This video shows a side view of the transparent loudspeaker performing an audio test, where the frequency is ramped up from 20 Hz up to 20 kHz (across the entire audible range). At very low frequencies (initial part of the video) changes in area (with the frequency of the applied audio signal) of the active region of the device are visible. As the frequency rises, out-of-plane vibrations become visible. The wave structure of these vibrations changes as the frequency increases. This video relates to a paper that appeared in the 30 Aug., 2013, issue of Science, published by AAAS. The paper, by Christoph Keplinger at Harvard University in Cambridge, Mass., and colleagues was titled, "Stretchable, Transparent, Ionic Conductors."
[Video courtesy of Christoph Keplinger and Jeong-Yun Sun, Whitesides and Suo Research Groups, Harvard University]