resonator

n. [ NL. & G. ] 1. (Acoustics) Anything which resounds; specifically, a vessel in the form of a cylinder open at one end, or a hollow ball of brass with two apertures, so contrived as to greatly intensify a musical tone by its resonance. It is used for the study and analysis of complex sounds. [ 1913 Webster ]

2. Anything that resounds or resonates; specif.: (a) (Teleg.) An open box for containing a sounder and designed to concentrate and amplify the sound. (b) (Elec.) Any of various apparatus for exhibiting or utilizing the effects of resonance in connection with open circuits, as a device having an oscillating circuit which includes a helix of bare copper wire, a variable number of coils of which can be connected in circuit with a condenser and spark gap excited with an induction coil. It is used to create high-frequency electric brush discharges. (c) (Wireless Teleg.) The antenna system and other high-frequency circuits of a receiving apparatus. [ Webster 1913 Suppl. ]