March 28, 2002	Thursday	Muharram 13, 1423

LONDON, March 27: Scientists have discovered structures called “sonic crystals” that can block traffic noise, may be able to transform an unpleasant sound into a pleasant one, and may even have applications in protecting cities from earthquakes, New Scientist magazine reported on Monday.

Francisco Meseguer of the institute of Material Science in Madrid discovered that a minimalist sculpture in downtown Madrid forms a “sound crystal” that can block out sound waves in the same way as tiny photonic crystals, arrays of light altering material, can be used to manipulate waves of light.

Sonic crystals are mostly empty space and can be made of anything from glass spheres to metal rods and are set in a groups so that sound waves can be bounced off the “crystals” and against each other.

In 1995, Meseguer and acoustics expert, Jaime Llinares, from the University of Valencia, realised that by scaling up the tiny spheres of photonic crystals to centimetre-sized shapes to match the size of sound waves, they could bounce the sound waves so that they would interfere and cancel each other out.

They tested their theory on a sculpture by Spanish minimalist Eusebio Sempere with an array of metal bars at close to the right size, shape and spacing and found that the sculpture did block sound.

The possibilities do not end with sound waves, and researchers are toying with the idea of harnessing other waves, such as earth-jolting seismic waves which could be blocked in the same way. In 1999, Meseguer and his colleagues found they could block small seismic waves in a quarry, by drilling a lattice of holes around a test area.—dpa