Source: https://jmrplens.github.io/phonometry/buildings/insulation/heavy-impact-sources/ # Heavy and Soft Impact Sources (ISO 16283-2) The ISO tapping machine is a *light* impact source. Its five 500 g hammers fall 40 mm and produce a hard, quasi-stationary excitation whose energy sits well above 100 Hz, which is exactly where a bare concrete slab already performs well. The impacts people actually complain about, a child jumping off a chair or an adult walking barefoot on a timber floor, are slow, soft and low-frequency, and the tapping machine says almost nothing about them. The **standard heavy impact sources** were introduced to close that gap: a hollow silicone **rubber ball** dropped from 1 m, and the **bang machine**, a car tyre dropped from 85 cm. This guide covers their normative specification, the laboratory verification of a source against it, the standardization of the maximum level in the receiving room, and the A-weighted single number. The tapping-machine chain lives in [Field Insulation Measurement (ISO 16283)](https://jmrplens.github.io/phonometry/buildings/insulation/insulation-field/) and [Laboratory Insulation Measurement](https://jmrplens.github.io/phonometry/buildings/insulation/insulation-lab/). *Left: the two source specifications are pure spectra of force, not geometry. Right: the rating adds the A-weighted band contributions in energy, so the 63 Hz band decides almost everything.* ## Both sources are specified by the energy of their force pulse A heavy source is not defined by its shape but by the **impact force exposure level** it delivers into a rigid floor (ISO 16283-2:2020 Formula (A.1) = JIS A 1418-2:2019 Formula (1)): $$ L_{F\mathrm{E}} = 10\log_{10}\!\left[\frac{1}{T_\mathrm{ref}} \int_{t_1}^{t_2}\frac{F^2(t)}{F_0^2}\,\mathrm{d}t\right]\ \text{dB re 1 N}, $$ with $F_0 = 1$ N, $T_\mathrm{ref} = 1$ s and $t_2 - t_1$ the duration of the impact. Both characteristics require a **single-peak** waveform of $20 \pm 2$ ms (JIS A 1418-2:2019 A.2 b)). The octave-band values are printed identically in ISO 16283-2:2020 Table A.1, ISO 10140-5:2010 Table F.1 and JIS A 1418-2:2019 Table A.2 for the ball; the bang machine appears only in JIS A 1418-2:2019 Table A.1. | Octave (Hz) | Rubber ball $L_{F\mathrm{E}}$ (dB re 1 N) | Bang machine $L_{F\mathrm{E}}$ (dB re 1 N) | |---|---|---| | 31.5 | 39.0 ± 1.0 | 47.0 ± 1.0 | | 63 | 31.0 ± 1.5 | 40.0 ± 1.5 | | 125 | 23.0 ± 1.5 | 22.0 ± 1.5 | | 250 | 17.0 ± 2.0 | 11.5 ± 2.0 | | 500 | 12.5 ± 2.0 | 5.5 ± 2.0 | The bang machine puts 8 dB more energy into the two lowest octaves and 7 dB less into the top one, which is why the two sources are not interchangeable and why a floor can pass one and fail the other. ```python from phonometry import ( check_heavy_impact_source, heavy_impact_source_limits, heavy_impact_source_specification, impact_force_exposure_level, ) spec = heavy_impact_source_specification("rubber_ball") print(spec.drop_height, spec.effective_mass) # 1.0 m, 2.5 kg print(spec.contact_time, spec.contact_time_tolerance) # 0.02 s +/- 0.002 s freqs, lower, upper = heavy_impact_source_limits("bang_machine") print(list(zip(freqs, lower, upper))[0]) # (31.5, 46.0, 48.0) # A calibration run: five measured octave-band LFE against the printed table. check = check_heavy_impact_source([39.4, 30.2, 23.6, 18.5, 12.9]) print(check.passed, list(check.within_tolerance)) check.plot() # measured LFE over the tolerance band (needs matplotlib) ``` `impact_force_exposure_level` evaluates Formula (A.1) directly from a sampled force record, which is what the JIS A 1418-2 Annex C calibration procedure measures with a force plate. The specification is stated **per octave band**, and Annex C puts the filter between the transducer and the analyser, so the record is band-filtered first and the formula is applied once per band: an unfiltered pulse returns the broadband level, which is several decibels above any single band value and must not be compared with the table above. ```python import numpy as np from phonometry import OctaveFilterBank, impact_force_exposure_level fs = 48_000 t = np.arange(0.0, 0.020, 1.0 / fs) # the 20 ms contact time force = 1500.0 * np.sin(np.pi * t / 0.020) # a single-peak half-sine pulse # Broadband, i.e. the whole pulse energy: 10 lg(Fp^2 t / 2) = 43.5 dB. # Not a band value, and not comparable with the table above. print(round(impact_force_exposure_level(force, fs), 2)) # The five octave-band values the specification is actually written in. bank = OctaveFilterBank(fs, fraction=1, limits=[31.5, 500.0]) _, freqs, bands = bank.filter(force, sigbands=True, calculate_level=False) lfe = [impact_force_exposure_level(b, fs) for b in bands] print([round(v, 1) for v in lfe]) # [-1.4, 14.0, 22.1, 20.2, 17.1] # Those five go to the conformance check; this synthetic half-sine is not a # rubber ball, so it does not conform: # check_heavy_impact_source(lfe).passed -> False ``` The construction examples the two standards give are informative, not normative: a hollow silicone ball of 180 mm outer diameter with a 30 mm wall, effective mass $(2.5 \pm 0.1)$ kg and coefficient of restitution $0.8 \pm 0.1$, dropped from $(100 \pm 1)$ cm measured from the bottom of the ball; and a car tyre inflated to $(2.4 \pm 0.2)\times 10^5$ Pa with an effective mass of $(7.3 \pm 0.2)$ kg, dropped from 85 cm. ## The receiving room: a maximum level cannot be corrected like an average The rated quantity is a **maximum** of a Fast time-weighted level, not an energy average, so the usual $10\log_{10}(T/T_0)$ standardization is wrong: a Fast detector never integrates more than about 1.7 s of decay, so the correction has to saturate. ISO 16283-2:2020 (definition 3.16, Formulae (4), (5) and (6)) therefore uses $$ L'_{\mathrm{i,Fmax},V,T} = L_\mathrm{i,Fmax} + 10\log_{10}\frac{V}{V_0} - 10\log_{10}\frac{g(C)}{g(C_0)},\qquad C = \frac{T}{1{,}7275},\quad C_0 = \frac{T_0}{1{,}7275}, $$ with $T_0 = 0{,}5$ s, $V_0 = 50\ \text{m}^3$ for dwellings and, writing Formula (4) compactly, $$ g(C) = \frac{C^{1/(1-C)} - C^{-1/(1-1/C)}}{1 - 1/C}. $$ $g$ is the peak of the Fast-weighted response to an exponentially decaying burst. It has a removable singularity at $C = 1$ (i.e. $T = 1{,}7275$ s) where its value is $1/e$. When $T = T_0$ the bracket collapses to 1 and the whole correction reduces to the volume term, as it must. ```python from phonometry import ( fast_reverberation_correction, heavy_impact_octave_levels, standardized_maximum_impact_level, ) freqs = [63.0, 125.0, 250.0, 500.0] li_fmax = [65.3, 64.5, 58.0, 55.8] # energy-averaged over ball positions t = [1.43, 3.70, 3.10, 2.38] # receiving-room reverberation time res = standardized_maximum_impact_level(li_fmax, 41.4, t, frequency=freqs) print(res.volume_term) # 10 lg(41.4/50) = -0.8 dB print(fast_reverberation_correction([0.5])) # exactly 0 dB at T = T0 res.plot() # measured and standardized spectra (needs matplotlib) # One-third-octave measurements combine into octaves with Formula (20): print(heavy_impact_octave_levels([60.0] * 6)) # +10 lg 3 dB per octave ``` ## The single number is an A-weighted sum, not a shifted curve ISO 717-2:2020 Annex D is normative and does not use a reference curve at all. The rating is an energy sum of A-weighted band levels (Formula (D.1)): $$ X_\mathrm{iA,Fmax} = 10\log_{10}\!\left(\sum_j 10^{(X_{\mathrm{i,Fmax},j} + A_j)/10}\right), $$ over the one-third-octave bands 50 Hz to 630 Hz **or** the octave bands 63 Hz to 500 Hz, with the Table D.3 corrections $A_j$, rounded half-up to an integer. A one-third-octave measurement is rated in one-third octaves; the standard warns explicitly against summing thirds into octaves first, because the two routes do not give the same answer. The same formula rates all four quantities of Tables D.1 and D.2: $L_\mathrm{iA,Fmax}$, $L_{\mathrm{iA,Fmax},V,T}$, $L'_\mathrm{iA,Fmax}$ and $L'_{\mathrm{iA,Fmax},V,T}$. The worked example of Table D.4 is reproduced exactly, including the deliberately unrounded intermediate the standard prints: ```python from phonometry import a_weighted_maximum_impact_level # ISO 717-2:2020 Table D.4: a field measurement in octave bands. res = a_weighted_maximum_impact_level([65.3, 64.5, 58.0, 55.8]) print(list(res.corrected)) # 39.1, 48.3, 49.3, 52.6 dB print(res.unrounded) # 55.350667... dB print(res.rating) # 55 dB res.plot() # band levels, A-weighted contributions, rating ``` Because the A-weighting is 23 dB steeper at 63 Hz than at 500 Hz, a heavy source's rating is dominated by whichever band survives that slope. For the Table D.4 spectrum the four A-weighted contributions are 39.1, 48.3, 49.3 and 52.6 dB, so the 500 Hz band carries the most weight even though 63 Hz is the loudest band by 10 dB. ## What this guide covers **Covered.** The impact force exposure level of ISO 16283-2:2020 Formula (A.1) from a sampled force record, via `building.impact_force_exposure_level`; the printed octave-band specifications of ISO 16283-2:2020 Table A.1 / ISO 10140-5:2010 Table F.1 (rubber ball) and JIS A 1418-2:2019 Tables A.1 and A.2 (both characteristics) with their tolerances, via `building.heavy_impact_source_specification`, `building.heavy_impact_source_limits` and `building.check_heavy_impact_source`; the standardized maximum impact sound pressure level of Formulae (4), (5) and (6) and the octave synthesis of Formula (20), via `building.standardized_maximum_impact_level`, `building.fast_reverberation_correction` and `building.heavy_impact_octave_levels`; and the normative A-weighted rating of ISO 717-2:2020 Annex D with the Table D.3 corrections, via `building.a_weighted_maximum_impact_level`. **Not covered.** The field measurement procedure itself (the four or more drop positions of ISO 10140-3 Annex A, the microphone positions and the low-frequency corner procedure) is not automated: the functions consume levels that were already energy-averaged over positions. There is no prediction model that takes a floor construction to a heavy-impact level; Hopkins states plainly that the complexity of the input force and the use of a time-weighted maximum leave no simple counterpart to the tapping-machine prediction. No accredited worked example exists anywhere that carries a real floor from measured $L_\mathrm{i,Fmax}$ through to $L'_{\mathrm{iA,Fmax},V,T}$, so the standardization chain is anchored on its own $T = T_0$ identity and on a published 25-band reproduction of Formula (4). ## References - ISO 16283-2:2020, *Acoustics — Field measurement of sound insulation in buildings and of building elements — Part 2: Impact sound insulation*. Definition 3.16 and Formulae (4), (5), (6), (9), (15) and (20); Annex A.2 (rubber ball) with Table A.1 and Formula (A.1). - ISO 10140-5:2010, *Acoustics — Laboratory measurement of sound insulation of building elements — Part 5: Requirements for test facilities and equipment*. Annex F (normative): F.1 the modified tapping machine, F.2 the rubber ball with Table F.1. - ISO 10140-3:2010, Annex A (informative), *Measurement using heavy and soft impact sources*. - JIS A 1418-2:2019, *Acoustics — Measurement of floor impact sound insulation of buildings — Part 2: Method using standard heavy impact sources*. Annex A (normative) with Tables A.1 and A.2, Annex B (informative) construction examples, Annex C (informative) force calibration. - ISO 717-2:2020, *Acoustics — Rating of sound insulation in buildings and of building elements — Part 2: Impact sound insulation*. Annex D (normative), Formula (D.1), Tables D.1 to D.4. - Hopkins, C. (2007). *Sound Insulation*. Butterworth-Heinemann, Section 3.6.4. ## Standards | Standard | Scope in this guide | |---|---| | ISO 16283-2:2020 | Field measurement with the rubber ball: the source spectrum (Annex A) and the standardized maximum level (Formulae (4) to (6), (20)) | | ISO 10140-5:2010 | Laboratory requirements: Annex F, the heavy and soft impact sources | | ISO 10140-3:2010 | Laboratory measurement with heavy and soft sources (Annex A) | | JIS A 1418-2:2019 | Both impact force characteristics with their tolerances and construction examples | | ISO 717-2:2020 | Annex D, the A-weighted maximum impact sound pressure level | ## See also - [Field Insulation Measurement (ISO 16283)](https://jmrplens.github.io/phonometry/buildings/insulation/insulation-field/): the tapping-machine chain of the same standard. - [Laboratory Insulation Measurement](https://jmrplens.github.io/phonometry/buildings/insulation/insulation-lab/): the ISO 10140 laboratory suite the heavy sources extend. - [Insulation Ratings (ISO 717)](https://jmrplens.github.io/phonometry/buildings/insulation/insulation-ratings/): the reference-curve engine that rates the tapping-machine quantities. - [Floor-Covering Impact Improvement (ISO 16251-1)](https://jmrplens.github.io/phonometry/buildings/design/impact-improvement/): the improvement a soft covering gives against the light source.