Measurement of Neutral Gas Using Dispersion Characteristics of Sound Waves

概要

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The phase velocity $v$ of a sound wave with angular frequency $\omega$ increases as gas pressure $ p$ decreases, and $v/c_{\text{s}}$ is represented by $r= p/\mu\omega$ in the range of $0.1<r<10$, where $\mu$ is the gas viscosity and $c_{\text{s}}$ is the sound velocity, given by $(\gamma k_{\text{B}}T/m)^{1/2}$ ($\gamma$: ratio of specific heat, $k_{\text{B}}$: Boltzmann constant, $T$: temperature, $m$: mass of gas molecule). This indicates that gas pressure can be evaluated by the measurement of the phase velocity of a sound wave with one frequency if gas temperature is known, or gas temperature can be evaluated by the measurement of the phase velocity of a sound wave with one frequency if gas pressure is known. In this paper, we present a new method for evaluating gas pressure and temperature simultaneously by the measurement of the phase velocities of sound waves with two different frequencies using propagation characteristics.
2006-10-30