Effect of Presenting Multiple vs. Single Rating Scales After Stimulus Presentation on Subjective Quality Ratings

Abstract

This contribution is a continuation of the already present results of ITU-T Contribution 12-113 [1]. As widely known subjective test methods if used as originally intended are valid tools for the assessment of e.g. the speech quality using the absolute category rating [ACR] method [2]. For a more complex scenario such as for example the assessment of noise suppression algorithms multiple scales have to be rated by subjects. In case of the ITU-T Recommendation P.835 [3] ratings for speech signal alone, the background noise alone, and overall quality are asked. In ITU-T Contribution 12-113 [1] the effect of the order of items presented in blocks of three after the stimulus presentation was discussed. It could be shown that the order of scales had a significant impact on the rating of the speech signal and background noise. This contribution presents the results of quality ratings – performed ITU-T Recommendation P.835 [3] conform – which were obtained by rating on a single scale, one scale after each stimulus, and in blocks of three items after each stimulus presentation.