A stack light with a light section having a housing with a plurality of at least partially translucent side walls and having a plurality of opposing light sources on longitudinally opposite ends of the housing to produce a very even blended light. A stack light system with one or more such light sections also includes a sound section having a hollow housing and a set of interchangeable acoustic chambers configured for insertion into the hollow housing, each chamber including a piezoelectric transducer and having a side wall structure configured to abut an inner side wall surface of the hollow housing, the chamber, transducer and housing together defining a resonant cavity. In one embodiment, an acoustic chamber has a longitudinally extending side wall and a substantially closed end wall, the side wall having adjacent the end wall a plurality of wide lateral openings spaced apart along its perimeter, the openings each having a width in the range of approximately 8-25% of the wavelength of the piezoelectric transducer's fundamental frequency.