PIEZOELECTRIC SPEAKER, PIEZOELECTRIC AUDIO DEVICE EMPLOYING PIEZOELECTRIC SPEAKER, AND SENSOR WITH ALERT DEVICE ATTACHED

摘要

A piezoelectric speaker having a high sound pressure level in a low-frequency domain and a high-frequency domain, a piezoelectric audio device, and a sensor with an alert device attached employing the piezoelectric speaker are provided. A piezoelectric speaker 1 of the invention includes a piezoelectric vibrator 2 including a piezoelectric body 21 formed of a piezoelectric element and a plate-shaped body (plate) which has a larger diameter than the piezoelectric body 21 and which is attached to a surface of the piezoelectric body 21 in a concentric form, and a film-shaped body 3 that is provided around the piezoelectric vibrator 2 so as to elastically hold the piezoelectric vibrator. The film-shaped body 3 has a coarse and dense portion in a circumferential direction thereof, which has a physically coarse portion, and which can become a mountain portion 3M or a valley portion 3V or both, and is disposed so as to correspond to a natural frequency of an in-phase mode wherein antinodes and nodes are formed in a concentric form. The piezoelectric vibrator 2 and the film-shaped body 3 form a sound producing body.