Electromechanical transducer and method for detecting a sensitivity change of the electromechanical transducer

An electromechanical transducer comprising: a plurality of elements, each element comprising a first electrode and a second electrode, with a gap between the first electrode and the second electrode; voltage applying unit configured to apply to the first electrode AC voltage; and a sensitivity change calculation unit is configured to use due to the application of the AC voltage signal to calculate a second output electrode of each of the element from the element for sensitivity variations.