That’s it. That’s the post.
That’s one of the reasons some advertising and ATMs have switched to panel speakers, there’s no requirement for vent holes for the sound to escape, so it’s pretty much impossible to vandalise. A physical part of the gas pump or ATM becomes the speaker, by being energised by an audio exciter stcuk to the back side of it. If you see something producing sound with no obvious speaker holes, it’s probably using a DML exciter. It’s actually a very interesting technology, a shame it’s being used in advertising.
Surely slathering the surface with two-part epoxy would stop it from making noise?
That could make it louder. I’ve built my own set of DML panel speakers, and coating the outside of the panels in a coat of PVA glue enhanced the high frequency sound. If there’s good connection between the epoxy and the surface, and the exciter is powerful enough to energize it with the extra mass of the epoxy, it will still work. Some people even coat their panels in expoy to try enhance the sound in a similar manner to coating in PVA glue. You would have to get the epoxy jammed in on the side with the exciter, which is usually not accessible.
