McGookin, David Kerr
Understanding and improving the identification of concurrently presented earcons.
PhD thesis, University of Glasgow.
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The use of sound to communicate information as part of a user interface has been an active research area for several years. Research has shown that sound can be concurrently presented to users to increase the bandwidth and rate of data presentation. However, when sounds are concurrently presented, they may interfere with each other, such that determining the data encoded in the sound becomes difﬁcult. Modiﬁcations to the sounds can help to avoid such interference, but due to the nature of the sounds the impact of the modiﬁcations may be constrained.
This thesis investigates such interaction with concurrently presented earcons. One experiment investigates how the identiﬁcation of earcons is affected by the number concurrently presented. It was found that increasing the number of earcons concurrently presented lead to a signiﬁcant decrease in the proportion of earcons and their attributes successfully identiﬁed by participants. With identiﬁcation falling from 70% correct for one presented earcon to 30% for four concurrently presented earcons.
A second experiment identiﬁed how modiﬁcations to the design and presentation of concurrently presented earcons affected their identiﬁcation. It was found that presenting each earcon with a unique timbre as well as introducing an onsettoonset delay of at least 300ms caused a signiﬁcant improvement in earcon identiﬁcation, and the timbre encoded attribute of earcons. However overall identiﬁcation levels remained low at around 30%.
Two further experiments investigated the impact of spatialisation on concurrent earcon identiﬁcation. They showed that spatial presentation of earcons which did not incorporate the ﬁndings of the previous experiment signiﬁcantly improved identiﬁcation of earcons and the register encoded earcon attribute, over earcons that were not spatially presented but did incorporate the ﬁndings of the previous experiment. Another experiment showed that spatial presentation of earcons which incorporated the unique timbre and 300ms onsettoonset modiﬁcations signiﬁcantly improved the identiﬁcation of the timbre encoded earcon attribute, although overall identiﬁcation remained low.
These four experiments yielded a set of guidelines for concurrent earcon presentation. Due to the nature of those experiments however, a further experiment was conducted to determine the impact of the guidelines on more ecologically valid tasks. A set of modiﬁed and unmodiﬁed earcons which represented entries in a mobile diary system were compared. Overall task accuracy remained low, although participants rated the modiﬁed earcons to require signiﬁcantly less subjective workload.
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