A COMPUTER model that reproduces the tinkling of a piano promises to help restorers of antique instruments choose the best materials.
Modern materials are often more durable and less prone to insect infestation than the original ones. But replacing worn parts with new materials can alter the sound of an instrument 鈥� something conservators are keen to avoid. This is where a model developed by physicist Nick Giordano at Purdue University in West Lafayette, Indiana, comes in handy.
Giordano has built a computer model that takes information about a piano鈥檚 size and the materials making up its strings and soundboards to calculate the pattern of vibration of the piano strings. The results are used to make an electronic audio file.
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For a long time Giordano wasn鈥檛 satisfied with the unrealistic sound his model generated, but now he has added extra code to model the effect of the pads that cover the hammers striking the strings.
In modern pianos, these pads are made of felt, which does not vibrate in the same way as the strings or soundboards. Felt is hysteretic, meaning that the rate it compresses when a key is struck affects the way it decompresses as the hammer moves free of the string. This changes the forces acting on the string and gives a modern piano its distinctive sound.
Unlike the computer models that power commercial electronic keyboards, his is based entirely on physics. 鈥淚 would say I really understand what it takes to make a piano,鈥� he says.
This makes it possible to predict the effect of changes in materials on the sound of an actual piano. Giordano is using his model to evaluate materials that might replace the deerskin hammer pads on an English grand piano from the 1820s. Obtaining newly tanned deerskin is one option but Paul Storch, a senior conservator at the Minnesota Historical Society in St Paul, says it鈥檚 not necessarily the best because leather hardens and crumbles over time. Instead of insisting on the same materials as the original, it is better to restore musical instruments so you can play them, he says.