Patent ID: 6770032
Filing Date: 2004-08-03
Classification: G01H

Abstract:
A passive acoustic sensor for determining the value of a physical variable in a measurement region, the sensor comprising:a housing having two spaced apart substantially parallel and substantially flat acoustically reflecting surfaces, at least one of said acoustically reflecting surfaces is a surface on a movable member configured to be movable with respect to said housing such that the distance between said acoustically reflecting surfaces varies as a function of said physical variable, said acoustically reflecting surfaces are configured such that when incident acoustic waves having a range of frequencies are directed at said sensor in a direction substantially orthogonal to said acoustically reflecting surfaces, a first portion of said incident waves is reflected from one of said acoustically reflecting surfaces to form a first reflected wave and a second portion of said incident waves is reflected from the remaining acoustically reflecting surface to form a second reflected wave, said first reflected wave and said second reflected wave interfere to form a returning acoustic signal having at least one maximally attenuated frequency which is correlated with the value of said physical variable in the measurement region in which said sensor is disposed.