The CMU uses the values in the correction tables to interpolate correction factors at arbitrary frequency and level values. The following rules apply:
At constant frequency, the correction value associated with the level point Pm is valid in the level range between (Pm+1 + Pm)/2 and (Pm–1 + Pm)/2: The ranges with constant value adjoin each other in the middle between two consecutive level points.
At constant level, the correction factors are linearly interpolated between consecutive frequency points.