Communicability testing for voice communications

Traditionally, the performance of low bit rate coders was measured by two performance characteristics, namely quality and intelligibility. However, those characteristics are not adequate for measuring the performance over a realistic communication link, where factors such as channel conditions (errors, delay, etc.), dynamic speaker compensation (raising the voice under noisy acoustic conditions), and speakers´ capability of interruption, also play a role. Communicability tests were designed for this purpose. This paper is meant to be an introduction to four communicability tests proposed for the selection of the STANAG 4591 coder. The four tests have many features in common. They differ mainly in the type of task used to exercise the communication system. Two of these tasks are variations of games battleship and blackjack, the remaining two tasks are proof reading and determining differences between photographs.