Web-based discussion forums enable users to share knowledge in straightforward and popular platforms. However, discussion forums have several problems, such as the lack of immediate delivery and response, the heavily text-based medium, inability to hear expressions of voice and the heuristically created discussion topics which can impede the educational process. The need to share knowledge is not restricted to web text-based environment, since knowledge lives in the world, and mobile applications supply students with the opportunity of ubiquitous learning. This study introduces mobile phones and voice discussion into a web discussion forum, and presents a ubiquitous ontology-based knowledge forum that allows students to extend learning experiences anytime and anywhere to facilitate the exchange of voice and text knowledge. The learning system environment and design approach to tackling adaptive text/audio display on small mobile phones is illustrated. Preliminary evaluation of the experiment indicates that around 74% of students are pleased with the system and benefit significantly from sharing voice knowledge. The proposed system can offer flexibility in discussion for a distance learning environment.