# Modeling and Analysis of Noise Emission Using Data from Flight Simulators
## 1 Introduction
Despite the development of aircraft that introduce increasingly innovative solutions to reduce emissions, the continuous growth in the number of operations seems to neutralize the positive impact of these solutions [16]. Furthermore, these solutions appear to be effective mostly in from a long-term perspective, as they require many years of extensive research before they can be implemented, i.e., it may take additional years before airlines incorporate these solutions into their fleets [17]. Standardizing the maneuvers performed by departing aircraft may lead to achieving more uniform flight profiles in its initial stages, when the engines are operating at high-power settings and at relatively low altitudes. This may provide an opportunity to optimize the aircraft's initial climb trajectory and, to a certain extent, be a more immediate solution to noise and gaseous emissions in the airport vicinity. In the Doc 8168, the ICAO recommends that commercial operators shall enforce a maximum of two Noise Abatement Departure Procedures to be used during the take-off and climb-out phase of each flight. The recommendation is implemented by the majority of airlines in their respective Standard Operating Procedures, and despite some differences specific to the airline and aircraft type, these procedures can be divided into two basic categories:  
* Procedures that minimize the effect of noise in areas closer to airports (in ICAO's nomenclature--NADP1);
* Procedures that minimize the effect of noise in areas more distant from the airport (in ICAO's nomenclature--NADP2). It is worth noting, that there are no set boundaries between what can be classified as \"distant\" and \"close-in\" areas. Both procedures differ in specific altitudes, at which the crew commences the maneuver of acceleration to a speed that will enable them to clean up the aircraft configuration (typically 250 KIAS (KIAS--Knots of Indicated Air Speed) under 10,000 feet, although individual departure procedures may specify lower values). The simplicity and independence from multiple factors suggest that for specific initial conditions, there may exist solutions that optimize both noise and gaseous emissions, such as \(CO_{2}\). In general, studies have shown that compliance with these procedures allow for savings both in noise and in gaseous emissions [18; 19]. A schematic representation of both procedures is depicted on Figure 1.  
The clean configuration speed, excess thrust produced by engines, climb gradient, and many other performance parameters are closely related and depend on many factors, including the aircraft's mass and atmospheric conditions, such as wind and temperature, which also change with time and altitude. Relationships describing the interplay of thrust and specific aerodynamic forces and moments acting on aircraft are similarly complex. In general, one can describe the maneuver of acceleration to be the issue of optimal trade-off between potential and kinetic energy (e.g., lowering the climb gradient may speed up the acceleration process, which allows for quicker clean-up and saves excess drag generated by flaps, thus saving some fuel). Noise Abatement Departure Procedures are not the only way to mitigate the degree of noise and gaseous emissions. Usually, they are used in conjunction with other methods, such as reduced take-off thrust, Standard Instrument Departures (SIDs), noise preferential runways, or other airport-specific procedures. According to the Directive 2002/49/WE of European Parliament, aerodrome operators are obliged to assess and revise, every five years, current levels of noise pollution in the vicinity of the airport [20]. This process relies on drawing up strategic noise maps, which portray areas that are particularly vulnerable to higher noise levels. These maps usually depict cumulative noise metrics, such as \(L_{DN}\) (day-night average sound level) or \(L_{night}\) (night average sound level) that account for multiple noise events caused by different departing and arriving traffic in a specified timeframe.