Measuring Quality and Designing for It

"Good sound" cannot be measured. What can be measured is delay, loss and jitter, and the score predicted from them. This volume divides the path into stages, follows the delay each one adds, and shows where conversation stops working. It then treats the procedure of subjective evaluation, the objective measures used in its place, and the E-model's R factor, which joins the two. It closes by setting out how voice, fax and short messages make entirely different demands of the same network: the same 5 per cent loss is an audible degradation for one and a page that never prints for another.