Audiobooks with paper loudspeakers

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A photo book incorporating the sound of the sea and birdsong, a novel with spoken dialog – this is all made possible by loudspeaker paper and electronics concealed in the cover. Such T-books – where T stands for the German word Ton, meaning sound – can currently be heard at the Frankfurt Book Fair.

Most fairs are already loud enough. Even book fairs. But if the development on display at the CPI booth of the Frankfurt Book Fair (hall 4.0, booth F73) is successful, the future noise level looks set to increase. Not only in the halls of trade fairs, also in living rooms, public transport and – God forbid – supermarkets, drugstores, and the like could all be equally affected.

After years of research, technicians at TU Chemnitz have now introduced the latest generation of their “T-books”. The “T” here has nothing to do with Telecom, but stands for Ton (sound). In other words, the pages of the book are simultaneously loudspeakers and can therefore emit sounds of any kind. Sensors detect which pages are open, and the necessary audio electronics and SD card are concealed in the book’s cover. Naturally, given their frequency response the sound quality has no chance even compared to a kitchen radio. The bass is much too “thin”, but high and medium frequencies are quite well reproduced. And surprisingly loud.

Mass-producible paper loudspeakers

The technology behind it is actually relatively simple. Perfectly ordinary paper is printed with two layers of a conductive organic polymer, which act as electrodes. Between them is the active element, a piezoelectric layer that causes the paper to vibrate, thus exciting the air and producing the sound. The remaining difficulty is primarily that of developing a cost-effective mass production for it.

Two years ago the Chemnitz researchers, in collaboration with the Munich advertising agency Serviceplan, implemented the World Press Photo Foundation’s Yearbook as a T-book. This audio-tome weighed more than 3kg, which was mainly down to the battery. Unsurprisingly, this small-series product ultimately proved too unwieldy and too expensive.

That is why the original method of producing individual sheets is to be superseded by a roll process, which will optimize both performance and appearance of paper loudspeakers. In future, the electronic components will also be printed. This will considerably increase the efficiency of the entire manufacturing process and open up mass markets such as photobooks. In future, for example, instruction leaflets could read themselves aloud, and books could become accessible to blind people. The opposite effect is also possible – loudspeaker paper could be used to construct a force sensor or a microphone. What is called the “direct piezoelectric effect” responds to an elastically deformed solid by producing a voltage. This means that there are any number of useful applications, not necessarily things like chatty packaging, singing wallpaper and similar strident marketing hype.

T-book (Image: TU Chemnitz)

The batteries, SD card and control electronics of the T-book are concealed in the cover. (Image: TU Chemnitz)