3D print a functional speaker
The secret involves using electrostatic loudspeaker technology that actually dates back to the 1930s, instead of the electromagnetic approach that is far more common these days. The special 3D-printing process creates layers of electrodes and insulators in the object, which vibrate when a current is applied.
The sound quality never really comes close to what you’d get from the delicate paper cones used in your home stereo’s speaker. But, depending on the size of the object, they can be extremely loud. And they’re durable too, meaning you could 3D-print an interactive toy for kids that makes noises when placed on a conducting base, and not have to worry about them destroying it minutes later.