시역전 기법을 이용한 음향신호의 재현

Abstract

The concept of Time Reversal Acoustics(TRA) provides an elegant possibility of both temporal and spatial concentrating of acoustic energy in highly inhomogeneous media. We explored a possibility of generating acoustical signals with arbitrary waveforms using the TRA Focusing System(TRA FS). A method of prediction of the TRA focused ultrasound waveforms using the measurements of transfer function relating the signal at the TRA transmitter to that at the focusing point has been developed. The developed approach forTRA focused signal waveform prediction from the results of direct signal easurements was tested on 10 channel TRA FS based on aluminum resonator with glued piezotransducers. The TRA FS operated in the frequency band of 100‐1000 kHz. The formation of ultrasonic signals with various envelopes was demonstrated experimentally. The calculated and experimentally measured waveforms were practically identical. We formed triangular, rectangular, and amplitude modulated tone burst signals with different modulation frequencies in the focal region. The level of side lobes in the generated signalswas much lower than that for standard TRA focusing.