![science surprises](../web_assets/tophead_surprises.gif)
![photo of mariko with a plastic strip](../web_assets/sci_surprise/407_surprise.jpg)
![talking strip!](../web_assets/sci_surprise/407_title.gif)
A simple long, thin strip of plastic has a series of ridges along one side. Pull the strip through your thumb and index finger, with your finger nail edge running over the tops of the ridges. You hear a funny hum that sounds like human speech.
![why?](../web_assets/sci_surprise/title_why.gif)
Sound is caused by something vibrating in the air. The ridges in the plastic strip make the strip vibrate when rubbed, making a humming sound. If the ridges have the proper depth and spacing, the humming noise can be made to mimic the sound of human speech.