Sound emitter - Electrodynamic
Electrodynamic (sound) emitter
A (sound) emitter which depends for its operation on the motion of a conductor, joined to a diaphragm and carrying a varying current, n a steady magnetic field.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM