Number 196 (Story #3), September 28, 1994 by Phillip F. Schewe and Ben Stein FRACTAL DRUMS are hypothetical structures with which scientists can study what happens when you strike a membrane stretched across a fractal-shaped frame. An example of such a shape is a "Koch snowflake," whose perimeter features an infinite regress of large triangular edges studded with ever smaller triangular edges. Computer simulations performed by Bernard Sapoval at the Ecole Polytechnique in Palaiseau, France show that the waveforms produced on drums with fractal snowflake boundaries (or as fractal as a computer with finite resources can provide) exhibit drastic cusps near the rim, with a consequential damping of the drumhead's movements. This may explain why heavily-indented coastlines seem to soak up the sea's energy more successfully (with less erosion) than smoother coastlines. The indentation effect might even be at work in the way porous silicon (with a myriad of nanoscopic filaments) emits light. (Science News, 17 Sept.)