Extracting relaxational features from measurements of sound speeds for gas sensing

Abstract

In recent years, gas sensing methods by jointly measuring acoustic relaxation absorption and sound speeds have become a research focus in acoustic fields. However, the existing methods are difficult to be employed in practical gas detection due to complex measurement processes and large measurement errors when measuring the sound relaxational absorption. Furthermore, the acoustic relaxation absorption spectrum's small signal is hard to be measured because of the noise and large classical relaxation in the high-frequency range. In this paper, a gas sensing method is proposed by only measuring the sound speeds at the three frequencies, avoiding the problems of measuring the acoustic absorption spectrum. First, sound speeds are measured at three frequency points; second, the relaxation strength and the relaxation time of the acoustic relaxation features are extracted; finally, the absorption spectral peak is acquired and located for gas detection. The simulation results verify the feasibility of our method, and the detection errors from the measurement errors of sound speeds can be eliminated effectively. Thus, our work provides a high-accurate and simple acoustic method for gas sensing.