Patent ID: 6366675
Filing Date: 2002-04-02
Classification: A61B,G01H

Abstract:
A sound pressure detecting system comprising:a piezoelectric substrate having an upper- and a lower end surfaces being parallel to each other; an input interdigital transducer having an arch-shape and formed on said upper end surface of said piezoelectric substrate, the thickness of said piezoelectric substrate being smaller than an interdigital periodicity of said input interdigital transducer; an output interdigital transducer having an arch-shape and formed on said upper end surface of said piezoelectric substrate, said input- and output interdigital transducers making a pair with a concentric center; a liquid cavity having a liquid in contact with said lower end surface of said piezoelectric substrate; an air cavity; a partition wall between said liquid cavity and said air cavity, said partition wall being made of a polymer film with elasticity; a signal analyzing unit connected between said input- and output interdigital transducers: and a monitor connected with said signal analyzing unit, said piezoelectric substrate, and said input- and output interdigital transducers forming a detecting assembly, said input interdigital transducer receiving an input electric signal with a frequency approximately corresponding to said interdigital periodicity, exciting a leaky elastic wave in said piezoelectric substrate, and causing a mode conversion from said leaky elastic wave, having the wavelength approximately equivalent to said interdigital periodicity, to a longitudinal wave in said liquid, said partition wall reflecting said longitudinal wave, said output interdigital transducer detecting a reflected longitudinal wave as a delayed electric signal with a frequency approximately corresponding to said interdigital periodicity, said signal analyzing unit sensing a sound pressure through said partition wall via said air cavity in terms of a change in said delayed electric signal, and said monitor displaying said sound pressure.