ABSTRACT
The outdoor acoustical environment varies dynamically in magnitude and character throughout most communities. The sound level variation can be temporal, spectral, or spatial. Perhaps the foremost function of describing community noise is to relate the physical properties of the sound environment to human reaction or response. The articulation index (AI) is a single-number parameter used for predicting speech intelligibility. The index is determined by comparing the level of intruding speech to the level of the background noise at a given listening location. The measurement and calculation procedure used to determine the index is both involved and time consuming, and the index is rarely applicable to industrial noise control. With the number of descriptors, rating schemes, etc., the questions of which to use and when cannot be answered simply. The complexity of the human response along with the number of acoustical variables continues to confound the scientific community.
