Evaluation of pertinent methods of direct and indirect scaling

In sound-quality research, a host of methodologies are employed. Often, ratings or rankings are used to assess sound-quality attributes. Sometimes, the magnitude of the sound attribute in question is directly estimated via magnitude-estimation, or production techniques. Finally, in recent years, indirect methods like multidimensional scaling, or the mathematical modeling of the listeners' cognitive decision strategies in so-called 'choice models' have been introduced to the research field. All these methodologies vary in their time-demands, they require different judgments from the listeners, and yield results of differing scale-type. In order to be able to compare some of these methods, 74 listeners were asked to make paired comparisons, magnitude estimates, similarity ratings, and to generate rank orderings of a set of environmental sounds. In result, while most methods agree on an ordinal level, the more sophisticated choice-models are both more informative with respect to the dimensional structure involved, and less compressive in the scale values obtained, when compared with the direct methods. In a parallel study, the method of magnitude-production was evaluated in greater detail, by putting the fundamental mathematical assumptions underlying the approach to an empirical test in the field of loudness fractionation. It turned out that while all subjects were able to give judgments that were valid on a ratio-scale, the numbers they used could not be taken at face value. In a second experiment, it was not possible to establish a very general class of transformation functions, that would have been able to relate the number words to their 'true,' mathematical representation. (Center contract, with participation of Christian Schmid and Oliver Baumann)