The most popular method of measuring intelligibility is Alcons (Articulation Loss of Consonants). It expresses intelligibility as the percentage loss of consonants.

Both EASE and EASE JR offer a choice of Alcons calculation formulas and frequencies.

2000 Hz is normally viewed as the highest frequency used to evaluate voice intelligibility. It contributes approximately 34% to overall intelligibility and for years has been used in the United States as the de facto standard for expressing intelligibility.

1000 Hz contributes approximately 25% to intelligibility and is considered by most as the middle frequency used in Alcons calculations. Many users consider 1000 Hz calculations as more stringent than 2000 Hz simulations. The reason is that the pattern control of most loudspeakers is tighter at 2000 Hz than it is at 1000 Hz and the direct to reverberant ratio is higher at 2000 Hz than it is at 1000 HZ.

500 Hz contributes only about 16% to intelligibility and is often overlooked in intelligibility studies.

EASE and EASE JR provide for studies at all three frequencies.

Both 1000 Hz and 2000 Hz Alcons maps are shown above. Notice that even though there is considerable variation between the two, both clearly indicate that poor intelligibility is going to be a problem. Losses of 10% or more generally indicate poor intelligibility.

EASE and EASE JR also provide a choice of three calculation formulas, either the Short Form or the Long Form formulas developed by Peutz or the TEF20 formula.