Improvement in Transmission Characteristics in Acoustic OFDM with Adaptive Microphone Array

In this paper, we propose a microphone array method for an acoustic OFDM (Orthogonal Frequency Division Multiplexing) system. Recently, acoustic OFDM, which uses audible sound waves as an information transmission medium, has been studied. In acoustic OFDM, the transmission characteristic deteriorates owing to acoustic ambient noise because the acoustic noise corrupts audio signals containing embedded information. We therefore propose the application of a microphone array in acoustic OFDM systems. The proposed method can eliminate acoustic ambient noise by controlling the directivity of the microphone array, thus improving the transmission characteristics. We demonstrate the efficiency of the proposed method through some experimental results. Because latest mobile phones have built-in multi-microphones for noise cancellation, the proposed method can be implemented in actual mobile phones.