Models for the Subjective Effects of Loss, Noise, and Talker Echo on Telephone Connections
James R. Cavanaugh, R. W. Hatch, J. L. Sullivan · Bell System Technical Journal · 1976
Tests have been conducted at Bell Laboratories within the last 10 years to obtain subjective evaluations of the effects of loss, noise, and talker echo on telephone transmission quality. We use these subjective test results to formulate graphical and analytical models of subjective opinion that can be used in network planning studies to evaluate transmission performance of the network and to study the effects of network changes on performance. These models are based on the concept of a generalized transmission-rating scale. Separate opinion curves for each test take into account differences caused by factors such as subject group, type of test, and range of conditions. We also describe the methods of data analysis used in the formulation of the transmission-rating scale and opinion models, provide a comparison of the test results with the models, and discuss the models in sufficient detail to permit their application in transmission planning studies.