Insulation rating indicator with adaptation C

Professional Definition

The sum of the weighted index of the relevant sound insulation parameter against airborne sounds and the spectral adaptation index C. NOTE - the index refers to any parameter defining insulation against airborne sounds and is denoted as “A1” in the symbol index of that parameter.

In engineering practice, we refer to the sum of Rw + C (or DnT,w + C), which is often recorded in nomenclature as RA1. The spectral adaptation index C (defined in ISO 717-1) is used to assess the insulation of partitions against flat-spectra noise (pink noise), such as: daily activities, conversations, children's play, fast train movements, or industrial plants emitting medium- and high-frequency noise. This distinguishes it from the Ctr index, which is mainly applied to traffic noise with a predominance of low tones.

Acoustics in Simple Words

If we treat the Rw index as the general "shield strength" protecting against noise, then the index with adaptation C tells us how that shield performs against a specific type of "weapon" – in this case, against everyday noise (conversations, television, music without strong bass). It's like testing a window's airtightness not against a hurricane (for that Ctr would be used), but against a normal, urban breeze or the chatter of conversations in the yard. This value (RA1) is usually slightly lower than Rw itself, as it is more stringent and realistic for typical household sounds.

Summary

The insulation evaluation index considering correction C (denoted as index A1) serves to accurately determine protection against residential noise. It is essential when selecting partition walls in residential buildings, where the main source of disturbances is neighbors.