osses on a telephone connection. As we discussed in Chapter 2, losses are conventionally measured in decibels. Thus the unit of measure of "hearing sufficiently well" is the decibel. From the present 3.2 QUALITY OF SERVICE: VOICE, DATA, AND IMAGE method of measurement we derive the loudness rating, abbreviated LR. It had several predecessors: reference equivalent and corrected reference equivalent. 3.2.2.2 Reference Equivalent. The reference equivalent value, called the overall reference equivalent (ORE), was indicative of how loud a telephone signal is. How loud is a subjective matter. Given a particular voice level, for some listeners it would be satisfactory; for others, unsatisfactory. The ITU in Geneva brought together a group of telephone users to judge telephone loudness. A test installation was set up made up of two standard telephone subsets, namely, a talker's simulated subscriber loop and a listener's simulated loop. An adjustable attenuating network was placed between the two simulated loops. The test group, on an individual basis, judged level at the receiving telephone earpiece. At a 6-dB setting of the attenuator or less, calls were judged too loud. Better than 99% of the test population judged calls to be satisfactory with an attenuator setting of 16 dB; 80% rated a call satisfactory with an ORE 36 dB or better, and 33.6% of the test population rated calls with an ORE of 40 dB as unsatisfactory, and SO on. Using a similar test set up, standard telephone sets of different telephone adminis- trations (countries) could be rated. The mouthpiece (transmitter) and earpiece (receiver) were rated separately and given a decibel value. The decibel value was indicative if they worked better or worse than the telephones used in the ITU laboratory. The attenuator setting represented the loss in a particular network connection. To calculate overall refer- ence equivalent (ORE), we summed the three decibel values (i.e., the transmit reference equivalent of the telephone set, the intervening network losses, and t