Strutt|Auditorium Acoustics|Speech Clarity (D50) calculates the objective speech clarity index `D_(50)` (definition, or Deutlichkeit) based on the early (0-50 ms) and late (>50 ms) components of the sound field, either measured or calculated using the Early Sound Level (Speech) and Late Sound Level (Speech) calculations.
Strutt implements the calculation as:
`D_50 = (int_0^50 p^2(t)dt)/(int_0^oo p^2(t)dt) = 10^(G_(0-50)/10)/10^(G_(0-oo)/10)` i.e. `D_50` is essentially the proportion of early energy in the sound field
Note that `D_50` is related and convertible into to the vocal clarity index `C_50` as follows:
`C_50 = 10log(D_50/(1-C_50))`