"Carbon nanotube speaker" will come out
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Andrew Barnard and his colleagues revisited this ancient idea 100 years ago. This type of loudspeaker, called a thermoacoustic or thermoacoustic loudspeaker, uses a material that oscillates rapidly between cold and hot to produce sound. .
In 1917, Harold Arnold and IB Crandall of the American Telephone and Telegraph Company and Western Electric Company claimed that they could produce sound by connecting both a direct current and an alternating current to a very thin platinum foil. This can be used to discard the conventional loudspeakers. Bulk electromagnet design that stimulates vibration. However, the problem is that the sound produced by this method is not loud, and the frequency response is not enough to copy the speech, so this idea was put on hold for nearly a century.
The idea was again proposed in 2008 when a Chinese team discovered that they were able to extract the thermoacoustic from thin slices made from carbon nanotubes (CNTs). The wall thickness of these nanotubes is only one atom thick and they are purely composed of carbon.
This material is very stable and is a very good thermal conductor. This is the condition needed to finally realize this idea and create a thin speaker. Making carbon nanotubes produce sound is completely different from producing good sound in the human hearing range. Carbon nanotubes may have very valuable applications, such as sonar. However, it is not yet clear whether they can produce a high-fidelity sound in the room where you live.
And that's what Barnard and his colleagues have been trying to assess. One way to improve the sound output is to use a gas with a lower heat capacity than air, such as an inert gas, around the carbon nanotube sheet, so that a large temperature change can be generated with a lower energy input to generate the gas pressure. Barnard and colleagues said that this may be the best way to improve the performance of this device.
In order to transfer sound vibrations from the inert gas to the air, we need to use a flexible membrane to separate the gas from the air. Barnard and his colleagues considered that a high-powered carbon nanotube speaker is achievable, but this is not easy. Carbon nanotube films are likely to need to be isolated by helium gas, which may bring a series of challenges.
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