主题：Woven Speakers

刚刚看到的一篇报道，宣称可能是一种喇叭技术的创新。请楼里的高手品评

 

Woven Speakers

Another recent research report may have an impact on audio transducer technology such as headphones, microphones, or, even more speculatively, loudspeakers. Researchers at MIT and Harvard report in Nature Materials on the manufacture of “Multimaterial piezoelectric fibres.” The piezoelectric effect has been used before at audio frequencies, but usually in very inexpensive and poorly performing headphones and microphones typically utilizing bulk piezoelectric crystals. One Japanese company, Take T, uses a piezoelectric film in its tweeters and super-tweeters. (I have no idea what their products sound like, but their website is entertainingly crazy). That's probably because piezo drivers work their best at high frequencies.

The same holds for the fibers described in the far more sober Nature Materials paper. In it, the researchers describe how a cylindrical sandwich shell of selected materials can be drawn into thin fibers with piezoelectric properties. In the illustration, from the outside in, the layers are polycarbonate (PC), carbon-loaded polycarbonate (CPC), and Poly(vinylidene-fluoride-Trifluoroethylene) copolymer (P(VDF-TrFE)). Indium makes up the electrical contacts. The whole assembly is drawn in a furnace (230o C) into fibers more than 100m long. It is the drawing process itself that confers piezoelectric properties on the P(VDF-TrFE) layer.

 

 

此主题相关图片如下：10_10.gif

 

 

Other fiber geometries are possible and the supplement to the main paper illustrates how a flat fiber starting out as a “preform” 32mm in width, 11mm in thickness, and 25cm long is drawn into a fiber about 2000 micrometers (2mm) in width, 600 micrometers thick, and several hundred meters long. It is these fibers, woven into a sheet, that made the cover of the journal.

 

 

此主题相关图片如下：10_11.gif

As in the case of the Sony laser, let's not all go fantasizing about how something fresh out of the laboratory is going to revolutionize audio reproduction (though I wouldn't put it past the folks at Take T to do exactly that). The paper cites fiber tests at frequencies around 1MHz, and the lowest frequency at which the fibers were tested was 6kHz, which is considerably above the crossover region of a typical 2-way speaker. In response to a direct query, one of the scientists (Zhen Wang) told me “like conventional piezoelectric speakers, piezoelectric fibers operate more efficiently at higher frequencies. The acoustic power output under a constant driving voltage grows with frequency. That’s one of the reasons why most piezoelectric speakers are used as tweeters. By doing additional acoustic engineering to the fibers, we could achieve a lower operational frequency. There is no fundamental limit on the low frequency operation, although the output power will be rather low.”

To turn these fibers into a high-fidelity product would require a lowering of the useful operating range as well as some characterization of their distortion properties. Hopefully the latter can be controlled enough for the fibers to be useful in quality audio reproduction. In the meantime, the scientists speculate that fabrics woven from the fibers could be used as a communications transceiver (the fibers' transduction properties go both ways, from electrical to acoustical signals and vice versa). They could form the basis of an “active catheter” capable of accurate pressure and flow measurements in very small blood vessels and of acoustic microscopy inside acoustically opaque organs. Furthermore, since the fibers can be made extremely long, they might be useful in minimally-perturbative sensor meshes for studying large-area distributions of the pressure and velocity fields in “myriads of fluid flow applications.” BP probably would have found such meshes useful in the Gulf of Mexico.

这是一家日本厂搞出来的。

 

http://www.taket.jp/

一楼/二楼里蓝色子体是带链接的，最好都点一下去看看详细的说明。