Determination of the minimum length impulse response for time reversal focalization in acoustic cavities.

摘要

In time reversal focalization of acoustic waves, the identification of the system dynamics is usually made in the time domain by sending a short temporal pulse and acquiring the impulse response signal at the focus point. In the case of metallic acoustic cavities, the focalization can be obtained using only one transducer, by putting in phase all the frequency components of the impulse response. In several practical applications, the set of possible focus points must be pre-calibrated, forming a "library" of impulse responses. At the start of these experiments two parameters must be determinate, the sampling frequency and the temporal duration of the acquiring window. In this work, the dependence of the focus amplitude with the sampling frequency and the temporal window is investigated. The practical goal is to obtain the impulse response that allows the time reversal focalization using the minimum memory size and without appreciable loss of amplitude. The results show that there exist a maximum useful sampling frequency and a maximum useful temporal window from which there are not significant increases in the focus amplitude. In that sense, a minimal impulse response is obtained.