E-Mail IMAGE: The phononic crystals are made by artificially placing the acrylic posts in the special pattern. view more Credit: The University of Hong Kong The perfect transmission of sound through a barrier is difficult to achieve, if not impossible based on our existing knowledge. This is also true with other energy forms such as light and heat. A research team led by Professor Xiang Zhang, President of the University of Hong Kong (HKU) when he was a professor at the University of California, Berkeley, (UC Berkeley) has for the first time experimentally proved a century old quantum theory that relativistic particles can pass through a barrier with 100% transmission. The research findings have been published in the top academic journal