Capabilities of IESTA-CARMEN to predict aircraft noise

2017

In line with the goal of cleaner and quieter aircraft, this paper investigates propeller acoustics aiming to improve turboprops noise emissions, as they represent the best choice for short and medium range flights in terms of fuel efficiency. CFD is used to analyse the propeller-airframe interaction physics, and assess propeller installation effects, for a full scale twinengined aircraft. The employed propellers represent advanced designs currently used in modern aircraft and the cases of co-rotating and counter-rotating top-in layout are considered. The URANS approach is used on grids of up to 195 M points aiming to directly extract from CFD the noise tonal content. Numerical results are first validated against modelscaled experimental data. A comparison between results of the full aircraft and a propeller in isolation is also carried out. Full aircraft predictions show significant differences in the external acoustics between port and starboard sides for the co-rotating case, with...

Journal of Sound and Vibration, 2001

Acoustical properties of aircraft noise were investigated by means of temporal and spatial factors in sound "elds based on the model of auditory}brain system (see reference ). The model consists of the autocorrelation and crosscorrelation mechanisms for sound signals arriving at two ears and the specialization of human cerebral hemisphere. There are four temporal factors extracted from the autocorrelation function (ACF): (1) sound energy (2) e!ective duration of ACF, ; (3) delay time of the "rst peak, ; and (4) its amplitude . From the interaural crosscorrelation function (IACF), three spatial factors are extracted as (1) magnitude of the interaural crosscorrelation IACC (2) interaural delay time at IACC, '!! , and (3) width of the maximum peak of the IACF, = '!! . It is found that the acoustical properties are well represented by the factors extracted from the ACF and the IACF.

Acoustics, 2020

The present work deals with the modeling of the aerodynamic sound generated by the propellers of small-size drones, taking into account the effects of horizontal forward flight with negative pitch and of installation on supporting struts. Analytical aeroacoustic formulations are used, dedicated to the loading noise. The fluctuating lift forces on the blades are expanded as circular distributions of acoustic dipoles, the radiated field of which is calculated by using the free-space Green’s function. This provides descriptions of the sound field, valid in the entire space. The stationary mean-flow distortions responsible for the lift fluctuations and at the origin of the sound are estimated from existing numerical flow simulations and from ad hoc models. Installation and forward-flight effects are found to generate much more sound than the steady loading on the blades associated with thrust. Therefore, the models are believed reliable fast-running tools that could be used for prelimin...

Within the EU-FP7-project COSMA combined flight path and acoustical measurements of aircrafts were performed at Munich Airport in order to relate the sound propagation of aircrafts to their position in space. Applying time varying back-propagation radiant from the microphone position on the ground to the aircraft position in space this procedure allows to isolate spectral components of the sounds without atmospheric damping effects. Using a new synthesis methods as developed in COSMA (ANCS: Airport Noise Climate Synthesizer ) the separated components can be varied experimentally e.g., in level and/or spectral shape to test the psychometric effects of these manipulations in the laboratory. In addition to these source related changes different environmental variables like atmospheric conditions and/or flight path modifications can be imposed on the sounds, too, which may help to e.g., optimize the quality of aircraft sounds. The paper will demonstrate the measurement procedure and subsequent processing of the sounds. Finally a 3D-auralization method will be presented which has been used in COSMA to test the sound quality of synthetic versus natural aircraft sounds.

Noise Control Engineering Journal, 2012

Aircraft noise has adverse impacts on passengers, airport staff and people living near airports, it thus limits the capacity of regional and international airports throughout the world. Reducing perceived noise of aircraft involves reduction of noise at source, along the propagation path and at the receiver.

International Journal of Aeroacoustics, 2014

the topic "Atmospheric and Ground Effects on Aircraft Noise" and it was organized by Nico van Oosten (Anotec Consulting) and Emilio Campos (Association of Aeronautical Engineers of Spain), the latter being also the chairman of the scientific committee. The relevance of the topic arises from the need to get an accurate evaluation of the noise impact around airports, and to that end since the effects of atmosphere, ground, and topography on the propagation of sound can become important, they must be taken into account in the calculation of the aircraft noise perceived on the ground. 57 people attended the workshop, from 20 countries (EU states, Norway, Ukraine, Russia, USA, and Japan), and 20 papers were presented, of which 3 were invited lectures and the others classified in 5 sessions: Meteorological Effects, Effects of Turbulence, Modelling of Atmospheric and Ground Effects on Aircraft Noise, Long Range Sound Propagation Studies, Assessment of Atmospheric and Ground Effects in Methodologies Related to Airport Noise. In recent years long range sound propagation prediction has been carried out by using computational tools based either on the parabolic equation or on fundamental approaches like the linearized Euler equations (e.g. Finite Differences Time Domain-FDTD-models) among others. One of the main objectives of the workshop was to assess the efficient application to aircraft noise prediction of those tools, including the ground and atmospheric effects on sound. Besides, since geometrical acoustic models are still in use, either alone or in combination with the former approaches, it was also deemed interesting to investigate the capabilities of these models to deal with those effects. Experimental studies on meteorology effects on sound propagation were also encouraged. Most of the suggested topics were dealt with in the contributed papers, some of which have been selected to appear in this issue as shown below. In A fast atmospheric sound propagation model for aircraft noise prediction, M. Tuinstra presents an analytical approach, based on approximating the wavefront orientation perpendicular to the ray path, from which an adapted form of Snell's law for a ray is derived, as well as discretizing the atmosphere in layers of linearly varying sound speed and wind velocity. Other ray-based approach is that of H. Brouwer in his paper A ray acoustics model for the propagation of aircraft noise through the atmosphere which shows the development of a ray-tracing tool for a stratified atmosphere, derived from the linearized Euler equations (LEE), including an analysis under various atmospheric conditions. Time domain methods are dealt with in two contributions, one of them by T.Van Renterghem, entitled Efficient outdoor sound aeroacoustics volume 13 • number 5 & 6 • 2014-pages i-iv i

25th AIAA/CEAS Aeroacoustics Conference

The Aircraft Noise Working Group (ANSWr) was established by DLR, ONERA, and NASA to compare simulation tools, establish guidelines for noise prediction, and to assess uncertainties associated with the simulation. To accomplish these goals, a benchmark problem was initiated by the group. The setup is documented and initial results for the reference aircraft are discussed. The reference aircraft is a conventional tube-andwing configuration with the engines installed under the wings. The aircraft noise simulations are performed for departure and approach conditions, and the results obtained with three different system noise prediction tools are compared. At the aircraft level, the overall agreement is good between the three predictions. Peak noise levels agree within 3-4 dB. Fan and jet component predictions are generally very similar although there can be differences of up to 7 dB in some fan tone levels. The prediction of airframe components shows the most disagreement between the three methods with some differences of 6 dB for the major components and greater differences at high frequencies. There can also be differences in the frequency of the peak level and in the rank order of the airframe components. At the total airframe noise level, the differences are reduced to no more than 3-4 dB. While there is general agreement in shape characteristics of predicted ground noise isocontours, the differences between the three methods can result in more significant disagreement in the sizes of the isocontours.

25th AIAA/CEAS Aeroacoustics Conference, 2019

Aircraft noise is an increasingly important issue that causes annoyance and complaints for the communities living in the vicinity of airports. The conventional sound metrics (such as the A-weighted sound pressure level) typically used for assessing the impact of aircraft noise often fail to conveniently represent the actual annoyance experienced. More sophisticated sound quality metrics (such as loudness, tonality and sharpness) can be used to determine the psychoacoustic annoyance perceived by the human ear. In this paper, an Airbus A320 landing flyover under operational conditions recorded with a microphone array is analyzed. The application of functional beamforming to the acoustic data allows for the separation of the emissions of different noise sources on board of the aircraft. For this case, the nose landing gear (NLG) and the turbofan engines were selected, due to their expected dominance during approach. It was found that, despite being more quiet than the turbofan engines, the NLG system emits a strong tonal sound that makes it overall more annoying than the noise of the engines. Airframe noise prediction models (Fink's and Guo's methods) do not consider this tone and considerably underpredict the noise levels and the annoyance of the NLG. Thus, it is highly recommended to employ these sound quality metrics to study aircraft noise and to evaluate the potential improvement in annoyance of future low-noise aircraft concepts, rather than just a difference in the sound pressure level in decibels.

2019

This paper introduces the activities performed at University of Naples Federico II within the ADORNO research project. ADORNO project, "Aircraft Design and NOISE Rating for regional aircraft" is a research project financed by European Commission under the Horizon 2020 Program Clean Sky 2, focused on the development of aircraft models for a regional aircraft engine platform. The main objective is to evaluate the benefits of Clean Sky 2 developed technologies at aircraft system level, with respect to gaseous and noise emissions. One of the enablers is the development of an efficient noise prediction tool and its integration into an existent aircraft design and analysis chain. The developed tool can model the "near field" noise sources and with a propagation model estimate noise level in the space. The paper presents an application of noise estimation (Effective Perceived Noise Level) on the certification points (flyover, sideline and approach) of a regional turbofa...

2015

Noise assessment around airports is hampered due to the observed large variability in noise levels for fly-overs of the same aircraft type, which is not considered by the current models. This paper assumes that the noise variability is due to variations in the aircraft emitted noise, neglecting the effect of the variable atmosphere, as previous work showed that its contribution is maximally 2 dB. In order to quantify and investigate the variability of noise levels during aircraft fly-overs, 115 measurements of noise of landing aircraft were taken using a 32 microphone array. The noise levels from Boeing 737 fly-overs were analyzed and the noise level variability was determined to be approximately 16 dB. After determining the engine settings from the spectrograms, it was found that variations on the engine settings explain over 55% of the observed total noise variation. In addition, by performing beamforming on the acoustic data, it was confirmed that airframe noise (from the landing...