Radiation from wedges of a power law profile

The large impedance contrast between bulk piezoelectric disks and air does not allow for efficient coupling of sound radiation from the piezoelectric into air. Here, we present the idea of using wedges of power law profiles to more efficiently radiate sound into air. Wedges of power law profiles have been used to provide absorption of vibrational energy in plates, but their efficient radiation of sound into air has not been demonstrated. We present numerical modeling and experimental results to demonstrate the concept. The wedge shape provides a gradual impedance contrast as the wave travels down the tapering of the wedge, while the wave speed also continually slows down. For an ideal wedge that tapers down to zero thickness, the waves become trapped at the tip and the vibrational energy can only radiate into the surrounding air. [This work was supported by institutional support [Laboratory Directed Research and Development (LDRD)] at Los Alamos National Laboratory.]