Washington, D.C. (January 11, 2011) -- Whether the object of attention is a novel aspect of the universe or an enigmatic and distant colleague, listening is key to nearly any effort to seek understanding. And not just with your ears. Spectroscopy, the study of how atoms absorb and emit electromagnetic radiation, is like listening, too. The technique is central to a range of physics experiments and can be thought of as an attempt to filter out useful information from what various sensors and detectors often first "hear" as undifferentiated electromagnetic noise.
Now, a new twist on spectroscopy, described in the American Institute of Physics' in journal Review of Scientific Instruments, allows for an unprecedented level of such filtering -- one that could transform everything from the search for extraterrestrial intelligence to super-sensitive spy gear to scan hotel rooms for hidden microphones or cameras.
The technique was demonstrated on the slice of the electromagnetic spectrum containing frequencies on which terrestrial radio stations broadcast music. Current spectroscopy techniques can take such radio signals and tell you, in effect, the average volume and pitch of each moment of the music. However, if a given moment is made up of several notes played simultaneously -- a chord, say -- that fact is more or less invisible.
Or rather, it was invisible before the recent work of doctoral student Sebastian Starosielec and professor Daniel Hägele, both at Germany's Ruhr University Bochum. By stitching together a MHz-sampling card -- a radio-frequency version of a sound card -- and a multi-core graphics CPU, the two combed through a broad band of the radio spectrum in extra-fine detail. Their technical achievement, which determined in real time correlations among many thousands of pairs of frequencies, for the first time makes it easy to distinguish between a soloist and an ensemble based only on analysis of spectra.
Beyond the search for E.T. and illicit bugs, the technique could prove useful "for detecting anything that is not pure noise," says Hägele. Other applications could include better measurements of various physical systems, particularly in atomic and solid state physics, and the possibility of better communication signal recovery to be used on and off the planet's surface.
Hägele gives the following example to illustrate the power of the the technology: Imagine a TV show was broadcast daily from Mars, and the signal was received, along with a vast amount of background noise, here on Earth. After a few days "we would be able to reconstruct the show's introduction, including the theme song and images, just from spectroscopic data," he says.
The article, "Two-dimensional higher order noise spectroscopy up to radio frequencies" by Sebastian Starosielec, Rachel Fainblat, Jörg Rudolph, and Daniel Hägele appears in the journal Review of Scientific Instruments. See: http://link.
This work is supported by the German Research Foundation and Germany's Excellence Initiative.
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REVIEW OF SCIENTIFIC INSTRUMENTS
Review of Scientific Instruments, published by the American Institute of Physics, is devoted to scientific instruments, apparatus, and techniques. Its contents include original and review articles on instruments in physics, chemistry, and the life sciences; and sections on new instruments and new materials. One volume is published annually. Conference proceedings are occasionally published and supplied in addition to the Journal's scheduled monthly issues. RSI publishes information on instruments, apparatus, techniques of experimental measurement, and related mathematical analysis. Since the use of instruments is not confined to the physical sciences, the journal welcomes contributions from any of the physical and biological sciences and from related cross-disciplinary areas of science and technology. See: http://rsi.
The American Institute of Physics is a federation of 10 physical science societies representing more than 135,000 scientists, engineers, and educators and is one of the world's largest publishers of scientific information in the physical sciences. Offering partnership solutions for scientific societies and for similar organizations in science and engineering, AIP is a leader in the field of electronic publishing of scholarly journals. AIP publishes 12 journals (some of which are the most highly cited in their respective fields), two magazines, including its flagship publication Physics Today; and the AIP Conference Proceedings series. Its online publishing platform Scitation hosts nearly two million articles from more than 185 scholarly journals and other publications of 28 learned society publishers.