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 and a high frequency domain, a piezoelectric audio device, and a sensor with an alert device employing the speaker are provided. The speaker includes a piezoelectric vibrator including a piezoelectric body formed of a piezoelectric element and a plate-shaped body, the piezoelectric body is attached to a surface of the piezoelectric body in a concentric form, and a film-shaped body is provided around the vibrator to elastically hold the vibrator. The film-shaped body has a coarse and dense portion in a circumferential direction thereof, which has a physically coarse portion, and which can become a mountain or a valley portion or both, and is disposed to correspond to a natural frequency of an in-phase mode wherein antinodes and nodes are formed in a concentric form. The vibrator and the film-shaped body form a sound producing body.