Juha Marila

Design of Dynamic Vibrotactile Textures

This paper describes a method for creating virtual textures without force feedback by using a simple motion sensor and a single vibrotactile actuator. It is based on wavetable synthesis driven by the users hand movements. The output of the synthesis is rendered with the tactile actuator attached in a hand-held box together with the motion sensor. The method provides a solution for creating tangible properties for virtual objects which can be explored by pointing at them with the sensor-actuator device. The study introduces 12 virtual textures which were based on three different envelope ridge lengths, two spatial densities, and were either regularly or irregularly organized. To evaluate the role of each design parameter in the perception of the texture, a series of experiments was conducted. The perceived similarity was assessed in a pairwise comparison test and the outcome was analyzed by using multidimensional scaling. The analysis revealed that envelope ridge length and spatial density were distinguishable design parameters while regularity was not. The textures were also rated according to five attribute scales previously determined in the pilot experiment. The results show that ridge length and spatial density influence perceived roughness and flatness similarly as with real textures.

Time-out in user interface: the case of mobile text input

In many user interfaces with restricted input capabilities, a time-out is used to automatically change the user interface (UI) from one mode to another. In this paper, we study the learning of time-outs and the effect of feedback on it in the case of mobile phone text entry. The effects of three different feedback schemes (auditory/visual/no feedback) on the learning of two different time-out lengths were compared. We measured the response time (RT) from the time-out occurrence to the time of the user’s action. Error rates and the development of the RTs in different schemes were used as measures of learning. We also studied if the users learned to estimate the time-out lengths, or if they just reacted to the available feedback. There were three main findings. Without feedback, RTs had a great variation. Auditory feedback enabled faster RTs than visual feedback. Finally, we found evidence of short-term learning, but not much of a lasting effect. The possible application of adapting time-out length to user RT is discussed.

Structured Menu Presentation Using Spatial Sound Separation

This paper describes a technique to support user interaction in a hierarchical menu, based on spatial sound separation. A complex menu structure is represented in space using a limited number of sound positions obtained by stereo panning or 3-D audio processing techniques. Spatial organisation of menu items can be designed in a logical way to provide navigation cues to the user, independent of the menu item nature. Two different strategies for menu presentation and interaction are described and compared in this paper. Finally, an application of this technique to the navigation in a large music collection is considered. This case study is an interesting example of usage situation for which eyes-free interaction would be useful, for instance on a portable audio player using headphones and a small remote control.

Time-Out in Mobile Text Input: The Effects of Learning and Feedback

In many user interfaces with restricted input/output capabilities, a time-out is used to automatically change the UI from one mode into another. In this paper we studied the learning of time-outs and the effect of feedback on it in mobile phone text entry. The effects of three different feedback schemes (auditory/visual/no feedback) on learning of two different time-out lengths were compared. We measured the response time from the time-out occurrence to the time of user’s reaction. Error rates and the development of the response times in different schemes were used as measures of learning. We also studied if the users learned to estimate the time-out lengths, or if they just reacted to the available feedback. There were three main findings. Without feedback, response times had great variation. Auditory feedback enabled faster response times than visual. Finally, we found evidence of short-term learning, but not as much of a lasting effect.