In his life-long career pursuing, Prof. Dah-You Maa as an acoustics giant contributed greatly in many areas of acoustics, not only in acoustical research and development, but also in the promotion of acoustical education, application and legislation.
Prof. Maa had presented a simplified method for calculation of normal modes for room acoustics, invented micro-perforated panel absorbers and micro-perforation jet mufflers, given a formula of jet noise power via air pressure, acoustically designed the first and biggest Congress Hall, built the first set of acoustical laboratories, and established the acoustical standard system in China. He had also supervised tens of postgraduate students working in environmental acoustics, building acoustics, speech signal processing, nonlinear acoustics, and active noise control.
For the normal mode distribution in room acoustics, Prof. Maa’s prominent contribution in China was that he was appointed as the chief acoustical architect to build the great People's Congress Hall in 1959. However, acoustic treatments and appropriate parameters in existing halls offered little help in such a huge and stately hall. Even so, Prof. Maa solved the problem through an integral consideration of acoustical treatments and electroacoustical systems. Measurements in the completed hall suggested that the expected requirements were well fulfilled and the acoustical characteristics were completely accepted by listeners.
As well, one of Prof. Maa’s notable contribution to micro-perforated panel absorber (MPA) was conducted in 1993. The Fraunhofer Institute of Bauphysics used a well designed and fabricated MPP in the plenum of the Deutscher Bundestag in Bonn. The congress hall was designed and built with a totally transparent and round glass wall, which brought a disaster in the room acoustics and audio engineering. The MPA technique cancelled the echoes from the wall without any influence of the transparency and the shape. The Germans thought that it was Prof. Maa's theory helped them to present and complete the solution, and gave a Gold Medal of the Fraunhofer Society of Germany to Prof. Maa in 1997.
On July 17, 2012, Prof. Maa left us forever. But his career continues in the Institute of Acoustics, Chinese Academy of Sciences, in the Acoustical Society of China, in the Acta Acustca Journal, in the Acoustical Standard Committee of China, and in all those acoustical careers he started, in as well as the friendship he established among the acousticians in China and all over the world.
The work has been published online: http://www.engineeringvillage.com/controller/servlet/Controller?CID=FullTextLink&docID=cpx_535b5813f77f14011M5aaa2061377553 and on Proceedings of Meetings on Acoustics (POMA - ICA 2013 Montreal) (Vol.19, June 2013, pp. 015060, 5 page).