The aircraft manufacturer is responsible for acoustic certification. Engines make a significant contribution to overall aircraft noise, especially during takeoff, but represent only 50% of the noise during landing, the other half being generated by the airframe, landing gear and control surfaces (slats, flaps, etc.).
Snecma has therefore made noise a key design factor in its engines (and we are also in charge of acoustics within CFM).
Noise is regulated by ICAO standards. The current standard, ICAO Annex 16 Volume 1, Chapter 4 (better known simply as “Chapter 4), took effect on January 1, 2006. Measurements are taken at three points in the flight: flyover (6,500 m from start of roll), sideline and approach. These standards depend on the aircraft’s maximum takeoff weight and number of engines. They are expressed as EPNdB (effective perceived noise in decibels), a noise unit that reflects the specific characteristics of aviation.
However, there are also certain local regulations, based on taxes or even quotas for landing and takeoff slots.
Having long focused on the design of quieter engines, all CFM-powered aircraft now meet these new, stricter standards, and airlines operating these aircraft are not subject to operational restrictions due to noise.
Snecma and its partners have also worked extensively on the improvement of acoustic panels to achieve a significant decrease in noise. We have invested in a number of research projects to meet these goals, including improvements to engine nacelles, in terms of shape and air inlets, an increase in acoustic treatments, better understanding of the sources of internal noise, using powerful software, and studies on active noise control systems, just to mention a few.
Snecma is focused on meeting the ACARE objective of cutting perceived noise in half by 2020, reflecting our commitment to designing even more silent engines in the future. These engines will power aircraft that meet tomorrow’s local and international standards, and keep total noise levels stable despite the strong growth expected in air traffic.