When looking for ideas for our first physical computing project, we had a look at nature to see examples of where a plant or animal would react to sound and or vibration, we came across two examples, the first being the millipede, which curls up whenever you walk closely to it.
We then went on to look at the hedgehog for inspiration. The hedgehog curls up into a ball once it feels that is in danger, when a car drives near it, it reacts to the loud noise the car is making and the vibration that the hedgehog feels through its feet from the car driving on the ground near it. I have also noticed that hedgehogs shiver in fear and make a little noise when they are curled up.
From our inspiration, we decided to make a simple device that would react to both sound and vibration as inputs and produce sounds with vibrations as the output.