[9.4.5] A number indicating cavity proportions.

The cavity ratio is computed from:

CR = \frac{5 \left ( Height_{cavity} \right ) \left ( Length_{cavity} + Width_{cavity} \right )}{\left ( Length_{cavity} \right ) \left ( Width_{cavity} \right )}

For cavities of irregular shape:

CR = \frac{2.5 \left( Height_{cavity} \right ) \left ( Perimeter_{cavity} \right )}{(Area of Cavity Base)}

 Note: The relationship between cavity ratio and room coefficient (K_r) should be noted. If the entire room is considered as a cavity, the room height becomes Height_cavity, and CR = 10 K_r.