(BEIJING, August 25) -- A 53,000 square-meter sound-proof PTFE membrane structure is being added to the lower levels of the National Stadium.

The stadium, also known as the "Bird's Nest," has two membrane structures. The transparent snow and rain-proof ETFE membrane is installed on the upper levels of the stadium's steel structure, while the cream-colored PTFE membrane hangs on the steel structure to ensure the sound insulation of the stadium itself.

With its ground breaking in December 2003, the stadium is expected to be completed in March 2008. The 91,000-seat building will host the Opening and Closing ceremonies of the Games of the XXIX Olympiad as well as track and field and the football finals.