a hermetically sealed metal detector includes a plastic housing with an integrally formed diaphragm having a predetermined area and a thickness that enables vibration thereof by an internal acoustic transducer . an alert signal audibly drives the transducer in response to a metal detector circuit . the acoustic transducer is positioned to align the transducer output port adjacent to the interior surface of the diaphragm , which enables coupling of the acoustic signal through an air gap to vibrate the diaphragm . a cover is disposed about the diaphragm on the exterior of the housing . the cover has a vent formed therethrough for enabling passage of the acoustic energy to the exterior of the housing . light and battery hermetic sealing are also presented .