Clarity, definition and centre time#
For the definitions below, time zero is the response arrival origin, rather than source emission. The applicable build's direct-arrival/onset convention determines that origin. These formulas describe the retained energy response; limited late energy can bias early/late ratios and centre time.
Clarity (C50 and C80)#
Clarity C50 and C80
Clarity compares early and late received energy, using a 50 ms boundary for C50 or 80 ms for C80 measured from the response arrival origin.
- e(t)
- Receiver energy per unit time in one octave band (consistent energy unit/s)
- t, τ
- Time measured from the response arrival origin (s)
- tₑₙd
- End of the retained response (s)
- CΔ
- Clarity for the selected boundary (dB)
- Δ
- Early/late boundary (s)
Definition (D50)#
Definition D50
D50 is the percentage of retained energy arriving within the first 50 ms, measured from the response arrival origin.
- e(t)
- Receiver energy per unit time in one octave band (consistent energy unit/s)
- t, τ
- Time measured from the response arrival origin (s)
- tₑₙd
- End of the retained response (s)
- D₅₀
- Early-energy definition (%)
Centre time (Ts)#
Centre time
Centre time summarises when energy arrives within the retained response. It is expressed in seconds; multiply by 1,000 for milliseconds.
- e(t)
- Receiver energy per unit time in one octave band (consistent energy unit/s)
- t, τ
- Time measured from the response arrival origin (s)
- tₑₙd
- End of the retained response (s)
- tₛ
- Centre time (s)
Zero or unsupported energy denominators do not establish a finite metric. Retain the output's availability and limitation rather than interpreting a missing value as zero.
Clarity by frequency and position#
Octave-band C50 and C80 describe how clarity varies with frequency and listening position.
Direct-to-reverberant ratio (DRR)#
Direct-to-reverberant ratio (DRR) expresses the balance between direct and reflected sound energy at a listening position, in decibels.
Direct-sound status#
Direct-sound status indicates whether direct sound is recorded at a listening position or the result is unavailable. No direct sound recorded does not, by itself, establish a physical obstruction.