Early energy ratios
The early to late index, or clarity, is
(4)
where te is the early time, typically 80ms for music application and 50ms for speech or stage evaluation.
The early to total index, or definition, is
(5)
Definition is mostly used for speech signals, and the early time is usually taken as 50ms.
The upper integration limits are taken as the truncation point determined in the decay curve formation, or the end of the impulse response, according to the integration option specified. If compensation for truncated energy is calculated, this is taken into account as well to increase accuracy.
The early limits can be changed to numbers other than recommended in the standard. For Clarity, it is also possible to get two values as output of the calculation if two numbers are typed, separated by a ‘&’. For example, ‘50&80’, which is the default setting, gives the two clarity values C50 and C80 as output. Note that this applies when writing parameters to grid or text file, when using the Room Ac. Parameters plot type, only one parameter is plotted, and the lowest early time is used, in this example C50.