A panel-mountable audible and visual warning device having an internal volume control shutter within a resonant cavity defined by the device housing and a sound generating element within the housing. Another embodiment has a cap on a main housing which fits into a hole in a mounting panel, with the cap external to the panel, the cap having multiple LEDs mounted therein in front of the panel face and behind and radially outward of a piezoelectric transducer so as to emit light directly forward past the transducer. Another cap embodiment has a piezoelectric transducer, LEDs, and a pushbutton switch mechanism including a movable surface portion of the cap's front wall and an internal set of switch contacts operably connected thereto. A control circuit can partially disable the alarm signaling function, such as by muting the transducer but continuing to energize the LEDs in response to actuation of the switch.