Pas de résumé / This work aims at developing a statistical prediction method for BroadBand Shock-Associated Noise (BBSAN), following recent work from NASA and Boeing. The approach is similar to studies performed for mixing noise models.First, a methodology has been developed to compute the mean turbulent _ow _eld using the Reynolds Averaged Navier-Stokes (RANS) equations. These equations are solved with elsA, a solver developed by ONERA. Most calculations have been performed on academic configurations. An extensive test campaign has been conducted on these configurations at Ecole Centrale de Lyon (ECL), so that calculations have been thoroughly compared to measurements. Mainly, two operating conditions have been tested. The first one is a jet at Mj = 1:15. This condition is typical of a civil engine in cruise. The second operating condition is a jet at Mj = 1:35, which rather concerns military engines.An acoustic model has been developed. It uses the RANS calculation as an input to compute Power Spectrum Densities (PSDs). The intermediate version of the model does not account for refraction effects: acoustic sources are propagated to the far-field using a free field Green's function. As will be seen, this gives good results on simple configurations.The model has been extended to account for refraction effects. This is achieved by computing a Green's function tailored to the problem. A ray tracing method coupled to an adjoint approach has been used to evaluate the Green's function. The computation of the Green's function has been validated for simple cases. The Green's function calculation has been coupled to the acoustic model. PSDs including refraction effects on dual-streamjets are presented.

<p>A few aspects of aircraft noise were evaluated. These were (i) methods of subjective evaluations, (ii) effects of equalization and (iii) the effects of cognitive aspects.</p><p>In the first paper, sorting algorithms were used instead of conventional paired comparison method in order to reduce the number of pairs in the evaluation of subjective judgments. The quick sorting algorithm method revealed more than 99% correlation coefficient with paired comparison method although the method used N*log(N) evaluations instead of N(N-1)/2.</p><p>In the second paper, equalization effects on perception were evaluated in two steps, first with stationary aircraft sounds and second with non-stationary aircraft sounds.</p><p>The first experiment examined the effects of stationary sound segments respect to three different angle positions of the aircrafts relative to the observer (78.7°, 90° & 101.3°), two different SNR conditions (sounds having original broadband plus tonal components versus control broadband sounds having no tonal components) and two different flight conditions (arrival and take-off). Subjects were asked to scale five perceptual attributes (loudness, annoyance, hardness, power and pitch) using Borg CR100 scale. The angle condition showed highly significant effects on annoyance and hardness. Maximal effects were found at an angle of 78.7°. The SNR revealed a significant impact on loudness, power and pitch.</p><p>The second experiment analyzed the effects of tonal components and the problem of appropriate equalization. The spectrum of the signals was modified in two steps (buzz-saw, isolated BPF tone). Further EPNL-equalization, A-, B-, C-, D- and spectral broadband equalizations were applied to the synthesized sounds. Annoyance, loudness, hardness and pitch in the isolated tone conditions showed significantly stronger effects than the buzz-conditions on the perceived judgments. The EPNL-equalization led to a lower degree of differentiation between the spectral conditions compared to B- and C-level equalization.</p><p>In the third paper, the effects of aircraft sounds on children’s cognitive performance were investigated. Impact of aircraft noise on children cognition was found significantly higher in reading comprehensions than in basic mathematics and problem solving tests. It seems children are very sensitive to the modifications in the aircraft noise but further studies are necessary to compliment such a finding.</p>

This diploma thesis deals with design of retractable landing gear for Rapid 600 aircraft. The main purpose of this thesis is to analyze different retraction options for front and main landing gear and resulting selection of suitable variants. The thesis is consequently concerned with design of selected options including proposal of automatic landing gear control system and specifying the features and characteristics of this system. In the thesis there is also included the analysis of critical flight conditions which could be detected by this system.

A few aspects of aircraft noise were evaluated. These were (i) methods of subjective evaluations, (ii) effects of equalization and (iii) the effects of cognitive aspects. In the first paper, sorting algorithms were used instead of conventional paired comparison method in order to reduce the number of pairs in the evaluation of subjective judgments. The quick sorting algorithm method revealed more than 99% correlation coefficient with paired comparison method although the method used N*log(N) evaluations instead of N(N-1)/2. In the second paper, equalization effects on perception were evaluated in two steps, first with stationary aircraft sounds and second with non-stationary aircraft sounds. The first experiment examined the effects of stationary sound segments respect to three different angle positions of the aircrafts relative to the observer (78.7°, 90° &amp; 101.3°), two different SNR conditions (sounds having original broadband plus tonal components versus control broadband sounds having no tonal components) and two different flight conditions (arrival and take-off). Subjects were asked to scale five perceptual attributes (loudness, annoyance, hardness, power and pitch) using Borg CR100 scale. The angle condition showed highly significant effects on annoyance and hardness. Maximal effects were found at an angle of 78.7°. The SNR revealed a significant impact on loudness, power and pitch. The second experiment analyzed the effects of tonal components and the problem of appropriate equalization. The spectrum of the signals was modified in two steps (buzz-saw, isolated BPF tone). Further EPNL-equalization, A-, B-, C-, D- and spectral broadband equalizations were applied to the synthesized sounds. Annoyance, loudness, hardness and pitch in the isolated tone conditions showed significantly stronger effects than the buzz-conditions on the perceived judgments. The EPNL-equalization led to a lower degree of differentiation between the spectral conditions compared to B- and C-level equalization. In the third paper, the effects of aircraft sounds on children’s cognitive performance were investigated. Impact of aircraft noise on children cognition was found significantly higher in reading comprehensions than in basic mathematics and problem solving tests. It seems children are very sensitive to the modifications in the aircraft noise but further studies are necessary to compliment such a finding.