Aircraft Noise Modeling Research Articles

A large-scale validation study of aircraft noise modeling for airport arrivals.

In the U.S., the Federal Aviation Administration's Aviation Environmental Design Tool (AEDT) is approved to predict the impacts of aircraft noise and emissions. AEDT's critical role in regulatory compliance and evaluating the environmental impacts of aviation requires asking how accurate are its noise predictions. Previous studies suggest that AEDT's predictions lack desired accuracy. This paper reports on a large-scale study, using 200 000 flight trajectories paired with measured sound levels for arrivals to Runways 28L/28R at San Francisco International Airport, over 12 months. For each flight, two AEDT studies were run, one using the approved mode for regulatory filing and the other using an advanced non-regulatory mode with exact aircraft trajectories. AEDT's per aircraft noise predictions were compared with curated measured sound levels at two locations. On average, AEDT underestimated LAmax by -3.09 dB and SEL by -2.04 dB, combining the results from both AEDT noise-modeling modes. Discrepancies appear to result from limitations in the physical modeling of flight trajectories and noise generation, combined with input data uncertainties (aircraft weight, airspeed, thrust, and lift configuration) and atmospheric conditions.

An Experimental and Analytical Approach to Evaluate Transponder-Based Aircraft Noise Monitoring Technology

Aviation is a vital modern transportation sector connecting millions of passengers globally. Sustainable aviation development holds substantial community benefits, necessitating effective management of its environmental impacts. This paper addresses the need for an accurate and cost-effective aircraft noise monitoring model tailored to non-towered general aviation airports with limited resources for official air traffic data collection. The existing literature highlights a heavy reliance on air traffic data from control facilities in prevailing aircraft noise modeling solutions, revealing a disparity between real-world constraints and optimal practices. Our study presents a validation of a three-stage framework centered on a low-cost transponder unit, employing an innovative experimental and analytical approach to assess the model’s accuracy. An economical Automatic Dependent Surveillance-broadcast (ADS-B) receiver is deployed at Purdue University Airport (ICAO Code: KLAF) to estimate aircraft noise levels using the developed approach. Simultaneously, a physical sound meter is positioned at KLAF to capture actual acoustic noise levels, facilitating a direct comparison with the modeled data. Results demonstrate that the developed noise model accurately identifies aircraft noise events with an average error of 4.50 dBA. This suggests the viability of our low-cost noise monitoring approach as an affordable solution for non-towered general aviation airports. In addition, this paper discusses the limitations and recommendations for future research.

Validating aircraft noise models: Aviation environmental design tool at Heathrow

Aircraft noise models are fundamental tools for noise abatement, control, enforcement, evaluation, and policy-making. Validation of aircraft noise models is necessary to ensure their reliability and credibility, particularly given their significant impact on society, the economy, and public health. However, validating such models is often a complex undertaking, and an acceptable validation methodology still needs to be developed. In this study, the Federal Aviation Administration's (FAA) Aviation Environmental Design Tool (AEDT) aircraft noise model is validated by correlating the calculated and measured noise levels for a specific aircraft flying in a particular flight path at Heathrow Airport. The validation results suggest that the AEDT noise model estimates the actual noise level quite accurately for landings, with a variation less than 2 dB(A), but might be inaccurate for takeoffs for certain aircraft types, with variations reaching 10 dB(A), resulting in a considerable difference between the measured and calculated noise levels.

Study on noise calculation method considering gear and flap conditions during aircraft landing

Looking at recent aircraft noise by component, engine noise has become quieter, while aerodynamic noise such as airframe noise, gear, and flap noise has become relatively louder. Gradually, it has become necessary to take aerodynamic noise into account appropriately. Therefore, using the regression calculation results of aircraft noise by J-FRAIN, we examined to modify performance data and Noise-Power-Distance (NPD)data, which represent component changes consistent with the AERC model, an existing aircraft noise model in Japan. For performance data, gear and flap parameters were added to the already used altitude, speed, and thrust. For NPD data, correction NPD data were prepared for the gear and flap changes using the J-FRAIN calculation results. Using these data, noise calculations were performed considering gear and flap status during aircraft landing. In addition, aircraft landing noise was measured under a flight path of about 30 km around Narita Airport in Japan to confirm the validity of the noise calculation results. Some measured aircraft gear and flap status were obtained and the results of the matched noise calculations were compared with the measured noise.

Standardization of modelling methodology for aircraft noise exposure contours

Aircraft noise exposure contours are important tools for land-use planning around aerodromes. They inform local governments and stakeholders as to the acoustic impacts of aircraft operations on areas surrounding the airport. This information is considered when defining municipal zoning and building regulations. While noise contours are often regarded as concrete guidance identifying the suitability of an area for noise sensitive development, their prescribed modelling methodology is imprecise and non-standardised. A vague description such as the yearly day night level or 95th percentile day is typically mandated by overseeing authorities which leaves ambiguity in terms of the various specific input parameters. This can result in differing noise contour outputs, which in turn can cause conflict, especially between stakeholders with competing interests. This research highlights the need for better standardization and guidance for aircraft noise exposure contour modelling. It further demonstrates how varying interpretations of modelling methodologies can alter the input parameters of an aircraft noise model and significantly impact the outputs.

Aircraft noise in situations with grazing sound incidence-Comparing different modeling approaches.

Current best-practice aircraft noise calculation models usually apply a so-called lateral attenuation term, i.e., an empirical formula to account for sound propagation phenomena in situations with grazing sound incidence. The recently developed aircraft noise model sonAIR features a physically based sound propagation core that claims to implicitly account for the phenomena condensed in this correction. The current study compares calculations for situations with grazing sound incidence of sonAIR and two best-practice models, AEDT and FLULA2, with measurements. The validation dataset includes on the one hand a large number of commercial aircraft during final approach and on the other hand departures of a jet fighter aircraft, with measurement distances up to 2.8 km. The comparisons show that a lateral attenuation term is justified for best-practice models, resulting in a better agreement with measurements. However, sonAIR yields better results than the two other models, with deviations on the order of only ±1 dB at all measurement locations. A further advantage of a physically based modeling approach, as used in sonAIR, is its ability to account for varying conditions affecting lateral attenuation, like systematic differences in the temperature stratification between day and night or ground cover other than grassland.

Comparative assessment of measured and modelled aircraft noise around Amsterdam Airport Schiphol

The impressive growth of the aviation industry and the number of flights entail several environmental repercussions, such as increased aircraft noise emissions. With the worrying number of complaints from the communities around airports comes also the distrust in numerical models used for aircraft noise prediction. In this study, we compare the ‘Dutch aircraft noise model’ predictions to measured values from the NOise MOnitoring System (NOMOS) around Amsterdam Airport Schiphol between 2012 and 2018. While the model underestimates aircraft noise in 2012, the model prediction improved throughout the years. We observe a decreasing trend of measured aircraft-related L d e n values of 0.6 dB(A)/year (a total of 3.6 dB(A) over the investigation period), although the total number of flight movements increased during the observation time. We propose that a change in fleet mix, as well as the implementation of Noise Abatement Procedures at Schiphol Airport, fuelled this trend.

Guidelines for the LTO Noise Assessment of Future Civil Supersonic Aircraft in Conceptual Design

One of the most critical regulatory issues related to supersonic flight arises from limitations imposed by community noise acceptability. The most efficient way to ensure that future supersonic aircraft will meet low-noise requirements is the verification of noise emissions from the early stages of the design process. Therefore, this paper suggests guidelines for the Landing and Take-Off (LTO) noise assessment of future civil supersonic aircraft in conceptual design. The supersonic aircraft noise model is based on the semi-empirical equations employed in the early versions of the Aircraft NOise Prediction Program (ANOPP) developed by NASA, whereas sound attenuation due to atmospheric absorption has been considered in accordance with SAE ARP 866 B. The simulation of the trajectory leads to the prediction of the aircraft noise level on ground in terms of several acoustic metrics (LAmax, SEL, PNLTM and EPNL). Therefore, a dedicated validation has been performed, selecting the only available supersonic aircraft of the Aircraft Noise and Performance database (ANP), that is, the Concorde, through the matching with Noise Power Distance (NPD) curves for LAmax and SEL, obtaining a maximum prediction error of ±2.19%. At least, an application to departure and approach procedures is reported to verify the first noise estimations with current noise requirements defined by ICAO at the three certification measurement points (sideline, flyover, approach) and to draw preliminary considerations for future low-noise supersonic aircraft design.

Aircraft Noise Modeling of Departure Flights based on Flight Track Data and Actual Aircraft Performance Parameters

Abstract The improvement of existing and the development of new operational noise abatement departure procedures (NADP) requires precise knowledge of the current aircraft noise situation in the vicinity of an airport. While the current noise situation is recorded using aircraft noise measurements, the estimation of future aircraft noise in the vicinity of airports must be calculated using suitable modeling methods (e. g. ECAC Doc 29). So far, the methods for estimating aircraft noise have been based on generic departure profiles and assumptions about flight operations procedures that do not match the real departure profiles, flight performance statuses and operational flight operations procedures sufficiently. In this article a method is presented that enables the calculation of aircraft noise contours of real departures using the aircraft noise modeling software Aviation Environmental Design Tool (AEDT). The exact calculation of aircraft noise contours from departures is based on a data set of flight history data (radar data), including the detailed estimation of aircraft performance parameters (including aircraft mass and engine thrust) and flight operations procedures (cutback and acceleration heights, flap schedule) along the departure trajectory. Then the data set is implemented in the modeling software and the calculated noise metrics (LA,MAX) are validated with real aircraft noise measurements of the corresponding flights.

Aircraft noise immission modeling

This contribution to the CEAS special edition Aircraft Noise Generation and Assessment focuses on the simulation of the aircraft noise immission, i.e., the aircraft noise received on the ground. This process includes two steps, the description of the sound emission by the aircraft and the modeling of the sound propagation through the atmosphere. An overview is provided on how aircraft noise immission can be described and assessed by noise descriptors. These quantities can be derived from measurable and computable quantities like maximum sound levels, time-integrated sound levels and the number of aircraft movements. Moreover, a generation of novel noise indices which relate human reactions to noise is presented. Fundamentals of aircraft noise modeling are explained. First, this includes a classification of aircraft noise models into best practice and scientific models and their applicability to the noise mitigation measures described by ICAO’s Balanced Approach to Aircraft Noise Management. Furthermore, the overall workflow of a noise modeling task is explained as well the special role of noise model databases and the simulation of aircraft flight paths. The most common methods used to describe the sound propagation process through the atmosphere are introduced. This covers the modeling of the fundamental propagation effects which are used by all noise model types as well as a description of propagation effects which are of importance only for special modeling tasks and which normally require sophisticated physical approaches. The fundamental difference between best practice and scientific aircraft noise models—i.e., the source modeling—is described in detail thereafter. Best practice models are based on a simple source description. Moreover, a common approach is to combine emission and propagation using pre-calculated noise–power–distance tables. In contrast, scientific models are of multi-source type, i.e., they differentiate between particular noise-generating mechanisms—at least between engine noise and aerodynamic noise. This model type always requires a time step-based flightpath description, whereas the best practice models usually are based on a flightpath description by longer segments. Finally, the selected application examples are presented for both model categories. This covers the range from noise zoning over what-if studies for noise mitigation measures or definition of noise abatement flight procedures up to the modeling of noise reduction measures at the source. Finally, the application of scientific models in the aircraft design phase is explained.

Acoustic validation of military aircraft noise models

The National Environmental Policy Act (NEPA) of 1970 established the requirement to assess noise impacts from aircraft operations on the community surrounding military bases. A process for measuring and modeling aircraft noise sources and their propagation to ground locations was developed in response. The NOISEMAP suite of software programs produces noise footprints of yearly average impacts due to all flights that occur to and from an airbase. Through NOISEMAP’s decades of evolution, it retains the same fundamental measurement/modeling architecture and remains the approved model for environmental impact studies for aircraft within the U.S. Department of Defense (DoD). However, new advanced source and propagation models exist, which result in lower uncertainties and the calculation of additional useful noise impact metrics. No clear path exists to allow the use of these models for DoD environmental impact studies. This work presents a scientific validation experiment for aircraft overflight source/propagation models, focusing on suitability for use in a NEPA environmental impact study. The experiment relies on high-fidelity data collected during controlled overflight acoustic measurements of real aircraft and provides a quantitative benchmark for the evaluation of future models.

Full-spectrum near-field acoustical holography for fighter jet noise imaging

The development of acoustic imaging technologies over the previous decade has proven useful for increasing our understanding of the noise generation mechanisms inside the turbulent flows of full-scale tactical aircraft engines. In particular, advancements in near-field acoustical holography have allowed for jet noise source imaging from measurements made on tied-down aircraft over hard reflecting ground surfaces. These images have been limited in bandwidth due to the spatial resolution and extent of the holography arrays. However, improved aperture extension methods have allowed for representation of the lowest frequencies, and a new tool has been developed to produce accurate sound field images at above-Nyquist frequencies for broadband sources. These two technologies are implemented together to extend the imaging of fighter jet noise near-field toward the full spectrum required for an aircraft noise model.The development of acoustic imaging technologies over the previous decade has proven useful for increasing our understanding of the noise generation mechanisms inside the turbulent flows of full-scale tactical aircraft engines. In particular, advancements in near-field acoustical holography have allowed for jet noise source imaging from measurements made on tied-down aircraft over hard reflecting ground surfaces. These images have been limited in bandwidth due to the spatial resolution and extent of the holography arrays. However, improved aperture extension methods have allowed for representation of the lowest frequencies, and a new tool has been developed to produce accurate sound field images at above-Nyquist frequencies for broadband sources. These two technologies are implemented together to extend the imaging of fighter jet noise near-field toward the full spectrum required for an aircraft noise model.

Modeling of Aircraft Takeoff Weight Using Gaussian Processes

The takeoff weight of an aircraft is an important aspect of aircraft performance. However, the takeoff weight of a particular flight is generally not available to entities outside of the operating airline. The preceding observations motivate the development of accurate takeoff weight estimates that can be used for fuel-burn estimation or trajectory prediction. This paper proposes a statistical approach based on Gaussian process regression to determine both a mean estimate of the takeoff weight and the associated prediction interval, using observed data from the takeoff ground roll. The model development and validation are conducted using flight data recorder archives, which also provide ground-truth data. The models are found to have a mean absolute error in takeoff weight of 3.6%, averaged across nine different aircraft types, resulting in a nearly 35% smaller error than the models in the Aircraft Noise and Performance database. Finally, the developed models are used to predict aircraft fuel flow rate during climb out and approach. For the majority of the aircraft types studied, the statistical models of takeoff weight estimation are shown to result in a similar or better fuel flow rate predictive performance as compared to the Aircraft Noise and Performance models.

Meteorological reanalysis data inputs for improved aircraft noise modeling

In order to improve the prediction capabilities of aircraft noise modeling tools, recent work has focused on including measurements of the vertical structure of the inhomogeneous propagation environment. Meteorological reanalysis incorporates quality-controlled measurements from many sources into atmospheric models, which produce 4-D data fields describing the state of the atmosphere. In this work, reanalysis products are considered for use in the calculation of aircraft noise propagation from en-route and lower altitudes to the ground. Atmospheric profiles are extracted from the NCDC/UCAR Climate Forecast System Reanalysis (CFSR) and input to an acoustic raytracing model to demonstrate effects of realistic inhomogeneous atmospheric conditions throughout the propagation path. Results will be discussed, as well as practical and methodological considerations for data integration. The techniques demonstrated for this data set should also be applicable for other similar data sets, and thus may be useful in the future development of the Federal Aviation Administration's (FAA) Aviation Environmental Design Tool (AEDT). [Work supported by the FAA. The opinions, findings, conclusions, and recommendations expressed in this material are those of the authors and do not necessarily reflect the views of ASCENT FAA Center of Excellence sponsor organizations.]

Kenneth Plotkin——Military noise and sonic boom

As a young researcher at the Air Force Research Laboratory, I was blessed with the good fortune of working with Ken on a variety of military sonic boom and aircraft noise projects. His mentorship on sonic boom theory required patience on his part but resulted in a successful collaboration, which included an improved PCBoom model and focused sonic boom measurements. From this work, we demonstrated how to make sonic booms louder unlike his later efforts to help minimize future aircraft's sonic booms. Ken also led major upgrades to the military’s aircraft noise model, NoiseMap. His work resulted in the development of the simulation noise model, NMSim and its noise animations. Through Ken’s efforts, we now have tools to better explain sonic boom and aircraft noise. As my mentor, I hope to share some highlights of working with Ken.

Quantifying uncertainties in predicting aircraft noise in real-world situations

A relatively new project in the ASCENT Center of Excellence at Penn State and Purdue is focused on validating aircraft noise models and quantifying uncertainties of both model prediction and measurement. Multiple data sets are being identified for the validation efforts, and these will be described. This presentation will particularly focus on the BANOERAC and Vancouver Airport Authority data sets. Meteorological influences are very important in assessing the uncertainties on received sound levels from aircraft, so having weather data in conjunction with sound level measurements is essential. An ultimate outcome of the project will be a better understanding of the needs for acoustic and meteorological data to validate modern aircraft noise propagation tools such as the FAA's Aviation Environmental Design Tool (AEDT) and the parabolic equation (PE) algorithm. [Work supported by the FAA. The opinions, findings, conclusions, and recommendations expressed in this material are those of the authors and do not n...

Study of lateral attenuation for aircraft noise modeling based on field measurements near the airport

It is essential to appropriately evaluate effects of lateral attenuation in predicting aircraft noise at the side of flight path near the airport. About fifteen years ago, we examined the validity of existing equations of lateral attenuation, but noise characteristics of aircraft and engines have changed very much. Especially, in case of horizontal sound propagation over ground such as aircraft rolling on the runway, it is necessary to take into account that meteorological conditions may strongly affect lateral attenuation. Thus, we carried out field measurements of aircraft noise repeatedly on the side of runway at several airports including Narita Airport and examined the actual situation of lateral attenuation. As a result, it was found that lateral attenuation greatly changes dependent on meteorological conditions and that calculations from existing equations of lateral attenuation did not match measurements of lateral attenuation. Additionally, considering actual situation of land use around the airp...

Lou Sutherland—The man and his work

Lou Sutherland is one of the longest serving members of the international acoustics community and one of the most prolific. In a career lasting over 60 years, his main areas of research have involved studies of human and structural response to noise, sonic boom and blast, but his contributions to the fields of acoustics and vibration have been much more diverse and have included topics such as atmospheric absorption, aircraft noise measurement and modeling, low-frequency noise, and acoustic testing. He has been active in standards organizations and as a result of his services has been elected as a Fellow in several professional societies. As a consultant, Lou had the ability to break down complex problems into simple components that could be understood and solved, often using limited available data and simple theoretical models. Lou is still active as a consultant and continues to influence people with his ideas. As a long-term colleague, the author will examine some of his major contributions and share s...

Uncertainty quantification of an Aviation Environmental Toolsuite

This paper describes uncertainty quantification (UQ) of a complex system computational tool that supports policy-making for aviation environmental impact. The paper presents the methods needed to create a tool that is “UQ-enabled” with a particular focus on how to manage the complexity of long run times and massive input/output datasets. These methods include a process to quantify parameter uncertainties via data, documentation and expert opinion, creating certified surrogate models to accelerate run-times while maintaining confidence in results, and executing a range of mathematical UQ techniques such as uncertainty propagation and global sensitivity analysis. The results and discussion address aircraft performance, aircraft noise, and aircraft emissions modeling.

Multi-disciplinary simulation of propeller-turboprop aircraft flight

AbstractThis contribution presents a novel simulation for a fixed-wing aircraft powered by gas turbine engines and advanced propellers (turboprops). The work is part of a large framework for the simulation of aircraft flight through a multi-disciplinary approach. Novel numerical methods are presented for flight mechanics, turboprop engine simulation (in direct and inverse mode), and propeller dynamics. We present in detail the integration of the propeller with the airframe, aircraft and tonal noise model. At the basic level, we address a shortfall in multi-disciplinary integration in turboprop-powered aircraft, including economical operations and environmental emissions (exhausts and noise). The models introduced are based on first principles, supplied with semi-empirical correlations, if required. Validation strategies are presented for component-level analysis and system integration. Results are presented for aerodynamics, specific air range, optimal cruise conditions, payload-range performance, and propeller noise. Selected results are shown for the ATR 72-500, powered by PW127M turboprop engines and F568-1 propellers.