| 摘要 |
A sound pressure sensing device comprises a piezoelectric substrate, an input interdigital transducer, a first output interdigital transducer, a second output interdigital transducer, a diaphragm, a liquid tank, and a signal analyzer. All the input-, the first output-, and the second output interdigital transducers are formed on one end surface of the piezoelectric substrate. The liquid tank has a liquid in contact with the other end surface of the piezoelectric substrate and an inner surface of the diaphragm. If an input electric signal is applied to the input interdigital transducer, an elastic wave is excited in the piezoelectric substrate. A leaky component of the elastic wave is radiated effectively in the form of a longitudinal wave into the liquid. The longitudinal wave is reflected in the liquid by the diaphragm. A reflected longitudinal wave is detected at the first output interdigital transducer as a first delayed electric signal. A non-leaky component of the elastic wave is detected at the second output interdigital transducer as a second delayed electric signal. A sound pressure caused by touching an outer surface of the diaphragm is sensed by the signal analyzer from a difference between the first- and second delayed electric signals.
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