A piezo sounder differs in two major ways from a siren : it draws less current and it emits a higher pitched sound.
Piezo sounders are commonly used as pre-alarm devices . They are also used as full alarm sounders in small houses and apartments . The high frequency sound of the piezo is very loud when close up, but does not carry well over long distances. The lower current consumption of the piezo sounder makes it ideal for use with a control panel that provides only limited power to audible devices .