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© Gerwin Sturm

Swiss team invents acoustic prism

08/08/16Science & Technology

Researchers at EPFL have invented a prism which can split a sound into its constituent frequencies.

While optical prisms, which split white light into the colours of a rainbow, occur in nature in water droplets and other forms, but an acoustic prism has not been found to occur naturally. The EPFL team, led by Hervé Lissek, has developed the prism to split sound using physical properties alone. The prism is a rectangular tube of aluminium with a series of ten carefully-placed cavities separated by membranes along one side. When sound enters the tube, high-frequency components enter the cavities close to the source, while the low frequencies escape through the holes towards the other end of the tube, dispersing the sound. The membranes between cavities vibrate with a delay that depends on the frequency, which also impacts the dispersion angle.

Because of this additional property, the team discovered it was possible to use the prism to locate the source of a sound. By measuring the frequency of an incoming sound, it’s possible to use the dispersion angle, as each corresponds to a particular frequency.

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