Overcoming the Lack of Screen Space on Mobile Computers

One difficulty for interface design on mobile computers is lack of screen space caused by their small size. This paper describes a small pilot study and two formal experiments that investigate the usability of sonically-enhanced buttons of different sizes. The underlying hypothesis being that presenting information about the buttons in sound would increase their usability and allow their size to be reduced. An experimental interface was created that ran on a 3Com Palm III mobile computer and used a simple calculator-style interface to enter data. The buttons of the calculator were changed in size between 464, 868 and 16616 pixels and used a range of different types of sound from basic to complex. Results showed that sounds significantly improved usability for both standard and small button sizes - more data could be entered with sonically-enhanced buttons and subjective workload reduced. More sophisticated sounds that presented more information about the state of the buttons were shown to be more effective than the standard Palm III sounds. The results showed that if sound was added to buttons then they could be reduced in size from 16616 to 868 pixels without much loss in quantitative performance. This reduction in size, however, caused a significant increase in subjective workload. Results also showed that when a mobile device was used in a more realistic situation (whilst walking outside) usability was significantly reduced (with increased workload and less data entered) than when used in a usability laboratory. These studies show that sound can be beneficial for usability and that care must be taken to do testing in realistic environments to get a good measure of mobile device usability.