Designing earcons with musical grammars

Many blind and partially-sighted computer users have come to rely on auditory computer interfaces to interact with their computer. By recognising sounds made by the computer, blind users can extract information from the auditory display which is presented visually to sighted users. Sighted users can also benefit from using an auditory interface in conjunction with their existing visual display.Earcons have evolved as a means of representing concepts in such auditory displays as short sound motives. These motives usually consist of a small number of notes, with a distinct rhythm and dynamic contour. They are constructed according to rules devised by Blattner [1] and developed by Brewster et al. [2, 3]. Although they appear to be musical fragments, many fundamental musical concepts are not taken into account during their design.In fact, many early earcon designers tended restrict the maximum number of notes within an earcon to four, as any longer sequence would have a melodic connotation. The presence of a tune was thought to be distracting and hence the use of musical tensions, etc. was avoided. Instead of shying away from the powerful capabilities music affords, it is postulated here that musical structures should be used to our advantage, to remove the tight restrictions placed upon the design of earcons.It is proposed that the use of a musical grammar during the design of a set of earcons can impose a number of valuable constraints upon the choice of earcon motif. These constraints are advantageous as they allow a basic structure to be built into the surface form of each earcon. This in turn allows only certain combinations of earcons to combine with each other. A grammatical property is therefore imposed upon the interface which provides extra feedback to the user when inappropriate combinations occur.