Design of stepped exponential horns for acoustic energy transfer systems

Stepped exponential horns are proposed as a measure of acoustic impedance adaptation in an acoustic energy transfer (AET) system. Resonances due to impedance mismatches in the horn are used to obtain a maximal power throughput at a single frequency. Finite element (FE) models are used for optimisation of the horn parameters. Although experimental results do not match particularly well with simulations, the results still look promising. The horns boost the power transfer and efficiency for greater distances, which was one of the major problems in prior AET systems. The measured output power increased by a factor 3.1 and the efficiency by a factor 7.5 at a distance of 10cm between the transmitter and the receiver. Discrepancies between the model and the measurements are expected to be largely due to variations in transducer parameters. The transducer losses were measured separately by means of impedance measurements in vacuum for improvement of the FE model.