9  Sound Isolation

Noise Design Criteria

Single figure values in dBA cannot be taken as being reliable for design purposes as they give no indication of the frequency spectrum. The list below may nevertheless be of some use in stating an approximate indication of loudness (dBA) and also the approximate NC and NR (see Figures 16 and 17).

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Figure 16  ISO noise rating (NR) curves

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Figure 17  Noise criteria (NC) curves

Environment

NC/NR index

Equivalent dBA

Entertainment:

Concert hall, theatre

20–25

30–35

Lecture theatre, cinema ...

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