In the early 1950s, aircraft noise was considered as one of the environmental noise impacts when turbo-jet engines were used to power aeroplanes. Thus, the aircraft noise issue was dominated by jet noise (i.e. a propulsive noise). However, in the early 1970s, the airframe of the aircraft itself has become the major source of noise after development of quieter engines (e.g. turbofan engines with high bypass ratios) [1]. Landing gears (LGs) are among the main noise sources generated during the approach-to-land phase of flight compared with the other airframe components [2, 3]. Since the number of people who live near...