Calculation of opinion scores for telephone connections

Abstract
The British Post Office telephone network is planned to achieve a certain standard of transmission performance, and this is expressed in terms of the percentage of telephone connections capable of providing a defined degree of customer satisfaction when used for conversation. At present, the basic fundamental data required for this assessment procedure have to be obtained by laboratory tests using subjects; such tests are expensive, time consuming and rather imprecise, unless conducted on a large scale. Efforts have continually been made, at least from 1929, to replace such testing methods by objective determinations based on physical measurements and calculations. This art has now reached the stage that a practical calculation procedure can be described that is based on a new theoretical model, and makes use of modern electroacoustical measuring methods. The paper describes the theoretical model, indicates how the various parameters have been estimated and shows how subjective- assessment scores can be reproduced by a calculation procedure, with a fairly satisfactory agreement between calculation and experiment. It has been necessary to include in the model certain special features peculiar to telephony; e.g. allowance has to be made for an increase in the subjective score when subjects become adapted to rather inferior performance. Further improvement is desirable, and this depends on the continuation of studies in certain areas, which are indicated

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