A planar acoustic transducer for near field acoustic communication using evanescent wave

摘要

A planar acoustic transducer for near field acoustic communication using evanescent wave is proposed. We focused on that the evanescent wave decays away with distance from sound source. This phenomenon can be useful for preventing privacy divulgation and noise production during communication since acoustic signal in evanescent wave field can only reach to the vicinity of the source. We attempt to generate the evanescent wave in audio frequency with large level enough to receive by mobile devices equipped with microphones. The acoustic transducer which consists of a single vibration plate is designed with help of finite element analysis (FEA). Moreover, the acoustic transducer is made with design-based shape, and we measured the distribution of sound pressure level of the sound field above the acoustic transducer in experiment. The obtained results suggest that the proposed acoustic transducer can generate the evanescent wave because amplitude of sound pressure was attenuated exponentially. In addition, evanescent sound field was generated quasi uniformly by attaching the damper at the end of the plate. This result suggests that mobile devices can receive acoustic data at any point near the plate. Receivable distance from the surface of the proposed acoustic transducer was shorter than that of a planar acoustic transducer driven uniformly. Therefore, the acoustic transducer is expected to be utilized for near field acoustic communication without divulgation privacy and acoustical noise production.