resonator

noun

• an apparatus that increases the resonance of a sound, especially a hollow part of a musical instrument.
• a musical or scientific instrument responding to a single sound or note, used for detecting it when it occurs in combination with other sounds.
• Physics a device that displays electrical resonance, especially one used for the detection of radio waves.
• Physics a hollow enclosure with conducting walls capable of containing electromagnetic fields having particular frequencies of oscillation and exchanging electrical energy with them, used to detect or amplify microwaves.