Abstract: A piezoelectric vibrator comprising: a thin rectangular piezoelectric plate formed of a material having a Young's modulus having to short edges surfaces and two long edge surfaces and two long planar face surfaces which plate has transverse resonant vibration modes parallel to its short edges and longitudinal resonant vibration parallel to its long edges and is formed with at least one cavity; and least one electrode on each of the planar surfaces that is electrifiabie to excite at least one vibration mode of the plate, wherein the at least one cavity is not filled with a material having a Young's modulus substantially equal to the Young's modulus of the material from which the place is formed, such that the presence of the at least one cavity shifts a resonant frequency of at least one vibration mode of the plate with respect to the resonant frequency that characterizes the at least one vibration mode in the absence of the at least one cavity.