articulation loss of consonants (audibility) (ALcons)
ALcons, like the Speech TransmissionIndex(STI), is an evaluation method for speech intelligibility in sounded rooms and halls. As can be seen from the name Alcons, it is the loss of articulation for consonants.
Consonants play a crucial role in speech intelligibility. Therefore, the Alcons rating is based on the percentage of consonants that are not acoustically correctly understood. These are affected by reverberation, reflections, and interference in rooms exposed to sound, impairing speech intelligibility.
The ALcons value is given in percent and depends on the factors mentioned as well as on the directional characteristic of the loudspeaker boxes, the beam focusing, the distance of the listeners, the structure of the sound reinforcement room, its wall and floor characteristics, the reflections and much more.
The factors mentioned are set in relation to each other at Alcons and from this the percentage Alcons values are determined. These can range from 100% to 0%, with the 100% value representing the worst speech intelligibility and the 0% value the best.