You can do more than roll them down an inclined plane.

Soft-drink cans beat the diffraction limit

The group generated audible sound from a ring of computer speakers surrounding the acoustic ‘lens’: a seven-by-seven array of empty soft-drink cans. Because air is free to move inside and around the cans, they oscillate together like joined-up organ pipes, generating a cacophony of resonance patterns. Crucially, many of the resonances emanate from the can openings, which are much smaller than the wavelength of the sound wave, and so have a similar nature to evanescent waves.

To focus the sound, the trick is to capture these waves at any point on the array.