Air pressure variation detector

An air pressure variation detector comprising:

• a base plate having a through hole or a cavity;
• a piezoelectric element equipped on both the surfaces thereof with electrodes, formed in a strip-like shape having a width narrower than the inside width of said through hole or cavity and a thickness thinner than 300 .mu.m, and fixed to said base plate in the form of a cantilever;
• an impedance converter circuit consisting of a field effect type transistor and a leak resistor;
• and
• an electrically conductive accommodating container having a vent hole;
• said base plate and said piezoelectric element being disposed within said accommodating container;
• and
• said air pressure variation detector being adapted to be capable of detecting variations of pressure of air admitted into said accommodating container through said vent hole by:
• an end of said piezoelectric element being supported on said base plate so that said piezoelectric element can be vibrated in said through hole or cavity of said base plate,
• an output terminal of said piezoelectric element being connected to a gate of said field effect type transistor of said impedance converter circuit, and
• said leak resistor being connected between said gate and a ground terminal of said piezoelectric element.