Aircraft Noise Emissions Research Articles

Estimation of the Fan Rotational Speed Using Flyover Audio Recordings

Aircraft noise emissions affect societies around the world by impacting the population’s health and land use planning. This calls for simulation tools able to predict these types of noise emissions with high accuracy. A crucial aircraft parameter to achieve satisfying precision is the rotating frequency of the low-pressure shaft of the turbofan engine, called N1. N1 determines the engine’s power use and is here estimated acoustically from ground-based microphones. A new method for dynamic N1 estimation is presented, which is more robust as compared to earlier approaches. It makes use of different aircraft sound characteristics and combines two methods. The first method tracks multiple fan tone harmonics over time within a de-Dopplerized sound pressure spectrogram. This frequency-tracking task is solved by dynamic programming to find the global optimum. The second method relates to buzz-saw noise, and is thus applied to departures only. The buzz-saw fundamental frequency is estimated in the cepstral domain. Both submethods are separately validated and assessed with concurrent sound pressure measurements and flight deck recording data of N1. The new robust N1 estimation method will be applied in noise measurement campaigns with the goal of improving current aircraft noise emission models.

Acoustic source characterization of simulated subsonic jet noise using spherical harmonics

As subsonic jets remain one of the major contributions to aircraft noise emissions, near-field flow simulations should be included in aircraft design at an early stage using quantitatively predicted sound pressure levels and the time-domain signal properties of the noise data. In this regard, the interface from the near-field data to the far-field radiation—under consideration of acoustic reflections from objects such as fuselage and wings—remains as bottleneck. This study presents the computation of a spherical equivalent source model of jet noise with minimal complexity by means of spherical harmonic (SH) coefficients. Using spherical Hankel extrapolation of sound pressure data from virtual, concentrical microphone arrays, the results of the determination for the radius, in which all acoustic sources of a flow field are confined, indicate the source radius around the end of the potential core to be equivalent to five times the nozzle diameter. The result of the SH transform shows the dominant energy contribution to be related to nine elementary sources. The resulting equivalent source model of jet noise provides a convenient format for further use in large-scale computational fluid dynamics simulations.

Microphone location investigation for standard aircraft ground run-up noise measurements

The correct placement (height, orientation, and mounting techniques) for microphones used in standard data collection practices for aircraft environmental noise models is a topic of debate. Previous studies have demonstrated and quantified the dependence of spectral data recorded as a function of microphone placement variations and relative source origin. In this work, an in-depth investigation of microphone mounting effects is performed with an emphasis on (1) microphone height and (2) ground-mounting configuration for the purpose of quantifying ground run-up aircraft noise emissions for environmental noise model generation. Data for this investigation were collected on the T-7A Red Hawk in both standard (see ANSI S12.75-2012) and off-standard configurations for comparison.

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.

Uncertainty Quantification for Aircraft Noise Emission Simulation: Methods and Limitations

Implementing measures for the reduction of aircraft noise impact, such as optimization of flight paths and aircraft, requires sophisticated simulation capabilities. These tools have to incorporate simulation of aircraft noise generation at the source (i.e., emission) and account for prevailing sound propagation effects to ultimately predict noise levels as received on the ground. Obviously, understanding the associated uncertainties is crucial when aiming at a reliable and meaningful assessment. It also becomes essential when comparing different technologies, mixing experimental and numerical data, or using simulation methods of different fidelity (e.g., semi-empirical and first-order methods). This research focuses on quantifying uncertainties in the first step in aircraft noise simulation (i.e., the prediction of the emission situation). The quantified uncertainties reflect imperfections of models for different aircraft noise sources and variability of model input parameters at different operating conditions. A general framework is presented, which also accounts for limited knowledge of the underlying data distributions, and quantitative comparisons of different uncertainty methods are provided. In particular, the first-order second-moment analysis is compared to higher-order polynomial chaos methods, and the advantages and disadvantages of the different methods are discussed.

Microphone placement investigation for standard aircraft ground run-up noise measurements

The correct placement (height, orientation, and mounting techniques) for microphones used in standard data collection practices for aircraft environmental noise models is a topic of frequent debate. Previous studies have demonstrated and quantified the dependence of spectral data recorded as a function of microphone placement variations and relative source origin. In this work, an in-depth investigation of microphone mounting effects is performed with an emphasis on (1) microphone height and (2) ground-mounting configuration for the purpose of quantifying ground run-up aircraft noise emissions for environmental noise model generation. Data for this investigation were collected on the T-7A Red Hawk in both standard (see ANSI S12.75-2012) and off-standard configurations for comparison.

Effects of the reduction of aircraft noise emission due to the travel restriction during the COVID-19 pandemic at residential areas around Tan Son Nhat Airport

The travel restrictions caused by the epidemic outbreak in early 2020 worldwide have caused many changes in all aspects of life, especially in the acoustic environment. This study examines the impact of this environmental change at Tan Son Nhat International Airport (TSN), the largest airport in Vietnam, by comparing the situations before and after the airport stopped operating all international flights in March 2020. The after-the-change survey was conducted in 2 phases, June and September 2020, three months and six months after the stop decision. The number of flights observed in August 2019 was 728; this number is 413 and 299 for the two surveys in 2020. The range of noise levels estimated for 12 sites around TSN decreased from 63-81 dB in 2019 to 32-67 dB in June 2020 and 33-69 dB in September 2020. At the same aircraft noise level, the percentage of highly annoyed (% HA) and the percentage of insomnia (%ISM) in the 2020 survey are higher than those in the 2019 survey. The comparison results of reaction to noise before and after the TSN's noise change indicated an increase in negative responses to noise might happen in the increased noise and reduced noise situation.

Assessment of Aircraft Noise Emissions at International Eskisehir Hasan Polatkan Airport with Multiple Approach Model

Aircraft noise emissions are a problem that negatively affects human health, directly or indirectly. For this reason, examining and managing the noise effects caused by aircrafts at the airports is important for the sustainable development of aviation. In the present study, a noise management model based on the multiapproach method, including some actions related to aircraft noise, has been created. The model was applied to the International Eskisehir Hasan Polatkan Airport (LTBY). Within the scope of the model, in the first stage, in 365 days, day, evening and night noise levels around the airport were simulated using IMMI software under the European noise directive and European Civil Aviation Conference (ECAC) doc 29-interim was also used to measure aircraft noise. In the second stage, the noise generated by the Cessna 172-S aircraft under different operating conditions experimentally measured was carried out. After the model had been applied to LTBY, improvement opportunities for aircraft noise were evaluated. It is thought that the study and its results will help other civil airports on the issue of noise problem at airports.

Aircraft noise level calculation during take-off

A mathematical model with 4 degree of freedom created in Matlab for aircraft departure trajectory is described in this article. As a reference aircraft a midsize commercial passenger aircraft similar to an Airbus A320 has been chosen. The aircraft is represented by the rigid body and the parameters of model are collected from Airbus and the simulated departure trajectory at the Munich airport is based on a Standard Instrumental Departure. A semi-empirical model of Stone for predicting the jet noise has been used. The proposed model is validated against 10 real flights obtained from aircraft noise and flight track monitoring system at Munich airport. The computed error between the real data and modelling is reported on. Obtained results are presented numerical and graphically. The observed effects of flight operational parameters affecting the aircraft noise emission level during take-off represent subjects of discussions in the paper.

The 1952 Rome Convention on Surface Damage and Its Application in the Case of Aircraft Noise Emission: The Example of Belgium

Although the 1952 Rome Convention on Surface Damage does not account with as many ratifications as the 1999 Montreal Convention or its predecessors, it organizes what can be seen as an operators’ friendly liability regime. In a recent landmark ruling in a matter that was pending before the Belgian courts for nearly twenty years, the Court of Appeal of Brussels held that airlines could not be held liable for the prejudice allegedly caused by their aircraft’s noise emissions to the extent that these aircraft and their operations comply with the rules of air.

Study of the correction factors for aircraft noise façade measurements

Nowadays, society has the need for air transportation all around the world. The yearly increase in the number of passengers forces airports to operate to a maximum of their capacity. This leads to an augmentation of the fleet of each airline and consequently to an increase in aircraft noise emissions. Accordingly, procedures for measuring aircraft noise levels have been developed. There are international standards that specify how transport noise (aircraft, traffic and railroad) must be measured. ISO 1996-2 standard has an appendix called Annex B which specifies the reference position of the microphone to undertake the measurement, and simplified correction factors to use in case that the measurement must be located near a reflecting surface (3 dB) or directly over a reflecting surface (6 dB). A façade behaves like a reflecting surface and the correction factor to apply is relevant to the study of noise because with the reflections produced on the outside of a building, people nearby can be affected. Therefore, numerous studies verifying the correction factors of ISO 1996-2 Annex B have been performed on façades, particularly for traffic noise. Most of the findings from these studies demonstrate that features of the source-receiver geometry change the correction factor. However, this correction factor has not been tested yet for aircraft noise whose source-receiver geometry differs from that of traffic noise. This paper intends to test the correction factor for aircraft noise on façade. It also tries to determine which relationship can be found among the noise level at the reference position and features like the façade noise level, source-receiver geometry and flight type.

Aircraft Noise Emission Model Accounting for Aircraft Flight Parameters

Today’s aircraft noise calculation programs either use simple sound source descriptions with few input parameters or highly sophisticated models with input parameters, which are difficult to obtain. To fill the gap between these two approaches, an aircraft noise emission model based on regression of measured noise with aircraft flight parameters is presented. To find a reasonable compromise between the degree of detail and number of required flight parameters, an extensive data exploration was conducted. The most relevant parameters were incorporated in two multiple linear regression models, one for airframe and one for engine noise sources. An iterative method allowed fitting both regression models to aircraft flyover measurements. In total, aircraft noise emission models for 19 aircraft types were established, which underlines the general applicability of the modeling approach to turbofan-powered aircraft. Example comparisons between measurements and model predictions for two aircraft types revealed that the model accurately reproduces directivity and spectra for different flight configurations. In addition, it is suitable for the assessment and optimization of noise abatement procedures.

Noise Restriction Measures and the ‘Balanced Approach’: The Situation at Brussels-National Airport

This article provides an overview of the rules for adopting noise restriction measures at a specific airport. In the first part, after having emphasized the importance of regulating aircraft noise emissions, this article examines the relevant international and European legal framework. In the second part, it focuses on a decision of the Brussels-Capital region concerning noise at Brussels-National airport. It will be suggested that this decision does not respect the legal framework dealt with in the first part. Finally, and in conclusion, it transpires that the solution is to be found on a political level The content of this article has been based on information correct at the date of 9 May 2017.

Vienna international airport noise abatement

Purpose: On the topic of sustainable aviation a study was carried out to measure the difference between the actual change in air traffic noise and the airport’s residents’ perception of the noise change at Vienna International Airport. Therefore, a questionnaire was developed in cooperation with the airport and an online survey was conducted.Design/methodology/approach: For the survey of the opinion of the affected population of the surrounding communities, a web based online questionnaire is created and distributed via various channels including e-mail, and online forums. After the basic structure of the questionnaire had been defined, the questions were developed in cooperation with employees form the environmental department of VIE, who had a sustainable influence on the questions’ order and formulation. As the survey was supposed to be answered by residents around VIE.Findings: Results of the online study show that only parts of the participants are affected by air traffic noise at VIE. Even less experienced a significant change over the last five years. About one third of the participants stated that they are affected by air traffic noise in one way or another. The majority of these people live in Lower Austria, the federal state in which the airport is located. The participants obviously judge air traffic noise during day time more importantly than air traffic noise at night.Research limitations/implications: Due to the low number of returns, no statistically relevant conclusions can be drawn, the results of the survey can be used to make some general statements.Originality/value: Economic growth and deregulation lead to growing aircraft operations. Vienna International Airport with its approximately 260,000 flight movements per year is the biggest airport in Austria and a major hub in Europe. The combination of constantly growing air transport and the resulting noise exposure, as well as the steadily increasing sensitization of the population, bring the issue of aircraft noise emission into the increased interest of the stakeholder of an airport. The study compares the extent of the subjective perceived and the actual noise emissions’ change over the last years.

Boeing Measures Reduced Aircraft Noise Emissions with NI PXI and LabVIEW

Boeing Measures Reduced Aircraft Noise Emissions with NI PXI and LabVIEW

Reduction of commercial aircraft noise emission around airports. A new environmental challenge

Abstract Noise abatement procedures (NAPs) are considered as a necessary measure for a balanced approach of noise control around airports. Their correct implementation depends upon many factors, which vary in operation and influence the efficiency of the NAPs. Any system, which defines the correct features of the NAPs for particular aircraft in specific conditions, would be useful for noise control. Thus, implementation of noise level monitoring systems, currently used around airports, gives a noise map in residential areas but cannot identify source frequencies and their impact on the environment. Consequently, this paper has been produced particularly to characterize the frequential aspect of aircraft noise emission. Its main objective is the analysis of the dominant frequencies emitted during approaches to the Lyon Saint-Exupéry International Airport (France) having a negative impact on the population living around this airport. Thus, the results obtained make it possible to show, through an empirical model of aircraft noise, the effectiveness of this experimental work.

A model based monitoring system for aircraft noise

A new approach for an airport noise monitoring system is presented that comprises not only a number of measuring stations, but also a dedicated sound propagation model and an aircraft noise emission model. This approach enables estimation of noise levels in the whole area around the airport and not only at the location of the measuring stations. An additional advantage is that the locations of the measuring stations can be chosen more freely. Traditionally the measuring stations must be located near residential areas where the influence of other noise sources (such as cars or wind) cannot be eliminated. Better locations can be found that yield more reliable data and therefore more reliable noise levels. To update the sound propagation model frequently, the measuring stations not only measure noise levels, but also other parameters, like temperature and wind profile. The sound emission of the aircraft is derived from a directional aircraft noise emission model. A tool was developed to visualize the power of combining data and models in this model-based monitoring system. The use of models opens possibilities for interesting applications such as i) short term noise forecasts, ii) scenario studies with various aircraft distributions and iii) enforcement of noise limits.

Assessment Of Noise Impacts At Airports

Airport operation is a major source of community concerns due to aircraft noise emissions particularly in locations close to airports and aircraft flight tracks. The effects of aircraft noise on humans can cause hearing damage for people working at airports and speech and sleep interference which can develop into stress for nearby communities. As such, it becomes essential when locating and designing to expand airports to optimize flight paths in a way to reduce noise exposure to nearby communities. For this purpose, it is required to assess changes in noise levels resulting from new runway configurations, evaluate increased aircraft operation demand, new fleet mix, revised routings and airspace structures, alternative flight profiles, and modifications to other operational procedures. This paper presents a noise impact assessment for the proposed expansion at the Beirut International Airport, Lebanon. Field noise measurements were collected at sensitive noise receptors along selected locations around the airport and the corresponding airport traffic flow was characterized. A mathematical model was then applied to simulate noise levels as a function of the different airplane classes, operations, flight path, and landing characteristics. The model was also used to predict future noise levels, optimize airplane flight path, and assess mitigation measures to minimize potential aircraft noise impacts.

Wideband noise signatures from low-altitude military jet overflights

Public concern about the noise from low-altitude military jet overflights and its alleged effects on the health and annoyance of those overflown has resulted in some restrictions on flying activities at low level, even bans within some countries, being imposed. Much past research into aircraft noise emissions has been based on band-limited noise measurements. Full pressure signatures are required if all possible noise effects are to be fully understood. In 1995 a series of trials was completed in the UK under controlled conditions, and typical wideband noise signatures obtained for a variety of speeds and heights of a Tornado aircraft. Samples of these signatures are presented and the various pertinent characteristics highlighted. The question as to whether these signatures should be considered impulsive is discussed.

Software system for quantitative, observer-based analyses of aircraft noise

The National Park Service’s Overflight Decision Support System (NODSS) now provides a functional capability for estimating airspace volumes above points and areas on the ground that should be avoided if aircraft are to remain unnoticed. Calculations of these volumes are sensitive to aircraft noise emissions, background noise levels at observers’ positions, terrain shielding, atmospheric absorption, and geometric spreading. NODSS provides a complete and consistent framework for performing acoustic detectability-based calculations as well as more conventional aircraft emission-based analyses, and produces results that can be displayed in easily understood graphic form. The initial use intended for NODSS is to perform engineering analyses of airspace restrictions associated with restoration of natural quiet in Grand Canyon National Park, pursuant to Public Law 100-91. [Effort supported in part by U.S. National Park Service.]