Recentry audio frequency standard of high stability has been in demand, and mechanical vibrators are used for this purpose generally. Tuning forks have been used as above means for many years, but they are rather suitable for the production of audible tones, than as frequency standards. The tuning-fork was replaced by a tuning bar which is a free-free bar at both ends and vibrates transversally to its long axis. We call this tuning bar "Onpen". It is a bar supported at the nodal points by supportors. This paper is a report of theoretical and experimental results on supporting methods of the tuning bar "Onpen". By treating the machanical equivalent circuits theoretically, the supporting conditions and mounting effects have been studied which lead to establishing a designing principle for the mountingmethod of the tuning bar.
