NASA subsonic jet transport noise reduction research

Although new jet transport aircraft in today's fleet are considerably quieter than the first jet transports introduced about 40 years ago, airport community noise continues to be an important environmental issue. NASA's Advanced Subsonic Transport (AST) Noise Reduction programme was begun in 1994 as a seven-year effort to develop technology to reduce jet transport noise 10dB relative to -1992 technology. This programme provides for reductions in engine source noise, improvements in nacelle acoustic treatments, reductions in the noise generated by the airframe, and improvements in the way aircraft are operated in the airport environs. These noise reduction efforts will terminate at the end of 2001 and it appears that the objective will be met. However, because of an anticipated 3-8% growth in passenger and cargo operations well into the 21st century and the slow introduction of the new noise reduction technology into the fleet, world aircraft noise impact will remain essentially constant until about 2020 to 2030 and thereafter begin to rise. Therefore, NASA has begun planning with the FAA, industry, universities and environmental interest groups in the USA for a new noise reduction initiative to provide technology for significant further reductions.