Enhancing Air Trafﬁc Management and Reducing Noise Impact: A Novel Approach Integrating B ă neasa Airport with Otopeni RO Airport

: Over the years, Bucharest’s Henri Coand ă International Airport has registered a constant and high increase in air trafﬁc, in terms of both passengers and aircraft movements. This paper presents a trafﬁc diversion solution for the Otopeni RO airport, which aims to alleviate air trafﬁc congestion by redirecting a proportion of the planes to the nearby airport at B ă neasa. The primary challenge faced by diversion to B ă neasa Airport is the proximity of residential areas to the runway at distances of less than 300 m, resulting in signiﬁcant noise pollution issues. At Otopeni Airport, the main operators use aircraft equipped with CFM 56 turbo engines; therefore, this study begins with an evaluation of the noise directivity of a CFM aircraft engine via measurement. The data thus collected enabled the identiﬁcation of the dominant frequencies in the acoustic spectrum of the engine noise. A resonant screen solution has been proposed as a solution for B ă neasa Airport, emphasizing the importance of implementing solutions to address the noise pollution faced by those living near B ă neasa Airport, due to its proximity to the residential area. Various conﬁgurations of perforated metal sheets with different perforation patterns were compared to the test performance of solid sheets to optimize noise absorption. Using the impedance tube tests to achieve the highest absorption coefﬁcient, it was determined that the optimal distance between the perforated metal sheets and the resonant screen was 30 mm. Based on the CFM 56 turbo engine noise directivity and the impedance tube tests, a multitude of numerical simulations were conducted using the IMMI software (IMMI 2011). The simulations were performed for two scenarios with and without an acoustic barrier, accounting for the typical conﬁguration of two engines on an aircraft. The results indicate a reduction of 15 dBA with the implementation of a 4-m-high acoustic barrier, in the case of a CFM 56 engine operating at full throttle while the aircraft is on the ground. Through numerical simulations, the optimized resonant screen demonstrated its potential to signiﬁcantly reduce noise levels, thereby enhancing the overall acoustic environment and quality of life for the communities surrounding B ă neasa Airport. The identiﬁed ﬁndings could serve as a basis for further research and the implementation of innovative solutions to manage air trafﬁc and reduce the impact of aircraft noise in surrounding areas.


Introduction
Bucharest, with a population of approximately 2 million inhabitants, is the largest conurbation and the capital city of Romania. The city has a single large airport, intended for both domestic and international flights [1]. Air travel to and from Bucharest represents a significant mode of transportation for tourists and business travelers, who fly to the city from other locations within Romania, as well as to other destinations worldwide via charter flights to Europe and beyond. In countries such as Romania, which lack a developed implement sociological and/or psychological strategies aimed at increasing responsiveness and community engagement, in order to increase acceptance. Effective communication with the public regarding noise is, therefore, crucial for managers and policymakers [25].
Excessive exposure to noise has numerous direct and indirect effects on safety and hygiene. It directly affects our sense of hearing, disrupts sleep, and causes the masking of speech. Otologists consider industrial noise a source of numerous problems related to the ear, such as noise-induced hearing loss, permanent hearing impairment, acoustic trauma, sensorineural hearing loss, tinnitus, etc. Exposure to high noise levels can indirectly affect human psychology and physiology, resulting in an adverse effect on general performance [26]. A number of ailments also have a causal relationship with noise exposure. Figure 1 illustrates the range of effects of noise on humans.
sensorineural hearing loss, tinnitus, etc. Exposure to high noise levels can indirectly aff human psychology and physiology, resulting in an adverse effect on general performan [26]. A number of ailments also have a causal relationship with noise exposure. Figur illustrates the range of effects of noise on humans.
There have been numerous studies conducted on the direct and indirect effects aircraft noise on human health, spanning borders and continents. These studies ha mainly concentrated on examining the impact on individuals living in close proximity domestic and international airports and their surrounding areas.
Aircraft noise causes some of the most damaging environmental effects on everyd life around airports. It can cause numerous known and undesirable problems: sleep pro lems, reduced school performance in children, mental illness, metabolic disease, card vascular disease, etc. [27,28].
The existing literature has documented the direct and indirect effects of noise on ps chosocial health, ranging from auditory to non-auditory associations [29,30]. The hea impacts of noise include noise sensitivity, trait anxiety, hypertension, high blood pressu stroke, heart attack, myocardial infarctions, and arteriosclerotic lesions [31][32][33]. The results of noise exposure on health in areas where aircraft noise was not predo inant showed that exposure to aircraft noise significantly affected subjective health [3 Vieira et al. (2019) [13] quantified aircraft noise annoyance using the psychoacous model. They found that there was a good agreement between subjective listening te and the actual perceived noise level, according to the psychoacoustic annoyance mode An excess of noise above the individualized noise level threshold that causes anno ance or sensitivity to noise has been shown by studies to be associated with increased ris of certain diseases, from sleep disorders to vegetative-hormonal regulation disorders a negative emotional reactions [34]. There have been numerous studies conducted on the direct and indirect effects of aircraft noise on human health, spanning borders and continents. These studies have mainly concentrated on examining the impact on individuals living in close proximity to domestic and international airports and their surrounding areas.
Aircraft noise causes some of the most damaging environmental effects on everyday life around airports. It can cause numerous known and undesirable problems: sleep problems, reduced school performance in children, mental illness, metabolic disease, cardiovascular disease, etc. [27,28].
The existing literature has documented the direct and indirect effects of noise on psychosocial health, ranging from auditory to non-auditory associations [29,30]. The health impacts of noise include noise sensitivity, trait anxiety, hypertension, high blood pressure, stroke, heart attack, myocardial infarctions, and arteriosclerotic lesions [31][32][33].
The results of noise exposure on health in areas where aircraft noise was not predominant showed that exposure to aircraft noise significantly affected subjective health [31]. Vieira et al. (2019) [13] quantified aircraft noise annoyance using the psychoacoustic model. They found that there was a good agreement between subjective listening tests and the actual perceived noise level, according to the psychoacoustic annoyance model.
An excess of noise above the individualized noise level threshold that causes annoyance or sensitivity to noise has been shown by studies to be associated with increased risks of certain diseases, from sleep disorders to vegetative-hormonal regulation disorders and negative emotional reactions [34].
Upon reviewing the effects of airplane noise on people's health, it is crucial to ensure that Baneasa Airport does not become a source of health problems due to airplane noise as its air traffic increases.
Since the number of airplane movements at Otopeni Airport has increased and is expected to continue to increase once flights have resumed after the pandemic period, and due to the fact that the towns around the airport have continuously expanded, the noise pollution levels for local residents near the airport will inevitably become a problem.
A method of decongesting the traffic at Otopeni Airport consists of re-directing part of it to Baneasa Airport; however, it is not only a smaller airport but is also one that is located within the city of Bucharest and is surrounded by houses.
By diverting part of the traffic from the runways, the problem of noise pollution generated by the airport and the problem of overcrowding are solved until the authorities can build a new large-scale airport to serve the capital of Romania-Bucharest.
The objective of this study is to examine the feasibility of reducing noise levels in the vicinity of Otopeni Airport by diverting traffic for international flights that involve large aircraft to Baneasa Airport. However, the proximity of residential areas to the runway at Baneasa Airport poses a challenge, as this may result in excessive noise exposure for nearby residents. In this study, Baneasa Airport was chosen because it is very close to Otopeni Airport and could be a viable solution for reducing congestion at Otopeni Airport, which is the only airport serving the capital of Romania. Besides the obvious economic advantages, having two airports serving Bucharest can offer several advantages and benefits, such as better air traffic distribution, capacity expansion, and more options for airlines to establish routes to different destinations. More importantly, by diverting some air traffic to a second airport, the noise impact on the surrounding communities can be reduced.

Bucharest Henri Coanda Airport and Bucharest Baneasa-Aurel Vlaicu Approach
Currently, the only international airport serving the capital of Romania, Bucharest, is Otopeni International Airport (IATA code: OTP, ICAO code: LROP). Figure 2 shows its location in Otopeni City, Ilfov County, 16 Upon reviewing the effects of airplane noise on people's health, it is crucial to ensure that Baneasa Airport does not become a source of health problems due to airplane noise as its air traffic increases.
Since the number of airplane movements at Otopeni Airport has increased and is expected to continue to increase once flights have resumed after the pandemic period, and due to the fact that the towns around the airport have continuously expanded, the noise pollution levels for local residents near the airport will inevitably become a problem.
A method of decongesting the traffic at Otopeni Airport consists of re-directing part of it to Baneasa Airport; however, it is not only a smaller airport but is also one that is located within the city of Bucharest and is surrounded by houses.
By diverting part of the traffic from the runways, the problem of noise pollution generated by the airport and the problem of overcrowding are solved until the authorities can build a new large-scale airport to serve the capital of Romania-Bucharest.
The objective of this study is to examine the feasibility of reducing noise levels in the vicinity of Otopeni Airport by diverting traffic for international flights that involve large aircraft to Baneasa Airport. However, the proximity of residential areas to the runway at Baneasa Airport poses a challenge, as this may result in excessive noise exposure for nearby residents. In this study, Baneasa Airport was chosen because it is very close to Otopeni Airport and could be a viable solution for reducing congestion at Otopeni Airport, which is the only airport serving the capital of Romania. Besides the obvious economic advantages, having two airports serving Bucharest can offer several advantages and benefits, such as better air traffic distribution, capacity expansion, and more options for airlines to establish routes to different destinations. More importantly, by diverting some air traffic to a second airport, the noise impact on the surrounding communities can be reduced.

Bucharest Henri Coanda Airport and Bucharest Baneasa-Aurel Vlaicu approach
Currently, the only international airport serving the capital of Romania, Bucharest, is Otopeni International Airport (IATA code: OTP, ICAO code: LROP). Figure 2 shows its location in Otopeni City, Ilfov County, 16.5 km north of the center of Bucharest, at 44°34′16″ N, 26°05′06″ E.  The data presented in Figure 3 illustrates the statistics on the movements and passenger numbers at Otopeni Airport [35]. The data presented in Figure 3 illustrates the statistics on the movements and passenger numbers at Otopeni Airport [35].  Prior to 2020, which marked the outbreak of the COVID-19 pandemic, there had been a consistent upward trend in air traffic. This growth prompted proposals for airport expansion or even for the construction of a new airport in the vicinity of the capital to accommodate the surge in aircraft flow. However, a more cost-effective and straightforward alternative is to utilize Baneasa Airport. The airport is surrounded by residential areas in the south, east, southwest, and northeast directions, and by commercial and industrial zones in the north and west areas. The airport's main activity concerns the provision of services, operation, maintenance, repair, development, and the modernization of assets in its ownership or concession to ensure good conditions for the arrival, departure, and ground handling of aircraft from national and/or international traffic, while providing airport services for the transit of passengers, goods, and mail, as well as services of national public interest.
As shown in Figure 4, Baneasa Airport is relatively small. Prior to 2020, which marked the outbreak of the COVID-19 pandemic, there had been a consistent upward trend in air traffic. This growth prompted proposals for airport expansion or even for the construction of a new airport in the vicinity of the capital to accommodate the surge in aircraft flow. However, a more cost-effective and straightforward alternative is to utilize Baneasa Airport. The airport is surrounded by residential areas in the south, east, southwest, and northeast directions, and by commercial and industrial zones in the north and west areas. The airport's main activity concerns the provision of services, operation, maintenance, repair, development, and the modernization of assets in its ownership or concession to ensure good conditions for the arrival, departure, and ground handling of aircraft from national and/or international traffic, while providing airport services for the transit of passengers, goods, and mail, as well as services of national public interest.
As shown in Figure 4, Baneasa Airport is relatively small.  At present, Baneasa Airport is used for international flights featuring smaller aircraft and has substantially lower traffic volumes compared to Otopeni Airport, as substantiated by the data presented in Figure 5 [35]. At present, Baneasa Airport is used for international flights featuring smaller aircraft and has substantially lower traffic volumes compared to Otopeni Airport, as substantiated by the data presented in Figure 5 [35]. At present, Baneasa Airport is used for international flights featuring smaller aircraft and has substantially lower traffic volumes compared to Otopeni Airport, as substantiated by the data presented in Figure 5  As shown in Figure 6, these two airports are located close to each other and could serve the same region. As can be seen in Figure 4, above, Baneasa Airport's runway is very close to nearby houses, and the nearest houses are only 300 m away. Consequently, using it for larger, more powerful aircraft or in high-traffic situations is almost impossible. The primary obstacle that must be addressed to facilitate the utilization of Baneasa Airport in diverting a portion of the air traffic from Otopeni is the issue of noise pollution, stemming from the close proximity of the residential areas to the runway. It is imperative to evaluate the acoustic response of the area to ascertain the feasibility of rerouting the aircraft currently serviced by Otopeni Airport to Baneasa Airport.
The most frequently used aircraft for takeoff and landing at Otopeni Airport in 2021, listed in decreasing order, were B738, A320, A321, AT76, and B737 [37]. Given that most of the aircraft operating at Otopeni Airport are equipped with CFM 56 engines [37], this study will primarily gather data on and examine the noise generated by this particular engine type, since the engines are the primary source of aircraft noise during take-off and landing [38]. As shown in Figure 6, these two airports are located close to each other and could serve the same region. As can be seen in Figure 4, above, Baneasa Airport's runway is very close to nearby houses, and the nearest houses are only 300 m away. Consequently, using it for larger, more powerful aircraft or in high-traffic situations is almost impossible. The primary obstacle that must be addressed to facilitate the utilization of Baneasa Airport in diverting a portion of the air traffic from Otopeni is the issue of noise pollution, stemming from the close proximity of the residential areas to the runway. It is imperative to evaluate the acoustic response of the area to ascertain the feasibility of rerouting the aircraft currently serviced by Otopeni Airport to Baneasa Airport.

Acoustic Solutions for Baneasa Airport
A possible acoustic measure to address the issue in Baneasa Airport is the installation of sound-absorbing panels around the runway to mitigate the impact of noise on nearby residential areas. To design sound-absorbing panels and to conduct numerical simulations, knowledge of the directivity of the CFM 56 engine is necessary.
2.2.1. CFM 56 Acoustic Directivity The first step to improvement is to identify the acoustic directivity of a CFM 56-7D engine, used in the B737 aircraft, during aircraft operation on the ground. This was The most frequently used aircraft for takeoff and landing at Otopeni Airport in 2021, listed in decreasing order, were B738, A320, A321, AT76, and B737 [37]. Given that most of the aircraft operating at Otopeni Airport are equipped with CFM 56 engines [37], this study will primarily gather data on and examine the noise generated by this particular engine type, since the engines are the primary source of aircraft noise during take-off and landing [38].

Acoustic Solutions for Baneasa Airport
A possible acoustic measure to address the issue in Baneasa Airport is the installation of sound-absorbing panels around the runway to mitigate the impact of noise on nearby residential areas. To design sound-absorbing panels and to conduct numerical simulations, knowledge of the directivity of the CFM 56 engine is necessary.

CFM 56 Acoustic Directivity
The first step to improvement is to identify the acoustic directivity of a CFM 56-7D engine, used in the B737 aircraft, during aircraft operation on the ground. This was performed for two operating modes, namely, idle and maximum. For this study, measurements were made with a multi-channel acquisition system, the 01 dB Metravib-Orchestra.
The measurements were taken at 12 different points, as depicted in Figure 7, at intervals of 12.85 degrees. A set of 12 GRAS 40AE microphones was utilized, with a frequency range of 0-25.6 kHz, and an accuracy of class 1. Sensitivities were between 43.9 and 44.3 mV/Pa. The microphones were coupled with 12 GRAS 26CA preamplifiers, with a frequency range of 2-100 kHz and an input impedance of 20 GOhmi and 0.4 pF. The 12 measurement points were positioned 25 m from the source. The data are available from Ref. [39]. After conducting the acoustic measurements, the results were obtained and are presented as a comparative analysis of the 1/3 octave spectra for the idle regime ( Figure  8) and the maximum regime ( Figure 9). After conducting the acoustic measurements, the results were obtained and are presented as a comparative analysis of the 1/3 octave spectra for the idle regime ( Figure 8) and the maximum regime ( Figure 9). After conducting the acoustic measurements, the results were obtained and are presented as a comparative analysis of the 1/3 octave spectra for the idle regime ( Figure  8) and the maximum regime ( Figure 9).  Based on the spectral analyses conducted at each measurement point, noise polar diagrams have been generated that depict the frequency-dependent directivity of the noise source.
In order to create the noise polar diagrams, the 1/1 octave sound power spectra were used for all 12 measurement points for both engine modes. Table 1 presents the spectrum of sound power as a 1/1 octave for idle mode.  Based on the spectral analyses conducted at each measurement point, noise polar diagrams have been generated that depict the frequency-dependent directivity of the noise source.
In order to create the noise polar diagrams, the 1/1 octave sound power spectra were used for all 12 measurement points for both engine modes. Table 1 presents the spectrum of sound power as a 1/1 octave for idle mode.   Table 2 presents the 1/1 octave sound power spectrum for the maximum regime.   Table 2 presents the 1/1 octave sound power spectrum for the maximum regime.

Design of Sound-Absorbing Panels
The novel design of the resonance-absorbent screen will target the area of interes between 1600 Hz and 4000 Hz. The new design will incorporate the benefits of traditiona barriers and resonance-absorbent structures for optimal performance.
The resonance-absorbent structures consist of interconnected resonators, created b perforating holes in a plate mounted at a specific distance from a rigid wall, as shown i Figure 12. By inserting a porous absorbent material into the space between the plate an the wall, the system's absorption efficiency can be significantly improved.

Design of Sound-Absorbing Panels
The novel design of the resonance-absorbent screen will target the area of interest between 1600 Hz and 4000 Hz. The new design will incorporate the benefits of traditional barriers and resonance-absorbent structures for optimal performance.
The resonance-absorbent structures consist of interconnected resonators, created by perforating holes in a plate mounted at a specific distance from a rigid wall, as shown in Figure 12. By inserting a porous absorbent material into the space between the plate and the wall, the system's absorption efficiency can be significantly improved.

Design of Sound-Absorbing Panels
The novel design of the resonance-absorbent screen will target the area of interest between 1600 Hz and 4000 Hz. The new design will incorporate the benefits of traditional barriers and resonance-absorbent structures for optimal performance.
The resonance-absorbent structures consist of interconnected resonators, created by perforating holes in a plate mounted at a specific distance from a rigid wall, as shown in Figure 12. By inserting a porous absorbent material into the space between the plate and the wall, the system's absorption efficiency can be significantly improved. The frequency band of such a system can be calculated using Equation (1) [40]: The frequency band of such a system can be calculated using Equation (1) [40]: where: -D is the distance of the plate from the rigid wall; -f 0 is the frequency of resonance; -λ 0 (m) is the wavelength at resonance.
The frequency of resonance is established by the size of the resonator's neck and the volume of air in the cavity. By adjusting the distance of the plate from the wall and the density of the porous material in the cavity, the frequency band can be broadened to cover up to three octaves.
To ensure low costs for the new absorbent structure, round perforated plates that are widely available on the market were selected and five types of perforated plates were considered for the study, as presented in Table 3. To determine the optimal perforated plate for our application and for the established frequency range of interest, the distance between the perforated plate and the unperforated plate was varied from 10 to 100 mm, increasing in increments of 10 mm, and the resonance frequency and bandwidth of each plate were calculated. The results are presented in Table 4. For each scenario, the bandwidth (Hz) was identical. Based on the above calculations, plate number 1 exhibits the broadest frequency range. To confirm the calculations obtained for plate 1 and acoustically characterize the plate, measurements of the sound absorption coefficient were carried out using an impedance tube (Kundt tube, Figure 13) according to the UNI EN ISO 10534 2 standard [41,42]. Based on the above calculations, plate number 1 exhibits the broadest frequency range. To confirm the calculations obtained for plate 1 and acoustically characterize the plate, measurements of the sound absorption coefficient were carried out using an impedance tube (Kundt tube, Figure 13) according to the UNI EN ISO 10534 2 standard [41,42]. Following the experiments using the Kundt tubes, the absorption coefficient was calculated. The results are presented in the graph displayed in Figure 14.
The comparative analysis revealed that the optimal distance between the perforated plate and the unperforated rigid plate is 30 mm. At this distance, the perforated plate maintains its highest absorption coefficient over the broadest frequency range (1.25 kHz-5 kHz). This frequency range is important to analyze because it includes the resonance frequencies of the auditory canal of the human ear. Additionally, the best absorption coefficient for a frequency of 1.25 kHz-5 kHz (which was identified in the spectra obtained for the CFM56 regime at 100%) was obtained at a distance of 30 mm, as demonstrated in Figure 15. Following the experiments using the Kundt tubes, the absorption coefficient was calculated. The results are presented in the graph displayed in Figure 14. The comparative analysis revealed that the optimal distance between the perforated plate and the unperforated rigid plate is 30 mm. At this distance, the perforated plate maintains its highest absorption coefficient over the broadest frequency range (1.25 kHz-5 kHz). This frequency range is important to analyze because it includes the resonance frequencies of the auditory canal of the human ear. Additionally, the best absorption coefficient for a frequency of 1.25 kHz-5 kHz (which was identified in the spectra obtained for the CFM56 regime at 100%) was obtained at a distance of 30 mm, as demonstrated in Figure 15.  The comparative analysis revealed that the optimal distance between the perforated plate and the unperforated rigid plate is 30 mm. At this distance, the perforated plate maintains its highest absorption coefficient over the broadest frequency range (1.25 kHz-5 kHz). This frequency range is important to analyze because it includes the resonance frequencies of the auditory canal of the human ear. Additionally, the best absorption coefficient for a frequency of 1.25 kHz-5 kHz (which was identified in the spectra obtained for the CFM56 regime at 100%) was obtained at a distance of 30 mm, as demonstrated in Figure 15. The features of the newly designed resonance-absorbent screen, intended to reduce airport noise, are: • a perforated plate, with a thickness of 1 mm × perforation diameter of 2 mm × the distance between the centers of perforations 4 mm; • a rigid unperforated plate, with a thickness of 10 mm, and a weight of 12 kg/m 2 ; • distance between the two plates = 30 mm; • minimum height = 4 m.
The proposed material for the construction of the screen is a transparent plastic (polycarbonate) that possesses highly effective acoustic properties. In addition to excellent sound insulation, it offers high impact resistance, requires no maintenance, and has flame-retardant properties, which prevent fire propagation. It is lightweight and comes in a variety of design options.
Plastic sound-absorbing screens exhibit exceptional resistance to extreme weather conditions at both very low and very high temperatures, without suffering any damage. The proposed resonance-absorbent screen is presented in a schematic form in Figure 16.
The proposed material for the construction of the screen is a (polycarbonate) that possesses highly effective acoustic properties. In sound insulation, it offers high impact resistance, requires no mainten retardant properties, which prevent fire propagation. It is lightwei variety of design options.
Plastic sound-absorbing screens exhibit exceptional resistance conditions at both very low and very high temperatures, without su The proposed resonance-absorbent screen is presented in a schematic Figure 16. Resonance-absorbent screen for mitigating airport noise.

Acoustic Prediction
The estimation of noise reduction was performed using the IM gram. IMMI is fully compliant with the latest European guidance on n guidance document represents internationally agreed best practices modern aircraft noise models. The IMMI program system is a deta software system that also simulates noise events. This program pro calculate noise propagation from various types of sounds. IMMI su data acquisition system used for airports and airfields, which signific speeds up data preparation and input, making the simulation and the of reception points with new input data extremely facile and fast to p IMMI has also been utilized in Ref. [44] and other studies that around airports [45]. IMMI comprises: • Uploading the noise spectrum produced by the CFM56 turbojet e the ground, taking into consideration the directivity and the c contour; • Modeling the designed screen into IMMI, incorporating the abso determined in the laboratory; • Creating the noise contour with the resonance-absorbent screen; Figure 16. Resonance-absorbent screen for mitigating airport noise.

Acoustic Prediction
The estimation of noise reduction was performed using the IMMI prediction program. IMMI is fully compliant with the latest European guidance on noise modeling. This guidance document represents internationally agreed best practices, as implemented in modern aircraft noise models. The IMMI program system is a detailed noise-mapping software system that also simulates noise events. This program provides algorithms to calculate noise propagation from various types of sounds. IMMI supports the standard data acquisition system used for airports and airfields, which significantly simplifies and speeds up data preparation and input, making the simulation and the frequent calculation of reception points with new input data extremely facile and fast to process [43].
IMMI has also been utilized in Ref. [44] and other studies that model aircraft noise around airports [45]. IMMI comprises:

•
Uploading the noise spectrum produced by the CFM56 turbojet engine, measured on the ground, taking into consideration the directivity and the creation of the noise contour; • Modeling the designed screen into IMMI, incorporating the absorption coefficient, as determined in the laboratory; • Creating the noise contour with the resonance-absorbent screen; • Comparing the two contours and assessing the noise reduction.
The objective was to numerically simulate the noise impact produced by the CFM56 turbojet engine (ground operation) and to determine the noise propagation in the adjacent residential area.
The number of buildings and the footprint of each building were determined using Google Maps, then, on the basis of visual observations made on site, the heights of groups of similar buildings in the area of interest were measured with the help of a telemeter.
The sound power spectra (1/1 octave) recorded in dB at the maximum regime, as presented in Table 4, were incorporated into the simulation, assuming a measurement surface area of 1963.50 m 2 . The calculation area was set at 60 m × 60 m, with a grid resolution of 1 m.

Results and Discussion
As shown in Figures 3 and 5, which represent Google Maps captures of the airports, the houses are located close to the runway. Thus, it is necessary to assess the impact of aircraft engine noise on these buildings during the maximum regime and to estimate the noise reduction provided by the proposed solution.
The results are displayed in Figure 17.
The objective was to numerically simulate the noise impact produced by the CFM56 turbojet engine (ground operation) and to determine the noise propagation in the adjacent residential area.
The number of buildings and the footprint of each building were determined using Google Maps, then, on the basis of visual observations made on site, the heights of groups of similar buildings in the area of interest were measured with the help of a telemeter.
The sound power spectra (1/1 octave) recorded in dB at the maximum regime, as presented in Table 4, were incorporated into the simulation, assuming a measurement surface area of 1963.50 m 2 . The calculation area was set at 60 m × 60 m, with a grid resolution of 1 m.

Results and Discussion
As shown in Figures 3 and 5, which represent Google Maps captures of the airports, the houses are located close to the runway. Thus, it is necessary to assess the impact of aircraft engine noise on these buildings during the maximum regime and to estimate the noise reduction provided by the proposed solution.
The results are displayed in Figure 17. To simulate the noise produced by an aircraft during ground operation (taxiing), the source depicted in Figure 17 was duplicated, assuming a mirroring of the directivity To simulate the noise produced by an aircraft during ground operation (taxiing), the source depicted in Figure 17 was duplicated, assuming a mirroring of the directivity vectors. Additionally, the calculation area was expanded to 1000 m × 700 m and the grid resolution was increased to 10 m, then the houses in the neighboring residential area were positioned. The resulting output is shown in Figure 18.
vectors. Additionally, the calculation area was expanded to 1000 m × 700 m and the grid resolution was increased to 10 m, then the houses in the neighboring residential area were positioned. The resulting output is shown in Figure 18. For this study, the area of buildings closest to the runway was selected, as shown in Figure 19. By utilizing the input data described above, a noise contour incorporating the resonance-absorbent screen was obtained, as shown in Figure 20. For this study, the area of buildings closest to the runway was selected, as shown in Figure 19. vectors. Additionally, the calculation area was expanded to 1000 m × 700 m and the grid resolution was increased to 10 m, then the houses in the neighboring residential area wer positioned. The resulting output is shown in Figure 18. For this study, the area of buildings closest to the runway was selected, as shown in Figure 19. By utilizing the input data described above, a noise contour incorporating the reso nance-absorbent screen was obtained, as shown in Figure 20. By utilizing the input data described above, a noise contour incorporating the resonance-absorbent screen was obtained, as shown in Figure 20. By comparing the two noise contours, it is clear that the reduction achieved by incor porating the redesigned resonance-absorbent screen can reach up to 15 dB, depending on the location of the houses. There are no houses that are exposed to more than 65 dBA in the model, according to Figure 20.
This reduction can be further improved by increasing the height of the screen. More over, in areas where houses are closer to the runway, a higher screen height can be used than in those areas where the houses are further away from the runway. It should be noted that the reduction obtained via the prediction software program is consistent with tha obtained through calculation. The difference between the two results is due to the posi tioning of the noise source; in the prediction, the center of the runway is treated as th noise source, while in the calculation, the location closest to the houses is designated a the noise source.

Conclusions and Future Studies
Considering the potential rerouting of aeronautic traffic from Otopeni Airport to Baneasa Airport, this study was conducted based on the fact that most of the aircraft op erating at OTP are equipped with CFM 56-type engines. Thus, the first step of this research involved measuring the directivity of a CFM 56 engine mounted on an aircraft, during both the idling and maximum-load regimes.
The second step involved designing a sound-absorbing panel through the evaluation of various perforated plate configurations via impedance tubes. Using the directivity data a simulation was performed using the IMMI software, with the two engines of an aircraf serving as the acoustic power source and the directivity obtained from the experiments The simulation was performed for the maximum operating regime of the engines when the plane was taking off and was on the ground, assuming a location in the vicinity of th area where the houses are closest to the runway. The subsequent round of simulation was performed by incorporating a panel with the characteristics determined in the labor atory and a height of 4 m. This panel would be made of fireproof and weather-resistan material and would be transparent, avoiding any visual disruptions or alterations to th local landscape for the residents in the area. By comparing the two noise contours, it is clear that the reduction achieved by incorporating the redesigned resonance-absorbent screen can reach up to 15 dB, depending on the location of the houses. There are no houses that are exposed to more than 65 dBA in the model, according to Figure 20.
This reduction can be further improved by increasing the height of the screen. Moreover, in areas where houses are closer to the runway, a higher screen height can be used than in those areas where the houses are further away from the runway. It should be noted that the reduction obtained via the prediction software program is consistent with that obtained through calculation. The difference between the two results is due to the positioning of the noise source; in the prediction, the center of the runway is treated as the noise source, while in the calculation, the location closest to the houses is designated as the noise source.

Conclusions and Future Studies
Considering the potential rerouting of aeronautic traffic from Otopeni Airport to Baneasa Airport, this study was conducted based on the fact that most of the aircraft operating at OTP are equipped with CFM 56-type engines. Thus, the first step of this research involved measuring the directivity of a CFM 56 engine mounted on an aircraft, during both the idling and maximum-load regimes.
The second step involved designing a sound-absorbing panel through the evaluation of various perforated plate configurations via impedance tubes. Using the directivity data, a simulation was performed using the IMMI software, with the two engines of an aircraft serving as the acoustic power source and the directivity obtained from the experiments. The simulation was performed for the maximum operating regime of the engines when the plane was taking off and was on the ground, assuming a location in the vicinity of the area where the houses are closest to the runway. The subsequent round of simulations was performed by incorporating a panel with the characteristics determined in the laboratory and a height of 4 m. This panel would be made of fireproof and weather-resistant material and would be transparent, avoiding any visual disruptions or alterations to the local landscape for the residents in the area.
The comparison showed a reduction in L eq of approximately 15 dB. These simulations indicate that Baneasa Airport could accommodate aircraft with CFM 56 engines without causing additional acoustic impact to the inhabited area surrounding the runway. The noise reduction could be improved further by increasing the height of the panel.
A 15 dB reduction in L eq is considered to be a substantial improvement in terms of reducing the noise impact on those living near the airport. However, the actual impact on the residents would vary, based on factors such as the initial noise levels, the residents' sensitivity to noise, and the duration and frequency of noise exposure. Further assessments are necessary to fully determine the impact.
In the future, we aim to expand this study to include other types of aircraft equipped with different types of turbo engines. Additionally, we plan to conduct a study using different types of sound-absorbing panels. Another research direction will involve simulating aircraft movement on the take-off runway, using specialized software.