ISO 717-2 - Calculation of the Ratings of Impact Sound Insulation
Introduction
This tool applies the ISO 717-2 rating method to convert impact sound measurements into clear single-number acoustic indicators. In practice, the standard is used to rate the impact sound insulation of floors and to express the acoustic benefit of a resilient layer, floor covering, or floating floor with a simple result that is easy to compare between systems.
In AcouVApp, the first calculation mode is used to determine a weighted impact sound value for a single floor such as Lnw or L'n,w, depending on the measurement context. These values describe the impact sound performance of a floor alone.
The second calculation mode is dedicated to floor systems with an added material. It compares the impact sound spectrum of the bare support with the impact sound spectrum of the same support after adding a floor covering or resilient layer. From this comparison, the tool calculates the weighted improvement ΔLw, which represents thereduction of impact noise provided by the added layer.
How the ISO 717-2 calculation works
ISO 717-2 does not directly average the measured values. Instead, it compares the measured impact sound spectrum with a standardized reference curve. This reference curve is shifted vertically until the sum of the unfavorable deviations is as large as possible without exceeding the limit imposed by the standard. Once the correct position is found, the value of the shifted reference curve at 500 Hz becomes the weighted single-number result.
In third-octave mode, this method gives the most precise rating and is the preferred approach for laboratory and detailed product evaluation. It allows the calculation of weighted impact sound levels for a floor and also the weighted reduction in impact sound pressure level for floor coverings.
Because two floor systems may have the same weighted result while behaving differently at low or mid frequencies, ISO 717-2 also introduces the spectrum adaptation term Ci. This correction helps represent how the floor behaves with a more realistic impact sound spectrum, especially for typical walking noise.
For DeltaLw calculation, the standard proposes a method with a reference curves based on different floor types. 3 types of floor are provided in the tool : Heavy floor (ISO 10140-1) and two light floors (ISO 10140-5).
Meaning of the results displayed in the tool
The tool can display several final indicators depending on the selected workflow:
- Lnw or L'n,w: weighted impact sound level of the tested floor or assembly. Lower values indicate better impact sound insulation.
- Ci: spectrum adaptation term used together with the weighted value to provide a more representative acoustic rating.
- ΔLw: weighted reduction in impact sound pressure level obtained by adding a floor covering, underlay, or floating floor system. Higher values indicate a better acoustic improvement.
Results are usually written in a compact form such as Lnw (Ci) or L'n,w + Ci. This makes it possible to compare products quickly while still keeping useful information about the spectral behavior of the floor system.
What to enter in AcouVApp
The first tab is intended for direct ISO 717-2 rating of measured impact sound data. You paste one measured column per test, and the tool compares each column with the standard reference curve to calculate the weighted result and the associated Ci value.
The second tab is intended for floor covering performance. It expects one column for the support Ln values and one column for the support + material Ln values. The tool then calculates the improvement band by band and determines the final ΔLw according to the ISO 717-2 floor covering procedure.
Values can be pasted directly into the table columns, which makes the tool practical for laboratory data processing, product comparison, and acoustic reporting.
For other single quantities, use absorption index or acoustic insulation index modules in AcouVApp.
Outputs generated by the calculator
- Lnw (Ci) or L'n,w (Ci) for each measurement column
- ΔLw for floor covering or floating floor improvement
- Band-by-band comparison between measured values and the ISO reference curve
- Graph preview of measured and reference curves
- Real-time update of all calculated results when values are modified