Liquid volume measurement with a closed Helmholtz resonator under micro-gravity conditions

We attempted to apply the Helmholtz resonance technique to cryogens to confirm the applicability of the technique for measuring liquid volume under micro-gravity conditions. An experimental cell, which is regarded as a closed Helmholtz resonator, was prepared and liquid nitrogen used as a test liquid. A swept frequency signal was added to a loudspeaker and the acoustic response was detected by measuring the electrical impedance of the loudspeaker’s voice coil. The Helmholtz resonance frequency was analyzed by use of the maximum entropy method. The Helmholtz resonance frequencies obtained under micro-gravity conditions agreed with the resonance frequencies obtained under terrestrial conditions. We confirmed that the Helmholtz resonance technique is applicable to cryogens under micro-gravity conditions.