Play the "Imperial March" on a fast switching valve
It seems that the fad of using floppy drives to make music has shifted over to industrial components - and this next example by Arduino forum member "kerimil" could be the start of a whole new method. Using an Arduino and the tone library, a Festo fast switching valve can be activated and deactivated at such a speed that the resulting sound is quite effective. It's a little crazy, but it works - (and watch the battery on the table move from the vibration) for example:
The code is very simple, and can be found here. And we're on twitter and Google+, so follow us for news and product updates as well.
It can be used as a noise-maker driven by your microcontroller for audible feedback of events, and it can also be used as a knock-detector input to sense events and react to them. Includes a built-in 1M resistor to allow the piezo element to detect shocks. For more information and to order, please visit the product page here.