523 C.M.R. 12.10
There must be a bell, gong, or airhorn at the ring or, if the contest or exhibition is held in a fenced area, at the fenced area. The bell, gong, or airhorn must produce a clear tone easily heard by the unarmed combatants.
REGULATORY AUTHORITY
523 CMR 12.00: M.G.L. c. 147, § 46.