Source: https://jmrplens.github.io/phonometry/buildings/design/impact-improvement/ # Floor-Covering Impact Improvement (ISO 16251-1) A soft floor covering does not block airborne sound; it cushions footsteps. What it improves is the impact level of the floor underneath, and measuring that improvement in a full ISO 10140 transmission suite is out of proportion to a square metre of carpet. ISO 16251-1 therefore shrinks the laboratory to a small heavyweight mock-up: a softly supported concrete plate, a standard tapping machine and an accelerometer underneath. This guide covers the mock-up measurement of the improvement $\Delta L$ and its weighted $\Delta L_\mathrm{w}$ against the ISO 717-2 reference floor, the accredited fiche, and the ISO 12354-2 engineering estimate that predicts a floating floor's improvement from the dynamic stiffness of its resilient layer. The full-size laboratory chain lives in [Laboratory Insulation Measurement](https://jmrplens.github.io/phonometry/buildings/insulation/insulation-lab/); the $s'$ measurement behind the estimate is the subject of [Dynamic stiffness of resilient materials (EN 29052-1)](https://jmrplens.github.io/phonometry/materials/resilient/dynamic-stiffness/). ## The small-mock-up method ISO 16251-1:2014 is a laboratory method for the **improvement of impact sound insulation** $\Delta L$ of a soft, locally-reacting floor covering (carpet, PVC, linoleum). The two ISO 10140 rooms are replaced by a small softly-supported concrete plate; a standard tapping machine excites it and the structure-borne **acceleration level** on the underside is measured with and without the covering. For locally-reacting coverings that acceleration-level difference equals the ISO 10140 impact sound reduction. **Acceleration level (Formula (1)).** $L_a = 10\log_{10}(\langle a^2\rangle / a_0^2)$ dB, reference $a_0 = 10^{-6}\ \text{m/s}^2$. **Background correction (Formula (2))** follows the ISO 10140 three-branch rule (unchanged ≥ 15 dB; energy subtraction for 6 ≤ margin < 15 dB; the 1.3 dB limit below 6 dB, flagged as $> \Delta L$). The improvement is the position-averaged difference $\Delta L = L_0 - L_1$ (Formulae (3)/(4)); octaves follow $\Delta L_\mathrm{oct} = -10\log_{10}[\tfrac{1}{3}\sum 10^{-\Delta L_n/10}]$ (Formula (5)). **Weighted improvement.** $\Delta L_\mathrm{w}$ is the ISO 717-2 weighted reduction: the improvement is applied to the heavyweight **reference floor** $L_\mathrm{n,r,0}$ (ISO 717-2 Table 4), $L_\mathrm{n,r} = L_\mathrm{n,r,0} - \Delta L$, and $\Delta L_\mathrm{w} = 78 - L_\mathrm{n,r,w}$, computed by `weighted_impact_improvement()`, which reuses the verified ISO 717-2 rating engine. A clause 6.3 measurement spans 18 bands (100–5000 Hz, optionally extended to 50 Hz); the rating is formed on the 100–3150 Hz sub-range of whatever spectrum contains it. The statement of results (clause 8 e)) also carries the spectrum adaptation term $C_{\mathrm{I},\Delta} = C_\mathrm{I,r,0} - C_\mathrm{I,r}$ (ISO 717-2:2020 Formula (A.4)), exposed as `ci_delta` on the result and standalone as `impact_improvement_adaptation_term()`. The worked example below is a real measurement: the improvement of a textile carpet on the CSTB heavyweight mock-up, digitized from Figure 4 of Foret, Chéné and Guigou-Carter, "A comparison of the reduction of transmitted impact noise by floor coverings measured using ISO 140-8 and ISO/CD 16251-1" (Forum Acusticum 2011, Aalborg). Its published ISO 16251-1 weighted improvement is $\Delta L_\mathrm{w} = 29$ dB, reproduced exactly by the rating engine.

Show the code for this figure

```python import matplotlib.pyplot as plt import numpy as np from phonometry import building freqs = [100, 125, 160, 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500, 3150] bare = np.full(16, 78.0) # bare-plate acceleration level # A real textile carpet measured on the CSTB mock-up (Foret et al. 2011, Fig. 4). covering = bare - np.array([5, 8, 10, 14, 18, 23, 30, 31, 39, 49, 53, 57, 60, 67, 68, 71]) res = building.impact_improvement(bare, covering, freqs) print(res.delta_lw) # weighted improvement delta-Lw = 29 dB (ISO 717-2) res.plot() plt.show() ```

```python from phonometry import building # delta-Lw straight from an improvement spectrum (16 one-third-octave bands): delta_l = [5, 8, 10, 14, 18, 23, 30, 31, 39, 49, 53, 57, 60, 67, 68, 71] print(building.weighted_impact_improvement(delta_l)) # 29 dB (carpet) # From the measured bare/covered acceleration levels, with a background trace: freqs = [100, 125, 160, 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500, 3150] bare_levels = [72, 73, 74, 74, 75, 75, 76, 76, 77, 77, 78, 78, 79, 79, 80, 80] covered_levels = [b - d for b, d in zip(bare_levels, delta_l)] bg = [40.0] * 16 res = building.impact_improvement(bare_levels, covered_levels, freqs, background=bg) res.improvement # delta-L per band res.delta_lw # weighted single number (rated on the 100-3150 Hz sub-range) res.ci_delta # spectrum adaptation term CI,delta (Formula (A.4)) res.limited # bands at the 1.3 dB limit of measurement (> delta-L) res.octave_bands() # (octave freqs, delta-L_oct) via Formula (5) res.plot() # the delta-L(f) improvement spectrum above (needs matplotlib) ``` ## ISO 16251-1 impact-improvement report (`.report()`) `FloorCoveringImprovementResult.report()` writes a one-page accredited impact-improvement fiche: the ISO 16251-1 basis line, a metadata header, the per-band table (frequency and $\Delta L$, bands at the 1.3 dB limit prefixed `>`) beside the $\Delta L(f)$ improvement curve, the boxed single-number $\Delta L_\mathrm{w}\ (C_{\mathrm{I},\Delta})$ (the ISO 16251-1 Clause 8 e) statement of results, rated per ISO 717-2) and a footer. The applicable `ReportMetadata` fields are `specimen` (the floor covering under test), `client`, `manufacturer`, `mounting`, `mass_per_area`, `test_room`, `test_date`, `temperature`, `pressure`, `measurement_standard`, `laboratory`, `operator`, `report_id`, `notes` and `requirement` (a higher weighted improvement is better, so the verdict passes at or above it). The bare reference floor is the standardised heavyweight floor of ISO 717-2:2020 Table 4, fixed by the standard. `verbose=True` adds the reference-floor-with-covering column $L_\mathrm{n,r} = L_\mathrm{n,r,0} - \Delta L$, the derivation basis of $\Delta L_\mathrm{w}$. ```python from phonometry import building, ReportMetadata freqs = [100, 125, 160, 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500, 3150] delta_l = [5, 8, 10, 14, 18, 23, 30, 31, 39, 49, 53, 57, 60, 67, 68, 71] bare = [78.0] * 16 res = building.impact_improvement(bare, [b - d for b, d in zip(bare, delta_l)], freqs) res.report("dLw.pdf", metadata=ReportMetadata( specimen="Textile floor covering (carpet), laid loose", measurement_standard="ISO 16251-1", requirement=20.0)) # delta-Lw (CI,delta) = 29 (-13) dB ``` A rendered example fiche, regenerated with `make reports`, is kept in the repository. Click the preview to open the PDF: [](https://raw.githubusercontent.com/jmrplens/phonometry/main/.github/reports/iso16251_floor_covering_example.pdf) ## From dynamic stiffness to the improvement: the ISO 12354-2 estimate The mock-up measures a *covering* that exists; a **floating floor** (a screed poured on a resilient layer) is designed the other way round, from two numbers known at the drawing stage: the mass per unit area $m'$ of the slab and the dynamic stiffness per unit area $s'$ of the resilient layer, measured per EN 29052-1 as in the [dynamic-stiffness guide](https://jmrplens.github.io/phonometry/materials/resilient/dynamic-stiffness/). Together they set the mass-spring resonance of the system (ISO 12354-2:2017, Annex C, Formula (C.2)): $$ f_0 = 160 \sqrt{\frac{s'}{m'}}\ \text{Hz} \qquad (s'\ \text{in MN/m}^3,\ m'\ \text{in kg/m}^2), $$ where 160 is the rounded $1000/2\pi$; `materials.natural_frequency` computes the exact $\tfrac{1}{2\pi}\sqrt{s'/m'}$ form. Above the resonance the slab decouples from the structural floor and Annex C estimates the improvement as a straight slope per Formula (C.1), with the steeper Formula (C.3) for constructions whose higher internal losses follow the infinite-plate theory: $$ \Delta L = 30 \log_{10} \frac{f}{f_0}\ \text{dB (sand/cement, calcium-sulfate screeds)}, \qquad \Delta L = 40 \log_{10} \frac{f}{f_0}\ \text{dB (asphalt, dry screeds)}. $$ ```python import numpy as np from phonometry import building, materials # The ISO 12354-2:2017 Annex G worked floor: a 73.5 kg/m2 screed on a resilient # layer with s' = 8 MN/m3. f0 = 160.0 * np.sqrt(8.0 / 73.5) # Formula (C.2) print(round(f0, 1)) # 52.8 Hz print(round(float(materials.natural_frequency(8.0e6, 73.5)), 1)) # 52.5 exact 1/(2 pi) form # delta-L = 30 lg(f/f0) above the resonance (Formula (C.1)); build the # one-third-octave spectrum and rate it with the ISO 717-2 engine. freqs = np.array([100, 125, 160, 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500, 3150], dtype=float) delta_l = 30.0 * np.log10(freqs / f0) print(building.weighted_impact_improvement(delta_l)) # 32 dB # The one-line estimate of Formula (C.4) lands right beside it: print(round(13.0 * np.log10(73.5) - 14.2 * np.log10(8.0) + 20.8, 1)) # 32.2 dB ``` The closed-form weighted estimate of Formula (C.4), $\Delta L_\mathrm{w} = 13\log_{10} m' - 14{,}2\log_{10} s' + 20{,}8$ dB, condenses the same physics into one line: heavier slabs and softer layers rate better. Both estimates are design aids kept deliberately on the safe side (the 30 lg slope undercuts the 40 lg infinite-plate theory where experimental data say real screeds fall short); once a specimen exists, the measured mock-up of this page, or the full ISO 10140-3 floor, is the reference, and the [EN 12354-2 prediction](https://jmrplens.github.io/phonometry/buildings/design/insulation-prediction/) consumes whichever $\Delta L_\mathrm{w}$ you have. ## References - Vigran, T. E. (2008). *Building acoustics*. CRC Press. ISBN 978-0-415-42853-8. [doi:10.1201/9781482266016](https://doi.org/10.1201/9781482266016). The transmission theory of floors and floating floors that the improvement quantifies. - Foret, R., Chéné, J.-B., & Guigou-Carter, C. (2011). A comparison of the reduction of transmitted impact noise by floor coverings measured using ISO 140-8 and ISO/CD 16251-1. *Forum Acusticum 2011, Aalborg* (CSTB). The measured textile-carpet improvement spectrum used as the worked example on this page ($\Delta L_\mathrm{w} = 29$ dB); the per-band $\Delta L$ was digitized from its Figure 4. - International Organization for Standardization. (2014). *Acoustics — Laboratory measurement of the reduction of transmitted impact noise by floor coverings on a small floor mock-up — Part 1: Heavyweight compact floor* (ISO 16251-1:2014). [iso.org catalogue](https://www.iso.org/standard/56017.html). The small-mock-up method this page implements. - International Organization for Standardization. (2020). *Acoustics — Rating of sound insulation in buildings and of building elements — Part 2: Impact sound insulation* (ISO 717-2:2020). [iso.org catalogue](https://www.iso.org/standard/69867.html). The reference floor $L_\mathrm{n,r,0}$ (Table 4) and the rating engine behind $\Delta L_\mathrm{w}$, with the Formula (A.4) adaptation term $C_{\mathrm{I},\Delta}$. - International Organization for Standardization. (2017). *Building acoustics — Estimation of acoustic performance of buildings from the performance of elements — Part 2: Impact sound insulation between rooms* (ISO 12354-2:2017). [iso.org catalogue](https://www.iso.org/standard/70239.html). The informative Annex C floating-floor estimate reproduced above (Formulae C.1 to C.4) and the worked floor of Annex G. ## Standards ISO 16251-1:2014, which specifies the small-mock-up laboratory method for the impact-sound improvement $\Delta L$ of floor coverings; ISO 717-2:2020, which supplies the reference floor, the $\Delta L_\mathrm{w}$ rating and the $C_{\mathrm{I},\Delta}$ adaptation term; and ISO 12354-2:2017 Annex C (informative), whose floating-floor estimate this page reproduces from the EN 29052-1 dynamic stiffness, with the worked floor of its Annex G (context for design, not a measurement). **Not covered.** The mock-up facility itself — the plate dimensions, the resilient supports, the tapping-machine positions of Clause 5 — is not checked: the functions consume measured acceleration levels wherever they came from. The ISO 12354-2:2017 Annex C floating-floor formulae are quoted here as design aids and evaluated inline; the helpers that wrap them, the tapping-machine force model behind a soft covering's improvement and the **ISO 12354-1** Annex D rating of a wall lining belong to [Predicting resilient-layer performance](https://jmrplens.github.io/phonometry/buildings/design/resilient-layers/). The superseded full-size ISO 140-8 method survives only as the comparison axis of the Foret et al. (2011) worked example. ## See also - [Laboratory Insulation Measurement](https://jmrplens.github.io/phonometry/buildings/insulation/insulation-lab/): the ISO 10140 suite this mock-up replaces for soft coverings, and the full-size ISO 10140-3 improvement measurement. - [Dynamic stiffness of resilient materials (EN 29052-1)](https://jmrplens.github.io/phonometry/materials/resilient/dynamic-stiffness/): the $s'$ measurement that feeds the floating-floor estimate. - [Predicting Resilient-Layer Performance](https://jmrplens.github.io/phonometry/buildings/design/resilient-layers/): the prediction counterpart of this page, from the tapping-machine force model to floating floors and wall linings. - [Predicting Sound Insulation (EN 12354)](https://jmrplens.github.io/phonometry/buildings/design/insulation-prediction/): the impact model whose Formula (21) consumes $\Delta L_\mathrm{w}$. - [Insulation Ratings (ISO 717)](https://jmrplens.github.io/phonometry/buildings/insulation/insulation-ratings/): the reference-curve engine behind the weighted improvement. - API reference: [`building.measurement.floor_covering_improvement`](https://jmrplens.github.io/phonometry/reference/api/building/floor-covering-improvement/).