Acoustic insertion loss measurement using time reversal focusing

Abstract

Accurate measurement of acoustic insertion loss has important applications in evaluating the performance of acoustic filtering material. In a typical procedure for insertion loss measurement, two pulses are recorded: one without and one with the specimen inserted between the transmitters and receivers. The amplitude spectra of the two pulses are then used to determine the insertion loss, which is a function of frequency. The measurement with low frequencies is quite difficult because of the reverberation interference, which is induced by the sides of vessel where the absorption materials cannot work well and fail to produce an acoustic free field environment. This presentation presents a method which uses time reversal (TR) focusing technique to measure the insertion loss of acoustic filtering materials. The experiment results in a waveguide water tank show that the approach can achieve high signal-to-reverberation ratio in the measurement. Besides, TR focusing provides high resolution at the place of the specimen which reduces the requirement of the specimen size. [Work supported by the National Natural Science Foundation of China under grant no 61171147.]