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Wednesday, November 2, 2016

3D Acoustic Holograms...

The researchers designed a hologram that projects sound waves with an amplitude pattern shaped like the letter "A". The top images show the simulated field patterns of the amplitude of sound waves at three representative depths. The bottom row shows the actual experimental amplitudes recorded in an anechoic chamber. (Courtesy: Scientific Reports 6 35437)
Topics: Acoustic Physics, Electromagnetism, Holograms, Metamaterials

Researchers in the US have created a printed array of metamaterials that can produce passive 3D acoustic holograms from a simple sound source, such as a single speaker. The device is made up of 3D-printed Lego-like blocks that can be put together in different configurations. The researchers say that their method is cheaper and simpler than other techniques and that they expect it to "open a new realm of holographic acoustic wave manipulation".

A visual hologram manipulates electromagnetic waves in the visible part of the spectrum to create a 3D image. Because sound also travels in waves, it should be possible to create complex 3D fields of sound – acoustic holograms – in a similar way. While visual holograms can be made with physical structures that diffract light, it isn't so easy with sound due to a lack of materials with the required acoustic properties. Generally, acoustic holograms use a transducer array controlled by complex phase shifting electronics.

Physics World: Building-block metamaterials shape 3D acoustic holograms
Michael Allen is a science writer based in Bristol, UK

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