Relationship between noise levels and emissions from aircraft transitions and further considerations for noise reduction

Over the past 30 years, aircraft single-event noise levels have been reduced by approximately 10 dB or more. This is due to ICAO's Balanced Approach source control measures (Annex 16) strengthening standards from Chapter 3 to Chapter 4 and then to Chapter 14. Currently, newly manufactured aircraft comply with the latest Chapter 14 standards. Although they are naturally quieter than previous types, the rate of aircraft compliant with the new standards is increasing year by year, and eventually the new standards will account for most of the aircraft in the market. On the other hand, it is necessary to consider not only noise but also air pollutant emissions from aircraft that affect human health. In this study, the relationship between aircraft noise and engine emissions certification values was examined. The ICAO established an engine emissions certification system addressing emissions like NOx, CO, HC, and PM. While noise, HC, and CO have decreased with each generation, the trends for PM and NOx were unclear. High-temperature combustion reduces noise, HC, and CO, but increases NOx.PM generation varies significantly with combustion temperature and combustor shape. Therefore, while new standards for noise are desirable for further reductions, NOx and PM emissions need separate regulations.