Source: https://jmrplens.github.io/phonometry/materials/resilient/ # Resilient layers A floating floor is a mass-spring system: the screed is the mass, the resilient layer is the spring, and the impact improvement the pair buys begins above the resonance they set. That resonance is fixed by the mass per unit area m' of the slab, in kg/m², and by the **dynamic stiffness per unit area** s' of the layer, in MN/m³ — the dynamic force per unit area divided by the change in thickness it produces. A 120 kg/m² screed on a 10 MN/m³ layer resonates near 46 Hz; halving the stiffness moves that down by a factor of the square root of two, and everything the floor achieves in the rated bands follows from where the resonance sits. This is why s' is the one number a resilient-layer datasheet must carry, and why it is a *dynamic* stiffness: a static compression test describes neither the audio frequency range nor the working preload. [Dynamic stiffness of resilient materials (EN 29052-1)](https://jmrplens.github.io/phonometry/materials/dynamic-stiffness/) is the measurement that produces it. A 200 mm × 200 mm specimen carries an 8 kg load plate — 200 kg/m² in total, which reproduces the roughly 2 kPa static preload of a real floating floor — and a vertical exciter with an accelerometer gives the fundamental resonance of the plate-on-specimen system, from which the apparent stiffness follows directly. For an air-permeable material the pore air is a second spring in parallel with the frame, and the standard adds it back through an enclosed-gas term that depends on the loaded thickness: the installed stiffness therefore depends on how the layer will be sealed and on its lateral airflow resistivity, which is what the clause 8.2 regimes decide. The guide chains all of it and renders the clause 9 test-report fiche. Two inputs come from outside this subsection. The resonant frequency has to be extrapolated to zero force amplitude by the clause 7 procedure, and the airflow resistivity is measured by ISO 9053 in [Airflow Resistance](https://jmrplens.github.io/phonometry/absorbers/airflow-resistance/) — note that ISO 9053 reports it in Pa·s/m² while this page's argument is in kPa·s/m². What the design side does with s' is [Predicting resilient-layer performance](https://jmrplens.github.io/phonometry/buildings/design/resilient-layers/), which turns it into the floating-floor improvement and the ISO 12354-1 Annex D lining rating. ## Pages in this section - [Dynamic stiffness of resilient materials (EN 29052-1)](https://jmrplens.github.io/phonometry/materials/dynamic-stiffness/): the load-plate resonance method, the apparent stiffness it yields, the enclosed-gas term for air-permeable layers, the airflow-resistivity regimes of clause 8.2 and the clause 9 test-report fiche. ## See also Pages elsewhere on the site that this section leans on: - [Airflow Resistance](https://jmrplens.github.io/phonometry/absorbers/airflow-resistance/): the ISO 9053 measurement of the lateral resistivity the regime rule needs. - [Predicting resilient-layer performance](https://jmrplens.github.io/phonometry/buildings/design/resilient-layers/): the consumer, where s' becomes a floating-floor improvement. ## What this section does not cover The measurement starts one step after the signal. Clause 7's extraction of the resonant frequency from the raw excitation-response record — by sinusoidal, white-noise or pulse excitation — and its extrapolation to zero force amplitude are **not implemented**: pass a resonant frequency that has already been extrapolated. The lateral airflow resistivity is an input, not a measurement. Clause 6's specimen-selection requirement of at least three 200 mm × 200 mm specimens is not enforced, so nothing here objects if you characterise a material from one. And the layer's other properties — creep under long-term load, compressive strength, thermal performance — are outside the standard and outside the library.