This Recommendation contains the essential particulars for defining the method for determining loudness ratings in accordance with Recommendation P.76 when use is made of subjects performing equal loudness balances. Details are included concerning the balancing method, choice of subjects, speech material, design of experiment, method of analysis and presentation of results.
The method described in this Recommendation requires both the “unknown” telephone system whose loudness rating is to be determined and the IRS to be balanced against the Fundamental Reference System NOSFER. An alternative method, in which the “unknown” is directly balanced against the IRS, is described in Annex D.