AudioObject 6: Examples of sonifications for three cells sampled from the ALS group, again presented in succession as in the preceding Audio Objects 4 and 5.
4.2. Performance of the sonifications and their practical use
The proteomic data sonifications demonstrated in Audio Objects 4, 5, and 6 afforded clear distinctions between the three cell types compared. The within-type comparisons showed adequate similarity for a conceptual prototype to be formed in the minds of listeners for each cell type. Indeed, after a group of naïve listeners examined these sets of sonifications, they were even able to describe the differences in such a way that they could classify new sonifications into one of the three types. Of course, the ability of naïve listeners to distinguish between classes of sonifications after some training does not imply that the sonifications will necessarily prove to be useful to practitioners. Barrass and Kramer (1999) have provided a comprehensive survey of approaches for designing sonifications that emphasizes this as an ongoing concern within existing sonification practices. Of particular relevance is their discussion regarding how knowledge derived from the perceptual evaluation of sonification can allow designers to predict how listeners will perceive (if not understand and interpret) variations in novel sonifications. The point is well made by Barrass and Kramer that the comprehensive evaluation of newly designed sonifications requires more than perceptual studies, since such studies typically do not address issues of representation that are central in sonification. Users of sonification systems need to hear the underlying data relation(s) conveyed by the sounds rather than just the changes in auditory attributes that are modulated by them.
So, beyond the elementary perceptual evaluations already undertaken, it is worth asking what other evaluation methods should be used in the further design and development of sonifications such as those presented in this paper. Further tests that address more important issues in sonification system usability must be undertaken. Ultimately, the completed sonification system must meet explicit acceptance criteria before its success is demonstrated. As outlined by Schneiderman and Plaisant (2010), these criteria for evaluating system performance might include the following:
· Time for users to learn specific functions
· Speed of task performance
· Rate of errors by users
· User retention of commands over time
· Subjective user satisfaction
In additional to the overall satisfaction with the displayed sonification that may be expressed by system users with domain knowledge whose satisfaction may diminish with time, a more objective evaluation is recommended. It is not enough that users think that they can use a system effectively; rather, it is important to determine whether users can reliably make accurate judgments regarding the information being displayed as part of a typical use-case analysis. If not, otherwise satisfying sonifications, such as those that are aesthetically pleasing, will eventually be rejected if they ultimately obtain no support or validation from the results of user testing as concerns diagnostic accuracy. Ultimately, it is hoped that such an approach will contribute to the formulation of a more generally acceptable theory of sonification. Incorporating the results of empirical tests might allow sonification theory to evolve through a somewhat natural “winnowing out” of unsuccessful approaches, supporting a general approach to sonification that can potentially provide truly winning applications that fill gaps between existing information displays.