In the past two decades, modal analysis has become a major technology in the quest for determining, improving and optimizing dynamic characteristics of engineering structures. This technology has not only been recognized in Mechanical and Aeronautical Engineering but also has discovered its profound applications in Civil constructions of buildings and bridges. To appreciate its significance in the modern engineering arena and its potential for future science and technology, it is appropriate to capture some of the background facts which will help to underline this unique technology.The use of...