| 摘要 |
A method and apparatus for monitoring a predetermined condition of a medium by; transmitting acoustical waves through the medium, continuously measuring changes in the transit time of the acoustical waves resulting from changes in the monitored condition; and utilizing the changes in transit time to provide a continuous measurement of the changes in the monitored condition. The acoustical waves are bending waves wherein cross-sections of the medium have a rotational movement orthogonally to the axis of propagation of the waves through the acoustical channel. Several examples of such method and apparatus are described, including a highly sensitive pressure sensor for sensing changes in pressure applied to a displaceable membrane, and a highly-sensitive vibration sensor for sensing earth or other vibrations.
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