Table C.1”).
• Status: unreported.

ISO 717-2:2020, Annex C, example C.2 (covered floor: 800 Hz value and CI chain)

• Location: Annex C, Table C.2 (ΔLw / ΔLlin worked example).
• The print: (a) the 800 Hz reference-floor value is printed as 71,0 dB; (b) the CI line prints “Ln,sum = 75,252 7… = 75 dB” and “CI = 75 − 15 − 63 = −3 dB”, feeding “ΔLlin = 78 − 11 − (63 − 3) = 7 dB”.
• The problem: two independent defects. (a) The normative Table 4 reference floor is 71,5 dB at 800 Hz; the 71,0 dB row is a misprint, though after rounding it does not change the example’s CI (the correct energy sum rounds to 76 dB with either value). (b) The printed 75,2527 dB is exactly the energy sum of the wrong column over the wrong range: the measured floor “with covering” over all sixteen bands 100 Hz to 3150 Hz. A.2.1 defines CI from the reference floor with covering (the “Ln,r,0 − ΔL” column) over 100 Hz to 2500 Hz (15 bands), which gives 75,674 dB (printed chain) or 75,710 dB (Table 4 values) — both round to 76 dB, so CI,r = 76 − 15 − 63 = −2 either way, giving CI,Δ = −11 − (−2) = −9 and ΔLlin = 6 dB, not the printed −3 / −8 / 7 dB chain.
• Evidence: independent recomputation of every candidate sum from the printed per-band values; the printed 75,2527 reproduces to all printed digits only as the 16-band sum of the with-covering column.
• Library behaviour: derives the covered reference floor from the normative Table 4 values and sums per A.2.1, pinning ΔLw = 15 dB and CI,Δ = −9; the conformance check notes the provenance explicitly.
• Status: unreported.

ISO 2631-5:2018, Annex C, NOTE 5 (female worked example)

• Location: Annex C, NOTE 5 (64 kg female, mz = 0,025 MPa/(m/s²)).
• The print: R = 0,97.
• The problem: exact recomputation of Formula (C.3) with the note’s own inputs (mz = 0,025, age coefficient 0,039, b = 20, n = 20, N = 120) gives R = 0,9621, which rounds to 0,96. The same code reproduces the male example exactly (R = 1,2200 = printed 1,22), and the note’s Sd = 1,40 MPa matches the exact 1,3992, so the discrepancy is confined to the last digit of the printed female R.
• Evidence: hand recomputation of the C.3 sum, term by term.
• Library behaviour: computes the exact value; the test anchor keeps the printed 0,97 with a tolerance that documents the recomputed 0,9621.
• Status: unreported.

EN 12354-1:2000 Annex E.5 / ISO 12354-1:2017 E.3.4 (K24 clamp misprint)

• Location: EN 12354-1:2000, Annex E, clause E.5, and ISO 12354-1:2017, E.3.4 NOTE 4 (wall junction with flexible interlayers).
• The print: the bound on the K24 junction term is printed as “0 ≤ K24 ≤ −4 dB”, an empty interval; the 2017 edition repeats the 2000 misprint verbatim.
• The problem: the interval is impossible as printed; the accompanying figure and the physics (the term is a reduction bounded below) indicate −4 dB ≤ K24 ≤ 0 dB.
• Evidence: page render of the printed clause; corroboration against the figure’s curve family.
• Library behaviour: implements the clamp as −4 ≤ K24 ≤ 0 with a misprint note in the docstring.
• Status: unreported.

EN 12354-1:2000, Figure E.9 (E.7) (K24 stated in the figure-axis mass ratio)

• Location: Annex E, Figure E.9 / Formula (E.7) (junction of lightweight double leaf wall and homogeneous elements), the K24 line.
• The print: K24 = 3,0 − 14,1 M + 5,7 M² dB (for m2/m1 > 3), under a figure whose x-axis is m2/m1.
• The problem: Annex E defines M per transmission path as M = lg(m’⊥,i/m’i) (perpendicular element over the element carrying the path). The K24 path 2→4 is carried by the homogeneous element (m2 = m4) with the leaf (m1) perpendicular, so the per-path M is lg(m1/m2) — but the printed K24 line only matches its own figure’s curve when M is read as the x-axis variable lg(m2/m1) (e.g. −2,4 dB at m2/m1 = 3, −5,4 dB at 10). Read with the annex’s declared M, the line contradicts the figure by 28,2·|lg(m2/m1)| dB. The same edition’s other K24 line (Figure E.5, Formula (E.5)) does follow the declared per-path M, so the two K24 prints of the 2000 edition silently use different conventions. ISO 12354-1:2017 E.3.5 prints the relation consistently in the per-path convention of its Formula (E.3), K24 = 3,0 + 14,1 M + 5,7 M²; the two editions agree numerically (an earlier revision of this entry read the 2017 print as a sign misprint — re-derivation against both editions’ figures shows it is a convention recast, not a defect of the 2017 text).
• Evidence: page renders of both editions (EN 12354-1:2000 printed pp. 43, 46, 48; ISO 12354-1:2017 printed pp. 43, 46-47); numerical evaluation of both forms against the Figure E.9 curve.
• Library behaviour: implements the per-path convention uniformly (junction_vibration_reduction, mass_ratio = m’⊥,i/m’i for every branch), so the E.7 double-leaf branch takes leaf-over-homogeneous ratios below 1/3 and evaluates 3,0 + 14,1 M + 5,7 M².
• Status: unreported.

EN 12354-2:2000, Formula (3) vs Annex E.3 (standardized impact level)

• Location: Formula (3) and worked example E.3.
• The print: Formula (3) defines L’nT = L’n − 10 lg(0,16·V/(A0·T0)), which reduces exactly to L’n − 10 lg(0,032·V), i.e. a reference volume of 31,25 m³. Annex E.3 states “from equation (3): L’nT,w = L’n,w − 10 lg(V/30)”.
• The problem: the annex’s V/30 is a rounding of the formula’s own constant; the two differ by a constant 0,177 dB.
• Evidence: direct algebra; both variants recomputed for the E.3 case (42,959 vs 42,782 dB, both rounding to 43 in that example).
• Library behaviour: implements the exact 0,032·V form and documents the annex’s rounding.
• Status: unreported.

EN 12354-3:2000, Annex F (worked example internal inconsistencies)

• Location: Annex F worked example.
• The print: (a) the printed D2m,nT row equals R’ + 1,5 dB; (b) the printed high-frequency-band row is inconsistent with the example’s own partial indices.
• The problem: Formula (13) with the example’s own inputs (V = 50 m³, S = 11,3 m², T0 = 0,5 s) gives D2m,nT = R’ + 1,69 dB, not +1,5 dB; and the high-band row cannot be reproduced from the example’s stated partial results (the self-consistent values are 35,8/38,0 dB).
• Evidence: recomputation of Formula (13) and of the partial-index chain. The example’s single-number result D2m,nT,w = 33 dB is insensitive to both and still reproduces.
• Library behaviour: implements Formula (13); the test data notes both inconsistencies next to the affected anchors.
• Status: unreported.

ISO 15186-1:2000, Clause 3.9, Formula (8) (sign of the 10 lg N term)

• Location: Clause 3.9, Formula (8), the intensity element normalized level difference for N small building elements measured together.
• The print: DI,n,e = Lp1 − 6 − (LIn + 10 lg(Sm/A0) + 10 lg(N)), i.e. the 10 lg N term is subtracted.
• The problem: the subtracted sign cannot be derived. Measuring N identical units within one measurement surface raises the transmitted power (and hence LIn + 10 lg Sm) by 10 lg N, so recovering the per-unit DI,n,e requires adding 10 lg N. The pressure-based equivalent, ISO 10140-2:2010 Formula (6), prints exactly that correction (Dn,e = L1 − L2 + 10 lg(nA0/A)), and ISO 15186-2:2010 Formula (12) prints Formula (8) without any N term (the N = 1 case, with which both signs agree). As printed, installing more units would lower the per-unit rating by 20 lg N relative to the derivable value.
• Evidence: page render of the printed formula; derivation from the diffuse-field receiving-room relation L2 = LW + 10 lg(4/A) against ISO 10140-2:2010 Formula (6); cross-check against ISO 15186-2:2010 Formula (12) and Hopkins, Sound Insulation (2007), Eq. 3.45.
• Library behaviour: implements the derivable per-unit form (intensity_element_normalized_difference, +10 lg N) and emits a warning whenever n > 1, where the result deviates from the print.
• Status: unreported.

ISO 10848-1:2006, Clause 8.1.1, Formula (20) (spurious π in the critical frequency)

• Location: Clause 8.1.1, Formula (20), the thin-plate critical frequency used by the test-facility flanking criterion of Formula (19).
• The print: fc = c0² / (1,8 cL · h · π).
• The problem: the constant 1,8 is itself the rounded 2π/√12 ≈ 1,814 of the thin-plate dispersion relation, so the extra π double-counts it and would misplace fc by a factor π (e.g. a 100 mm concrete element with cL = 3500 m/s: 187 Hz without the π, 59 Hz with it, far from any measured coincidence dip).
• Evidence: derivation from the thin-plate dispersion relation (Hopkins, Sound Insulation (2007), Eq. 2.201, fc = c0²/(1,8 cL h)); ISO 12354-1:2017 prints the same π-free form in its symbol definitions (fc = c0²/(1,8 cL t)).
• Library behaviour: implements the π-free form (phonometry.building.flanking_transmission.critical_frequency), with a misprint note in the docstring.
• Status: corrected upstream — ISO 10848-1:2017 (second edition) prints the π-free form in its Formula (5), fc = c0²/(1,8 h cL), confirming the 2006 print as a misprint. No report is needed. The entry is retained because the library cites the 2006 edition, whose print carries the defect; the 2017 edition stands as the confirmation.

ISO 12999-1:2020, Table 4 (missing 500 Hz row)

• Location: Table 4 (in-situ uncertainties per band).
• The print: the 2020 edition’s table omits the 500 Hz row that the 2014 edition prints (situation B 1,2 dB / situation C 0,8 dB).
• The problem: likely an editorial omission; the surrounding rows are unchanged between editions and the text does not mention removing the band.
• Evidence: side-by-side comparison of the 2014 and 2020 prints.
• Library behaviour: follows the 2020 print as published, with the omission documented in the module.
• Status: unreported.

ISO 12999-2:2020, Clause 8 wording vs Tables 4 and 5

• Location: Clause 8 (expression of results) and Tables 4/5.
• The print: the clause wording instructs rounding the standard uncertainty u before forming the expanded uncertainty U = k·u.
• The problem: the document’s own Tables 4 and 5 only reproduce when U is computed from the unrounded u and rounded last; the literal clause wording fails half of the printed table entries.
• Evidence: recomputation of all 25 table entries under both conventions (round-last: 25 of 25 match; round-first: 10 of 20 mismatch).
• Library behaviour: rounds last, matching the tables; the convention is documented and tested.
• Status: unreported.

ISO 10052:2021, Table 4 volume-range header

• Location: Table 4 (reverberation-index estimator), volume-range header.
• The print: the header reads “60 ≤ V < 150” while the body text says the method applies to rooms “up to 150 m³”.
• The problem: the boundary V = 150 m³ is included by the text and excluded by the header.
• Evidence: direct comparison of header and clause text.
• Library behaviour: accepts V = 150 (follows the text), with the ambiguity noted.
• Status: unreported.

ISO 17208-2:2019, Clause 5 uncertainty band coverage

• Location: Clause 5 (representative expanded uncertainties).
• The print: 5 dB for the low-frequency bands (10 Hz to 100 Hz), 3 dB for the mid-frequency bands (125 Hz to 16 000 Hz), 4 dB for the high-frequency bands (above 20 000 Hz).
• The problem: the band list leaves the 20 kHz one-third-octave band unassigned (nothing covers 16 kHz to 20 kHz inclusive).
• Evidence: the clause’s own enumeration.
• Library behaviour: applies the conservative 4 dB high-band value from just above 16 kHz, with the gap documented.
• Status: unreported.

ECMA-418-1:2024 (3rd edition), clause 4.1.2 (upper limit of the range of interest)

• Location: clause 4.1.2, the stated frequency range of interest for discrete tones.
• The print: “between 89,1 Hz and 11 220 Hz inclusive”.
• The problem: every formula and table of the standard uses 11 200 Hz: the Table 2/3 band-edge fits end at 11 200 Hz, and Formulae (13)/(26) treat the upper end of the criterion range consistently with 11 200 Hz. No other clause mentions 11 220 Hz.
• Evidence: cross-check of the clause 4.1.2 prose against Tables 2 and 3 and the criterion formulas of clauses 11.5/12.6.
• Library behaviour: uses the internally consistent 89,1 Hz to 11 200 Hz range (upper end exclusive per the formulas), with a code note in tonality.py.
• Status: unreported.

ECMA-418-2:2025 (4th edition), clause 5.1.5.2 (last block index)

• Location: clause 5.1.5.2, the segmentation of the zero-padded signal for the roughness/fluctuation-strength block sizes.
• The print: the index of the last block is given as l_last = ceil((n + s_b)/s_h).
• The problem: the formula is internally inconsistent: blocks placed at that index overrun the zero-padded signal defined by clause 5.1.2.2, and the resulting Formula (103) time grid becomes non-monotonic. The only self-consistent reading is to stop at the last block that fits inside the padded signal and align it flush with its end.
• Evidence: direct evaluation of the block start indices against the padded length for the clause 7.1.1 block/hop sizes; the flush-to-end reading reproduces the Clause 7 roughness calibration (1 asper) to 0,9999.
• Library behaviour: implements the flush-to-end reading with a code note in roughness_ecma.py.
• Status: unreported.

ECMA-418-2:2025 (4th edition), clause 9.1.4, Formula (127) (HSA kernel phase)

• Location: clause 9.1.4, Formula (127), the spectral kernel of the envelope analysis window used by the High-resolution Spectral Analysis.
• The print: the kernel’s phase factor is exp(−j·2π·f_n(k)·(s̃_b − n_ze + n_zb − 1)).
• The problem: the kernel is, by construction, the DFT of the rectangular analysis window of Formula (120) modulated to the candidate rate; that is the model Formula (124) fits to the measured DFT spectrum. That DFT has the phase exp(−j·π·f_n·(s̃_b − n_ze + n_zb − 1)); the printed factor doubles it (and is also inconsistent with the π arguments of the printed sine terms of the same formula). With the printed phase the fitted model cannot reproduce the spectrum of a noiseless windowed sinusoid, contradicting the clause’s own statement that the HSA achieves “theoretically infinite resolution for signals without noise”.
• Evidence: independent derivation of the window DFT plus numerical recomputation: with π the least-squares fit recovers the constant part, amplitudes and phases of synthetic noiseless envelopes to machine precision and the Formula (135) residual vanishes; with the printed 2π the kernel deviates from the window DFT by amounts of the order of the kernel itself and the residual stays of the order of the signal energy.
• Library behaviour: implements the π reading, pinned by a regression test on the exact recovery of synthetic line pairs.
• Status: unreported.

ECMA-418-2:2025 (4th edition), clause 9.1.5, Formula (144) (bin offset)

• Location: clause 9.1.5, Formula (144), the modulation rate of a local maximum of the envelope power spectrum.
• The print: the rate is the three-bin amplitude-weighted centroid of the peak position minus one, scaled by Δf.
• The problem: clause 9.1.4 (below Formula (122)) defines the spectral index k as mapping to the modulation rate k·r̃_s/s̃_b with k starting at 0. A symmetric local maximum at bin k has centroid k, and the printed formula then assigns it the rate (k − 1)·Δf, one full bin (0,73 Hz) low, which at fluctuation-strength rates is fatal (a true 1,46 Hz modulation would be reported as 0,73 Hz). The offset is only consistent with 1-based spectral-line positions, contradicting the standard’s own definition of k.
• Evidence: cross-check of Formula (144) against the k-to-rate mapping stated below Formula (122).
• Library behaviour: uses the centroid directly (no offset) with the 0-based k of Formula (122).
• Status: unreported.

ECMA-418-2:2025 (4th edition), clause 9.1.7 (units of the fine-tuning constants)

• Location: clause 9.1.7, Formulae (149)-(152), the damped Newton fine tuning of the dominant modulation rate.
• The print: differential step Δx = 10⁻⁵, damped-step cap 2·10⁻⁴, stop tolerance 10⁻⁷ and an iteration limit of 40, with the starting point x₀ = f̃_c,imax (a rate in Hz) and the failure check |f_c,1,opt − f̃_c,imax| > 1,25·Δf.
• The problem: the constants carry no units. Read in Hz, the damped step is capped at 5·10⁻⁵ Hz per iteration (2·10⁻³ Hz over all 40 iterations), so the tuning cannot move appreciably and the 1,25·Δf (≈ 0,92 Hz) failure check is unreachable; the whole clause would be inert. Read as normalized modulation rates f/r̃_s (the variable in which the Formula (127) kernel frequencies are expressed), the same constants give a 0,075 Hz damped per-iteration cap (≈ 2,9 Hz over the 39 iterations), a 1,5·10⁻⁴ Hz stop tolerance and a reachable failure check, all consistent with the clause’s purpose.
• Evidence: dimensional analysis of the printed constants against the 0,7324 Hz spectral resolution and the failure threshold.
• Library behaviour: applies the constants as normalized modulation rates.
• Status: unreported.

ECMA-418-2:2025 (4th edition), clause 9 introduction (broken cross-reference)

• Location: clause 9, third paragraph of the introduction, on the HSA-based loudness prediction.
• The print: “loudness scaling is improved by using HSA-based loudness prediction (see Clause 0)”.
• The problem: “Clause 0” does not exist; the HSA-based loudness scaling is described in clause 9.1.10 (an unresolved field reference).
• Evidence: the clause listing of the standard itself.
• Library behaviour: none required (the intended target is unambiguous).
• Status: unreported.

ISO/PAS 20065:2016, clause 5.3.4 (edge steepness of a distinct tone)

• Location: clause 5.3.4, Formulae (10)/(11), the minimum edge steepness of a distinct tone.
• The print: asymmetric formulas: the lower-edge steepness is scaled by f_T/2 and the upper-edge steepness by f_T (no divisor).
• The problem: the parent standard DIN 45681:2005-03 prints f_T/sqrt(2) on both edges, and its executable Annex J reference program does the same (Frequenz(i)/Sqr(2)). The two prints cannot both be satisfied; the ISO version is plausibly a typesetting corruption of the sqrt(2) factor (the radical dropped on one edge and halved on the other). Versus the DIN program the ISO print is sqrt(2) more lenient on the lower edge and sqrt(2) stricter on the upper; borderline tones with one-sided edge steepness around 17 to 34 dB/octave flip classification between the two readings.
• Evidence: side-by-side comparison of the ISO print, the DIN 45681 print and the DIN Annex J program.
• Library behaviour: follows the DIN/sqrt(2) reading (it matches the only executable reference), with the choice recorded in tone_audibility.py.
• Status: unreported.

DIN 45681:2005-03, Anhang I, Tabelle I.6, row “6 FG”

• Location: Anhang I, Beispiel I.2 (combustion engine, spectrum j = 1), Tabelle I.6, the combined row “6 FG” for the three tones k = 6/7/8 (592,2 / 629,8 / 643,3 Hz, tone levels 78,31 / 75,00 / 79,75 dB).
• The print: L_T = 81,11 dB together with delta L = 9,12 dB (with L_S = 59,53, L_G = 76,16, a_v = -2,40 at 592,2 Hz).
• The problem: the two cells contradict each other. The printed delta L = 9,12 dB only reproduces from the plain Formula (17) energy sum of the three tone levels (82,87 dB): 82,87 - 76,16 + 2,40 = 9,11. The printed L_T = 81,11 dB is consistent instead with the Anmerkung 2 shared-line dedupe (the 629,8/643,3 Hz tonal runs overlap), which would give delta L = 7,35 dB. Every other FG row of the annex is internally consistent (e.g. “2 FG”: L_T = 72,15, delta L = 9,18, both from the same sum; no lines shared there).
• Evidence: recomputation of both readings from the printed per-tone levels of Tabelle I.6; the same-page “2 FG” row as the consistent control.
• Library behaviour: combined_tone_level follows Anmerkung 2 (shared lines counted once), which reproduces the printed “2 FG” oracle; for the “6 FG” row only the delta L chain is pinned, with the contradiction recorded in tests/reference_data.py.
• Status: unreported.

IEC 60268-3:2013, clause 14.12.9.2 f) (DIM denominator)

• Location: clause 14.12.9.2, item f), the formula for the dynamic intermodulation distortion d_DIM.
• The print: the denominator of the printed formula is “U2”.
• The problem: the defining clause 14.12.9.1 states the ratio of the r.m.s. sum of the Table 2 intermodulation product voltages “to the amplitude of the output voltage at the frequency f_s”, i.e. the 15 kHz sine component U_s, the Otala convention. The symbol U2 is used throughout 14.12 for the total output voltage, which contradicts 14.12.9.1 (the test signal is dominated by the 3,15 kHz square wave, so the two denominators differ by several dB). Item d) of the same clause measures “the amplitudes of the sinusoidal signal U_s”, which the f) formula then never uses.
• Evidence: side-by-side reading of 14.12.9.1, 14.12.9.2 d) and 14.12.9.2 f); the historical DIM literature (Otala) defines the ratio to the sine amplitude.
• Library behaviour: follows the 14.12.9.1 definition (reference = the output amplitude at f_s), with a code comment at the reference measurement in distortion.py.
• Status: unreported.

ISO/PAS 1996-3:2022, Clause 5 (cross-references of r and d)

• Location: Clause 5, Formula (2), the definitions of the symbols of the prominence P = 3 lg[r/(dB/s)] + 2 lg(d/dB).
• The print: “r is the onset rate (OR) as defined in 3.4” and “d is the level difference (LD) as defined in 3.5”.
• The problem: the two cross-references are swapped. The document’s own terms and definitions set 3.4 as the level difference LD (“difference in decibels of L_pAF between the level of the end point L_e and the level of the starting point L_s of the onset”) and 3.5 as the onset rate OR (“slope in decibels per second of the straight line that gives the best approximation to the onset”). Read literally, Formula (2) would take three times the logarithm of a level difference plus twice the logarithm of a slope, inverting the weights the method assigns to the two quantities. The spelled-out names in the same list (“the onset rate (OR)”, “the level difference (LD)”) and the units given for each (“dB/s” for r, “dB” for d) make the intended reading unambiguous.
• Evidence: side-by-side reading of 3.4, 3.5 and the Clause 5 symbol list; the units printed with each symbol contradict the clause numbers printed with them.
• Library behaviour: implements the spelled-out reading, weighting the onset rate by 3 and the level difference by 2 (predicted_prominence in impulse_prominence.py), which is also the NT ACOU 112:2002 form the PAS carries over.
• Status: unreported.

ISO 9613-2:1996, Table 2 (15 °C / 80 % / 1 kHz cell)

• Location: Table 2, “Atmospheric attenuation coefficient α for octave bands of noise”, row 15 °C / 80 % relative humidity, column 1 kHz.
• The print: α = 4,1 dB/km.
• The problem: Table 2 is a rounded extract of ISO 9613-1, to which the clause itself defers (“For values of α at atmospheric conditions not covered in table 2, see ISO 9613-1”). Evaluating the ISO 9613-1 pure-tone formula at 1 kHz, 15 °C, 80 % RH and 101,325 kPa gives 4,1511 dB/km, which rounds to 4,2, not the printed 4,1. The neighbouring cells of the same row round correctly (2 kHz: 8,338 -> printed 8,3; 4 kHz: 23,86 -> 23,7 at the exact band centre), as do the 1 kHz cells of the other rows (15 °C / 50 %: 4,164 -> printed 4,2), so the defect is confined to this cell.
• Evidence: independent evaluation of the ISO 9613-1 coefficient at both the nominal and the exact band-centre frequency (4,1511 dB/km either way, 1 kHz being both).
• Library behaviour: unaffected. The library never reads Table 2: it computes A_atm from the ISO 9613-1 formula directly (air_absorption.py), so it yields 4,15 dB/km for this condition.
• Status: unreported.

NORAH2 rotorcraft guidance SC01.D1.5d (EASA.2020.FC.06), Eq. (27)

• Location: section A.4.2, Eq. (27) (atmospheric absorption coefficient).
• The print: the coefficient 6,6928·10⁻⁶ is paired with the relaxation frequency frO = 630,7 Hz.
• The problem: evaluated as printed, the equation yields nonsense (14,3 dB/km at 500 Hz against the guidance’s own Table 4 value of 3,1). The physically correct pairing (6,6928·10⁻⁶ with the oxygen relaxation frequency, about 75 692 Hz at the reference conditions, and 1,3415·10⁻⁶ with 630,7 Hz) reproduces Table 4 and the ISO 9613-1 pure-tone coefficient to 0,02 dB/km.
• Evidence: numeric evaluation of both pairings against Table 4.
• Library behaviour: implements the correct pairing; the module docstring carries a defensive note so the misprint is not transcribed as a “fix”.
• Status: unreported.

NORAH2 rotorcraft guidance SC01.D1.5d (EASA.2020.FC.06), Eq. (21)

• Location: section A.3.3, Eq. (21) (flight path angle).
• The print: γ = acos(ΔZ/ΔS).
• The problem: the arccosine of the climb-to-path ratio returns the complement of the path angle (90° in level flight, where γ must be 0°) and contradicts the guidance’s own use of γ as the climb/descent angle throughout section A.3. ECAC Doc 32, 1st ed., Eq. (10) prints the correct form, γ = atan(ΔZ/ΔS) with the horizontal ΔS of its Eq. (8).
• Evidence: evaluation in level flight; cross-check against Doc 32 Eq. (10) and against the NORAH2 prototype input files, whose Vang columns are climb/descent angles (0° in level segments).
• Library behaviour: flight_path_kinematics implements the Doc 32 atan form; the result docstring carries the defensive note.
• Status: unreported.

NORAH2 rotorcraft guidance SC01.D1.5d (EASA.2020.FC.06), §A.3.1 triangulation

• Location: section A.3.1, steps 2 to 4 (flight-condition interpolation), against the triangulation lookup tables shipped with the NORAH2 database (*_triangulation.int).
• The print: steps 2 and 3 normalise the database conditions (spans, with F_fc = 2 on the path angle) and step 4 computes “the Delaunay triangulation for the database flight conditions γ̄_j and V̄_j”, i.e. of the normalised points, offering a lookup table as an equivalent.
• The problem: the lookup tables shipped with the database (which the guidance says are part of the hemisphere data and should not be edited) are the Delaunay triangulation of the raw (V, γ) conditions, not of the normalised ones: for the R22 set, 14 of the 27 shipped triangles differ from the Delaunay triangulation of the normalised conditions. A Delaunay triangulation is not invariant under the anisotropic normalisation, so the two prescriptions select different enveloping triangles for part of the envelope. The distance weights of Eq. (7)/(8) do use the normalised coordinates in the prototype (verified against its blended outputs).
• Evidence: recomputation of both triangulations for the R22 database; bin-for-bin reproduction of the prototype’s per-step hemisphere selection with the shipped tables, and of its blended levels with normalised-space weights, to 0,05 dB.
• Library behaviour: flight_condition_weights follows the printed method (Delaunay of the normalised conditions) by default and accepts the database lookup table via triangles, which reproduces the reference implementation exactly.
• Status: unreported.

NORAH2 rotorcraft guidance SC01.D1.5d (EASA.2020.FC.06), Eq. (46)

• Location: section A.4.5, Eq. (46) (source-side ground effect weighted by diffraction).
• The print: the weighting exponent reads (ΔL_g,s′ − ΔL_d,s)/20.
• The problem: no term ΔL_g,s′ exists; the prose directly below the equation defines ΔL_d,s′ as “the attenuation due to the diffraction between the image source S′ and R”, the receiver-side companion Eq. (47) prints the parallel term correctly as ΔL_d,r′, and the CNOSSOS-EU method the section is based on writes Δ_ground(S,O) with Δ_dif(S′,R) in that position. The subscript g is a misprint for d.
• Evidence: internal consistency of the section (its own prose and Eq. (47)) and the CNOSSOS-EU source of the equations.
• Library behaviour: implements the image-source diffraction term ΔL_d,s′ as defined by the prose.
• Status: unreported.

NORAH2 rotorcraft guidance SC01.D1.5d (EASA.2020.FC.06), §A.4.5 cross-references

• Location: section A.4.5, the definitions under Eq. (46) and Eq. (47).
• The print: ΔL_d,s′, ΔL_d,s and ΔL_d,r′ are said to be “calculated as per eq. 44” (four occurrences: two under Eq. (46) and two under Eq. (47)).
• The problem: Eq. (44) is the multiple-diffraction coefficient C″; the attenuation due to diffraction is Eq. (42). The three cross-references point at the auxiliary coefficient instead of the formula they describe.
• Evidence: the terms are attenuations in dB, which only Eq. (42) produces; Eq. (44) is a dimensionless coefficient consumed by Eq. (42).
• Library behaviour: evaluates the image-path and direct diffraction terms with Eq. (42), using Eq. (44) for C″ inside it.
• Status: unreported.

RANDI 3.1 Physics Description (NRL, Breeding et al.), Table 2

• Location: Table 2 (representative ship source levels).
• The print: two cells deviate from the report’s own Eqs. (2) to (5) evaluated with the Table 1 average lengths and speeds: the Merchant value at 25 Hz (about 3 dB high) and the Tanker value at 300 Hz (about 1 dB low). The Fishing Vessel row is not reproducible from the Table 1 averages at all (a constant offset of about 3,8 dB suggests different assumed inputs).
• The problem: the report does not state the exact inputs used for Table 2, and two cells contradict its own equations while every Large Tanker and Super Tanker cell agrees to 0,06 dB.
• Evidence: recomputation of all 25 cells from Eqs. (2) to (5).
• Library behaviour: the regression test pins the reproducible rows and excludes the contradicting cells with the rationale in the test.
• Status: unreported (technical report rather than a standard).

Osses, García & Kohlrausch (2016), fluctuation-strength model, Eq. (3)

• Location: Eq. (3), the critical-band-rate (Bark) transformation of the excitation-pattern front-end.
• The print: z(f) = 13·arctan(0,76·10⁻⁴·f) + 3,5·arctan((f/7500)²).
• The problem: the first coefficient is the Zwicker-Terhardt 0,76·10⁻³ with the exponent misprinted. The paper’s own anchors disprove the print: it states 0,5 Bark = 50 Hz and 23,5 Bark = 13,2 kHz (section 2.1.2) and 15 Bark = 2,7 kHz (section 3.1), all of which require 10⁻³. With 10⁻⁴, z(1 kHz) = 1,05 instead of 8,51 Bark and the model’s 47 filter centres would span 491 Hz to 20 kHz instead of 50 Hz to 13,2 kHz.
• Evidence: evaluation of Eq. (3) under both exponents against the paper’s printed Bark/frequency anchors.
• Library behaviour: implements 0,76·10⁻³ with a note at the formula; the carrier-frequency sweep test would catch a regression to the printed value (fluctuation_strength.py).
• Status: unreported (conference paper rather than a standard).

Medwin & Clay, Fundamentals of Acoustical Oceanography (1998), Eq. 3.4.29

• Location: the Francois-Garrison boric-acid term as transcribed by the textbook (Eq. 3.4.29).
• The print: the boric-acid factor is printed as A1 = (8,68/c)·10^(0,78 pH − 5).
• The problem: the original paper (Francois & Garrison 1982, JASA 72, Part II, Eq. (10) and Fig. 7) prints 8,86; the digits are transposed. Only 8,86 reproduces the paper’s own Table IV: with 8,68 the boric-dominated cells at 0,6 to 30 kHz sit up to 1,7 % below the printed totals (worst relative case 2 kHz, 10 °C, S = 35: 0,1209 vs the printed 0,123 dB/km).
• Evidence: recomputation of all sampled Table IV cells under both coefficients against the paper’s printed values.
• Library behaviour: implements the paper’s 8,86 with a defensive note; the pinned Table IV set includes the boric-dominated rows.
• Status: unreported (textbook rather than a standard).

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Maa (1998), “Potential of microperforated panel absorber”, JASA 104(5), Eq. (5b)

• Location: Eq. (5b), the mass-reactance coefficient of the microperforated panel, printed as k_m = 1 + [1 + k²/2]^(−1/2) + 0,85 d/t.
• The print: the first bracket term reads (1 + k²/2)^(−1/2).
• The problem: the same paper’s Eq. (4), from which (5b) is factored, prints the term as (3² + k²/2)^(−1/2), and only that form reproduces the Crandall low-k limit Z1 → (4/3)·jωρ0t of the paper’s own Eq. (3a): at k → 0 the printed (5b) gives an internal mass factor of 2 instead of 4/3. The paper’s own Fig. 1 confirms it: with 0,85·d/t = 0,85 the plotted k_m starts near 2,2 (= 4/3 + 0,85) at k = 0,1, not at 2,85.
• Evidence: recomputation of both bracket variants against Eq. (4), Eq. (3a) and the Fig. 1 curve; the exact Bessel solution of Eq. (2) agrees with Eq. (4) within Maa’s stated ~6 % only with the 3² form (the 1 form errs by >30 % at low k).
• Library behaviour: implements the exact Eq. (2) (no approximation), so the misprint does not enter the code; the regression test test_maa_exact_vs_wide_range_approximation pins the exact solution to the corrected Eq. (4) form.
• Status: unreported (journal paper; the correct form appears in Maa’s earlier 1975/1987 papers and in secondary literature).

Jiménez, Groby, Pagneux & Romero-García (2017), Appl. Sci. 7(6), 618, Eqs. (7)-(8)

• Location: Eqs. (7) and (8), the rectangular-duct visco-thermal effective density and bulk modulus (Stinson’s series, used for the square necks and cavities of the slit + Helmholtz-resonator absorber).
• The print: the leading normalising constant of both series is 4: ρ_eff = −ρ0·a²b²/(4·G_ρ²·Σ) and the matching 4·(γ−1)·G_κ²/(a²b²) factor inside κ_eff.
• The problem: the correct constant is 64 (a factor-16 error). Only 64 reproduces the exact limits of the model: as the boundary layers vanish ρ_eff → ρ0 and κ_eff → κ0 (the printed 4 gives 16·ρ0), and at DC the square duct’s jω·ρ_eff tends to the exact Shah-London Poiseuille flow resistivity: the series value a⁶/(64·S0) = 28,4542 matches fRe/2 = 28,455 (in units of η/a²), where S0 is the double transverse-mode sum at G = 0; the printed 4 gives sixteen times that.
• Evidence: evaluation of both constants against the boundary-layer-free limits and the Shah-London exact square-duct value; the wide-duct limit of the series also only matches the papers’ own slit model (Eq. (6)) with 64.
• Library behaviour: implements 64 with a docstring note; the limits are pinned in tests/materials/test_slow_sound_absorber.py and the conformance check “Poiseuille limit (Stinson 1991)”.
• Status: unreported (journal paper rather than a standard).

Jiménez et al. (2017), Appl. Sci. 7(6), 618 / Sci. Rep. 7, 5389, slit-radiation term

• Location: Appl. Sci. Eq. (3), the characteristic radiation impedance of the slits, and the identical Methods reprint in the metadiffusers paper (Sci. Rep. 7, 5389, Eq. (5)).
• The print: Z_Δl_slit = −iω·Δl_slit·ρ0/(φt·S0).
• The problem: the term models the added radiation mass of the slit mouth, but the printed −iω prefactor is an opposite-time-convention (e^{−iωt}) expression inconsistent with the papers’ otherwise e^{+iωt} transfer-matrix chain (the +i off-diagonal slit matrices of Appl. Sci. Eq. (2) and the −i cotangent-type resonator impedance). Transcribed literally into that chain, the correction raises the slit-panel resonance where an added mass must lower it: for a 1 mm slit with a 30 mm lattice step and 50 mm period the absorption peak moves from 378,6 Hz to 386,8 Hz as printed, against 370,8 Hz with the mass sign. The neck end corrections of the same model behave correctly (they lower the resonator resonance).
• Evidence: numerical evaluation of both signs of the correction against the uncorrected panel; the direction of the neck end corrections of the same papers as the consistent control.
• Library behaviour: uses the added-mass sign (+jω in the e^{+jωt} convention of the library), conjugating the printed term exactly as it conjugates the papers’ Stinson duct series; direction and peak are pinned by test_slit_radiation_correction_lowers_resonance in tests/materials/test_slow_sound_absorber.py.
• Status: unreported (journal papers rather than standards).

Attenborough & Van Renterghem, Predicting Outdoor Sound 2e (2021), Table 5.1

• Location: Table 5.1, “Coefficient and exponent values in the Delany and Bazley, Miki and modified Miki models”, row “Miki [6,7]”, coefficient r.
• The print: r = 0,0109.
• The problem: the original source (Miki 1990, J. Acoust. Soc. Jpn (E) 11(1), Eq. (34)) prints beta(f) = (ω/c0)[1 + 0,109·(f/σ)^(−0,618)]; the table drops a digit. With 0,0109 the real part of the Miki wavenumber at f/σ = 0,01 is 1,19 instead of 2,89, inconsistent with the same table’s Delany-Bazley row (2,79 via ρ0 = 1,2) and with the “modified Miki” row the book itself derives from it.
• Evidence: digit check against the original Miki (1990) paper (Eqs. (30)–(34)) and cross-computation of both variants at the fit-range edge.
• Library behaviour: implements Miki’s original 0,109; the digitization point f/σ = 0,1 is pinned in tests/reference_data.py and in the conformance check “Miki 1990 Eqs. (30)-(34)”.
• Status: unreported (textbook rather than a standard).

Attenborough & Van Renterghem, Predicting Outdoor Sound 2e (2021), Eq. (5.13)

• Location: Eq. (5.13), the Johnson-Champoux-Allard bulk complex density, with G(Λ) = sqrt(1 − 4iTηρ0ω/(R_S²Λ²Ω²)).
• The print: the tortuosity T appears to the first power inside G(Λ).
• The problem: Johnson et al. (1987) and the standard JCA formulation (Cox & D’Antonio 3e Eq. (6.19); Allard & Atalla) carry T² = α∞² there. The first-power print breaks the high-frequency asymptote that defines the viscous characteristic length: with T² the density tends to (Tρ0/Ω)(1 + (1 − j)δ_v/Λ) with δ_v = sqrt(2η/ρ0ω), while the printed form tends to a δ_v/(Λ·sqrt(T)) correction, which for T = 2 means an error of 29 % in the boundary-layer term for the same Λ.
• Evidence: asymptotic expansion of both variants against the Johnson et al. definition of Λ and against Cox & D’Antonio Eq. (6.19); the library’s high-frequency JCA test pins the T² behaviour.
• Library behaviour: implements the standard T² form (Cox & D’Antonio Eq. (6.19)); the asymptote is pinned in test_high_frequency_density_asymptote.
• Status: unreported (textbook rather than a standard).

Bies, Hansen & Howard, Engineering Noise Control 5e (2017), Eq. (8.141)

• Location: Section 8.9.1, Eq. (8.141) (printed p. 461), the transmission loss of a muffler from the elements of its total four-pole matrix.
• The print: TL = 10 lg[ ((1+Mₙ)/(1+M₁))² · ¼ · |(Z_A1/Z_An)·T11 + T12/Z_An + Z_A1·T21 + (Z_An/Z_A1)·T22|² ], i.e. with the impedance ratio Z_A1/Z_An weighting T11 and its inverse weighting T22.
• The problem: the source the equation itself cites (Munjal, Acoustics of Ducts and Mufflers 2e, Eq. (3.27), p. 105) carries the overall prefactor Z_An/Z_A1 (equivalently √(S₁/Sₙ) inside a 20 lg form) with T11 unweighted and Z_A1/Z_An on T22. As printed, Eq. (8.141) fails the sudden-expansion limit: a zero-length element (T = I) between S₁ = 0,01 m² and Sₙ = 0,02 m² is a sudden area expansion with the classic TL = 10 lg[(1+m)²/(4m)] = 0,512 dB (m = Sₙ/S₁ = 2), but the printed equation gives ¼·(Z_A1/Z_An + Z_An/Z_A1)² = 1,938 dB. Reading the ratios as an overall Z_A1/Z_An prefactor instead is also wrong: it gives 6,532 dB on the same oracle and violates reciprocity (11,34 vs −0,70 dB for an expansion chamber between unequal pipes; a negative TL for a passive element). The misprint is invisible whenever the inlet and outlet areas are equal, where every variant reduces to Eq. (8.148).
• Evidence: numeric evaluation of the zero-length identity element and of an unequal-port expansion chamber under the printed form, the inverted prefactor and Munjal Eq. (3.27); only Munjal’s form reproduces the sudden-expansion classic (0,512 dB, both directions) and is reciprocal.
• Library behaviour: transmission_loss in silencers.py implements Munjal Eq. (3.27), with the sudden-expansion limit and TL reciprocity pinned by regression tests (tests/noise_control/test_silencers.py) and a defensive note at the formula.
• Status: unreported (textbook rather than a standard).

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Related source properties that are not errata

Recorded here to prevent future “fixes” that would break agreement with the published sources:

• Francois-Garrison pure-water term: the two published A3 cubics do not meet exactly at the 20 °C switch (a step of 1·10⁻⁷·f² dB/km, 0,1 dB/km at 1 MHz). Inherent in the published coefficients.
• Ainslie-McColm simplification: the paper’s “within 10 % of Francois-Garrison” claim is marginally exceeded at the extreme corners of its stated domain (10,4 % at −6 °C / 1 MHz; 12,3 % at 7 km depth). A property of the published fit; both transcriptions verified digit-for-digit.
• ICAO Annex 16 EPNL constant: the Annex’s rounded constant 13 for uniform 0,5 s records differs from the exact −10·lg(T0) form by 0,0103 dB; the library uses the exact form, which the ETM’s integrated reference reproduces to five decimals.