| 摘要 |
A method of and an apparatus for determining sound propagation speed in a medium which is subject to variations in this speed. A measuring tube containing the medium is energized by a loudspeaker (ultraacoustic transducers) with a controllable energizing frequency in resonance with the measuring tube containing a column of the medium to be evaluated. The resonant output frequency is detected and modulated with a low frequency signal and the mean value of the modulated output signal is formed and counted. For a predetermined count, the elapsed time is measured and from this value the propagation velocity is calculated.
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