PSU Magazine Fall 1993

Using acoustic resonance spectroscopy, this physics grad is making waves. By Valerie Brown Dipen Sinha PhD '80 or many, physics brings to mind imposing arrays of mysterious particle acceler– ators and supercolliders constructed with billions of tax dollars. Or it is seen as a rarefied intellectual pursuit that only occasion– ally touches the lives of real people with real problems. A PSU physics graduate is rurning these assumptions upside down. He tinkers with new ideas and inexpensive materials to devise new technologies with immediate social impact. Oipen inha received his physics doctorate in 1980 from PSU's Environ– mental Sciences and Resources Pro– gram. Today, a a staff member in the Electronic Materials and Device Re– search Group at the Los Alamos (New Mexico) National Laboratory, Sinha is pioneering innovative theory and tech– nology that has already resulted in two new processes of direct human benefit. S inha's current interest is resonance. There are as many kinds of resonance as there are wave forms– electric, acoustic, magnetic, and so forth. For the moment Sinha is focus– ing on the resonance properties of sound waves. About three years ago, he came up with an idea to u e acoustic resonance spectroscopy (ARS) to determine the content of mi sile war– heads without having to open them up. The device is now standard operating equ ipment for international disarma– ment verificat ion of chemical weapons. Sinha has recently applied the same technique to determining whether chicken eggs are infected with salmonella bacteria. This project earned him the 1992 Popular Science 100 Award for the most imaginative new technology of the year. At least 50,000 Americans contract salmonella poisoning every year, and eggs are a principal source of the infection. Acoustic resonance spectroscopy is based on the simple idea that all objects vibrate at a characteristic set of frequencies. A tuning fork, for example, will produce a fairl y pure musical note when struck. Most other objects have a more comp licated "signa– ture" or "acoustic fingerprint." Using ARS, it's possible to discover the acous– tic fingerprint of almost any object. A frequency synthesizer sends vibration into the object through a transducer. Another transducer picks up the result– ing resonance and loads it into a com– puter software program that ana lyzes its patterns. When a baseline reading of an object is determined, variations or anomalies in specific examples can be used to diagnose problems. ince a warhead loaded with conventional weapons will produce a signature that looks very different from one conta ining nerve gas or other chem ica l , the technique is extremely FALL 1993 7