1. INTRODUCTION
In the wearable computing environment, a HMD (head mounted display) is commonly used to browse the World Wide Web, read e-mail, and watch other visual information. However, it is difficult for users to see the display for a long time because the displays are very small and staring at a small display is tiring on the eyes. Furthermore, in many cases, a display is provided only for a single eye. To solve these problems, many researchers are considering audio interaction, and various studies of this have been done. Audio interaction lets users browse a lot of information while doing something such as walking or cooking.