EPFL scientists have invented a new type of “acoustic prism” that can split a sound into its constituent frequencies. Their acoustic prism has applications in sound detection.Almost 400 years ago, Newton showed that a prism could split white light into the colors of the rainbow, with each colour corresponding to a different wave frequency. Such an “optical prism” relies on a physical phenomenon (refraction) to split light into its constituent frequencies. Now, a prism exists for sound. Hervé Lissek and his team at EPFL have invented an "acoustic prism" that splits sound into its constituent frequencies using physical properties alone. Its applications in sound detection are published in the Journal of the Acoustical Society of America. The acoustic prism The acoustic prism looks like a rectangular tube made of aluminum, complete with ten, perfectly aligned holes along one side. Each hole leads to an air-filled cavity inside the tube, and a membrane is placed between two consecutive cavities. When sound is directed into the tube at one end, high-frequency components of the sound escape out of the tube through the holes near the source, while low frequencies escape through the holes that are further away, towards the other end of the tube. Like light through an optical prism, the sound is dispersed, with the dispersion angle depending on the wave’s frequency. Angular detection by frequency To take the concept a step further, the researchers realized that they could use the acoustic prism as an antenna to locate the direction of a distant sound by simply measuring its frequency. Since each dispersion angle corresponds to a particular frequency, it’s enough to measure the main frequency component of an incoming sound to determine where it is coming from, without actually moving the prism. source - Mediacom
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