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A Fusion of Audio Technology and Physics

Photo: John Geraghty, working at a NIST lab.

John Geraghty, a senior at American University with a passion for both audio technology and physics had the opportunity to further both interests last summer at the National Institute for Standards and Technology (NIST). NIST, our nation’s first physical science research laboratory, gives budding scientists like Geraghty a chance to explore advanced fields of science, with its unique Summer Undergraduate Research Fellowships program (SURF). The program lets undergraduate students do cutting-edge, hands-on research through assignments overseen by an NIST researcher. Students applying for the SURF program can choose to intern in one of NIST’s six laboratories: the Material Measurement Laboratory, Physical Measurement Laboratory, Engineering Laboratory, Information Technology Laboratory, Center for Nanoscale and Science Technology, and NIST Center for Neuron Research. Once 130 students are chosen, they spend their summer at NIST facilities in Gaithersburg, Maryland. 

For his internship, Geraghty worked on the transverse motion of the main induction coil in the Electronic Kilogram Experiment, a project with a goal of redefining the mass standard. Currently, mass is measured in terms of a physical object: the kilogram, the last base unit in the International System of Units, which is not defined in terms of fundamental constants and quantum references. Because mass changes every year, the physical constant is an inaccurate way to measure it, so Geraghty’s project worked to improve the measurement of Plank’s constant, the relationship between the energy of a particle and the frequency of its wave. Improving this measurement would provide an alternate definition of the mass standard by utilizing a watt-balance system. A watt-balance system is the ratio of mechanical power to electrical power using an induction coil to generate voltage in one mode and an electrical force to balance the acceleration of gravity on a mass in the second mode. Variability of the induction coil must be measured to compensate for misalignment. 

To tackle this measurement problem, Geraghty was to create a lock-in amplifier, which creates a pure sound by eliminating background noises. Before even attempting to develop the amplifier, however, Geraghty had to spend time acclimating himself to a graphical programming environment called LabVIEW, which scientists and engineers use in developing test, measurement, and control systems. Removing unwanted noises fixes many of the problems from the previous system, while increasing the resolution of the detection program. Geraghty’s work on the amplifier was central to the project, because it allowed for precision lacking in previous measurements. He did not have enough time to finish his project, but others are continuing the work and data collection. 

Geraghty spent his days mostly working on the many facets of developing the lock-in amplifier, which furthered his interests in the audio and physics realms. Even more important, though, was the opportunity to study under an NIST researcher, who helped him understand the complexities and importance of his research at the institute. Geraghty also attended weekly talks given by prominent speakers on topics ranging from robotics to Teach for America. At the end of the program, SURF students presented their projects.

Geraghty thanked professors in the Department of Physics for giving him the opportunity to intern at NIST and for encouraging students to apply for every internship opportunity available and supporting their interests in general. 

Since November 2009, Geraghty has been designing audiovisual systems for AU, installing its new recording studios, maintaining the equipment, and serving as assistant studio manager. He belongs to American’s chapters of the Society of Physics Students and the Audio Engineering Society. His involvement in physics and audio technology will continue this summer with an internship at an architectural acoustics company, allowing him yet another opportunity to follow his passions.