A panel-mountable audible and visual warning device comprising a main housing and a cap thereon, the device configured to have the main housing fit into a hole in the face of a mounting panel and to have the front wall and side wall of the cap external to the panel when the device is operably mounted therein, with the cap containing a piezoelectric transducer and at least one LED as a modular subassembly which is attached to the main housing. The cap and transducer together define an audio-frequency resonant cavity, and the cap has the LED(s) mounted therein in a position in front of the panel face in use and behind and radially outward of the transducer so as to emit light directly forward past the transducer.