Abstract
We show that the quality factor of a small passive acoustic radiator is fundamentally limited by its volume normalized to the emitted wavelength, imposing important constraints on the bandwidth and efficiency of compact acoustic sources. We overcome this bound, known in electromagnetics as Chu’s limit, by realizing a piezoelectric transducer loaded with a non-Foster circuit, showing that its radiation bandwidth is fundamentally limited only by stability considerations. Based on these principles, we experimentally observe over a threefold bandwidth enhancement compared to its passive counterpart, paving the way towards non-Foster acoustic elements and metamaterials that overcome the bandwidth constraints of passive systems.
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