Determining the effects of new types of impairments on perceived quality of a voice service

Where a first communication service exhibits a first performance characteristic affecting communication quality and a second communication service exhibits both the first performance characteristic and a second performance characteristic not exhibited by the first communication service, a method for determination the effect of the second performance characteristic upon the quality of the second communication service comprising the steps: Establishing communications via the second communications service (702); Obtaining objective measures of the first performance characteristic as the second performance characteristic varies (704); Converting the objective measurement of the first performance characteristic into subjective rating based upon knowledge of the first communication service (706, 708, 710); Altering the subjective ratings to reflect the effects of the second performance characteristic by use of an assumed model for the effects of the second performance characteristic upon the subjective ratings of the first performance characteristic (712); Computing quality index values from the altered subjective ratings (712); and Adjusting the assume model to improve the correlation between the quality index values and the second performance characteristic (714)