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

Abstract

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.

The Experimental Registration of the Evanescent Acoustic Wave in YX LiNbO3 Plate

“…The existence of evanescent Lamb waves has been experimentally proven at free-edge boundaries [ 31 , 32 ], in phononic crystals [ 7 , 19 ], elastic metamaterial [ 18 ] and the possibility of their using for non-destructive control has been confirmed in [ 33 , 34 , 35 , 36 ]. These waves also could be used for development of a planar acoustic transducer for near field acoustic communication [ 37 ], passive pressure sensors for harsh-environment applications [ 38 ], new air-coupled ultrasonic for non-destructive techniques [ 39 ] and in acoustofluidic chips for microscale manipulation [ 40 ]. Despite these studies, there is still a need to develop methods for the excitation and registration of these waves.…”

An efficient subcarrier arrangement for airborne OFDM communication using parametric loudspeaker

“…Numerous studies on acoustic communication have been reported. [13][14][15][16][17][18] Compared to similar studies of wireless communication using ultrasonic waves, 19,20) there are two main advantages of wireless communication using audible sound: (1) the availability of microphones in commercial devices and (2) the ease of implementing the modem as software. On the other hand, there also two disadvantages: (1)′ the communication signal at an audible frequency is unpleasant to the human ear and (2)′ communication is not very secure.…”

Design and performance evaluation of acoustic vehicle-to-pedestrian communication system

“…[10][11][12][13][14][15][16][17][18][19][20] On the other hand, acoustic communication in the air has been limited to use in a static environment such as inter-terminal communication or information broadcasting. [21][22][23][24][25][26] This is because a large Doppler shift occurs in the received signal in a dynamic environment. The large Doppler shift in acoustic communication is a factor affecting the communication quality, but it becomes useful in measuring the relative speed between the transmitter and receiver with high accuracy.…”