A development of the Collard principle of articulation calculation

Many rather laborious talker-listener assessments of speech links could be avoided if the theoretical framework propounded in 1929 by Collard were more generally applied. This theory permits the articulation score to be calculated, given the frequency characteristics, noise level and transmission losses of any telephone circuit. The paper expresses this principle in terms of a simple mathematical model defined by a very few parameters which have been estimated from recent measurements made by the Post Office. The practical application of these results to the calculation of articulation can be reduced to a convenient procedure which is described in an appendix and illustrated with some numerical examples. Measurements and calculations based on the theory agree under favourable conditions to within a few per cent of sound articulation; when commercial subscribers´ sets are involved, however, a careful choice must be made of the method of measuring the sensitivity/frequency characteristics of the transducers. Although actual articulation measurements cannot yet be completely dispensed with, the calculation technique does enable a large amount of information to be interpolated from a relatively small number of measurements on key conditions.