Adaptive ghost indicator (impact sounds)

Professional Definition

The value added to the weighted indicator to account for the sound spectra characteristics typical of footsteps.

In acoustic engineering, this parameter is denoted by the symbol CI (according to ISO standard 717-2). It is a corrective size for the single-number weighted impact sound level indicator (Ln,w) used in the case of uncarpeted floors (e.g., wooden, concrete without coverings). This correction is essential because the standard reference curve does not always properly account for peaks in acoustic energy in the low frequency range, which are characteristic of walking (the so-called thumping noise).

Acoustics in Simple Words

Imagine that you are buying running shoes. The standard size (weighted indicator) tells you whether the shoe will fit your foot, but it doesn't tell you whether it will cushion the impact on concrete. Adaptive spectral indicator is information about this cushioning. If the floor has poor insulation in the low tone range (a dull thump when walking), the standard measurement result may suggest that it is quiet, while in reality you hear every step of your neighbor. This indicator acts as a "realism" filter, correcting the assessment to better reflect the nuisance of heavy steps on a hard floor.

Summary

The adaptive spectral indicator for impact sounds (CI) is a mathematical correction that allows for a more precise assessment of the acoustic comfort of floors. It is crucial in designing hard floors, where troublesome low frequencies dominate.