A panel structure including a flexible panel, at least one edge strip and mounting hardware is provided. The imaginary sound source is imagined to produce the audio sounds at a location spaced apart from each of the loudspeakers. The first dielectric layer includes overhangs in the spaces between two neighboring metal layers and voids under the overhangs. The higher-k material may be present at a lower concentration. When charging the capacitive electronic part has progressed sufficiently, the switch is controlled to open.