A sensing device and method. The device includes a first element and a second element. Each of the elements includes a first electrode, and a second electrode, and a piezoelectric layer between and connected to the first and second electrode. The first electrode, second electrode and piezoelectric layer of each element form a pressure wave transducer. The first and second elements are oriented such that the second electrode of the first element faces the second electrode of the second element. The elements are displaced from one another such that the second electrodes form the plates of a capacitor.