Measurement of component's sound power emission on a PSA's diesel engine by means of 3D acoustic imaging techniques, and its applications

The identification and characterization of sound power radiated by engine components is an important challenge for car manufacturers such as PSA. This presentation will show the approach used, the results obtained and the analysis of those results during a study done with PSA to evaluate the contribution of each component on the total sound power radiated by an engine. In the first part of the study, a standard 2D acoustic imaging technique, based on combined holography and beamforming method, was used to evaluate the sound power radiated by faces of an engine and to identify the most radiating areas. The precision of this technique is however not sufficient to quantify the sound power radiated by components of the engine. This limitation is mainly due to the approximation of the engine face by a 2D plane. In the second part of this study, an innovating technique has been applied, using a 3D meshing of the engine and precise definition of each component on this meshing. Based on measurement done on an acoustic array successively positioned on four sides of the engine and a precise positioning of the array in regards to the meshing, it is possible to rebuild the sound power radiated by elements of the meshing and thus obtain the sound power spectrum radiated by each components of the engine for various configurations. Such experimental data have many interests for PSA: At first, it gives data concerning the overall acoustic power level of this engine. It gives information about the noisiest sources on each face of the engine. So, it gives orientation concerning the strategy of the noise reduction of the engine. It provides data to fix the different acoustic targets. By having the sound power level and spectrum of the mainly components, it is possible to build the targets to achieve by the suppliers on their benches. The comparison between the overall sound power level and the "sum-up" of the sound power level radiated by each component is a good way to be confident about the coherence between the overall target and the declined targets

On-board indirect measurements of the acoustic quality of railway track: state-of-the art and simulations

48th International Congress and Exposition on Noise Control Engineering (Inter-Noise 2019), MADRID, ESPAGNE, 16-/06/2019 - 19/06/2019Noise emission is a major concern for residents living along railway lines. For a large range of conventional speeds, railway noise is dominated by rolling noise. The contribution of the track to rolling noise is mainly driven by the level of rail roughness and the Track Decay Rate (TDR). The MEEQUAI project (on-board measurement of the acoustic quality of the infrastructure) aims to develop a system capable of measuring these characteristics using on-board instrumentation. A state-of-the-art on the subject shows that indirect measurement from vibro-acoustic sensors like axle-box accelerometers or microphones in the bogie area seems possible, but that a number of improvements could be made to the existing methods, especially in estimating the transfer functions between the e_ective roughness and the signals provided by the sensors. The idea is to combine modelling and measurements to optimize the estimation of the transfer functions and the location of sensors while taking into account the variability of circulated tracks. Numerical analyses of transfer functions based on axle/track vibro-acoustic models are performed. Based on the simulations results, several improvements are proposed, with a view to future tests in rolling conditions

Mesure embarquée de la qualité acoustique de l'infrastructure ferroviaire-Projet MEEQUAI

Journées Techniques Acoustique et Vibrations, STRASBOURG, FRANCE, 15-/05/2019 - 16/05/2019Pour les riverains des infrastructures ferroviaires, les émissions acoustiques constituent une préoccupation de premier plan. Parmi les sources incriminées, le bruit de roulement est prépondérant pour une large gamme de vitesses d'exploitation. Pour ce qui est de l'infrastructure, le niveau de bruit de roulement est principalement déterminé par deux paramètres : la rugosité des rails et le taux de décroissance des ondes vibratoires de la voie (TDR). Le projet MEEQUAI (MEsure Embarquée de la QUalité Acoustique de l'Infrastructure) vise à développer un système de mesure de la rugosité des rails et du taux de décroissance à l'aide de microphones et d'accéléromètres embarqués sur un train. Ce système a pour objectif principal d'améliorer la connaissance des données d'entrée pour la réalisation de cartographies acoustiques. Cependant, il ouvrira également de nouvelles opportunités pour le suivi dans le temps de la qualité acoustique des infrastructures ferroviaires ainsi que pour la maintenance des points singuliers tels que les joints de rail et les appareils de voie.Dans cette présentation, les mécanismes de génération du bruit de roulement sont présentés, notamment à travers le rôle de la rugosité et du taux de décroissance. Les principaux systèmes de mesure de ces paramètres sont passés en revue et les limites des méthodes indirectes examinées. Enfin, les résultats des premières études numériques et expérimentales réalisées dans le projet sont exposés. Ils valident les premières briques de l'approche retenue dans MEEQUAI

Broadband acoustic attenuation with multiresonant lossy three- dimensional sonic crystal for the train noise reduction.

International audienc

Mesure embarquée de la qualité acoustique de l'infrastructure ferroviaire

Pour les riverains des infrastructures ferroviaires, les émissions acoustiques constituent une préoccupation de premier plan. Parmi les sources incriminées, le bruit de roulement est prépondérant pour une large gamme de vitesses d'exploitation. Pour ce qui est de l'infrastructure, le niveau de bruit de roulement est principalement déterminé par deux paramètres : la rugosité des rails et le taux de décroissance des ondes vibratoires de la voie (TDR). Le projet MEEQUAI (MEsure Embarquée de la QUalité Acoustique de l'Infrastructure) vise à développer un système de mesure de la rugosité des rails et du taux de décroissance à l'aide de microphones et d'accéléromètres embarqués sur un train. Ce système a pour objectif principal d'améliorer la connaissance des données d'entrée pour la réalisation de cartographies acoustiques. Cependant, il ouvrira également de nouvelles opportunités pour le suivi dans le temps de la qualité acoustique des infrastructures ferroviaires ainsi que pour la maintenance des points singuliers tels que les joints de rail et les appareils de voie.Dans cet article, les mécanismes de génération du bruit de roulement sont présentés, notamment à travers le rôle de la rugosité et du taux de décroissance. Les principaux systèmes de mesure de ces paramètres sont passés en revue et les limites des méthodes indirectes examinées. Enfin, les résultats des premières études numériques et expérimentales réalisées dans le projet sont exposés. Ils valident les premières briques de l'approche retenue dans MEEQUAI

Calibration of transfer functions on a standstill vehicle for on-board indirect measurements of rail acoustic roughness

Forum Acusticum, LYON, FRANCE, 07-/12/2020 - 11/12/2020On-board measurement of the acoustic performance of railway tracks is nowadays necessary to qualify networks on a large scale. The issue concerns not only the supply of prediction models for strategic noise mapping, but also the optimization of track maintenance. One of the key parameters to be measured is the rail acoustic roughness. Unlike direct measurements where sensors are directly applied to the rail surface, indirect measurements of rail roughness focus on quantities that result from wheel/rail interaction, such as noise or vibrations of axle-boxes or rail, and from which the effective wheel/rail combined roughness are estimated. In particular, on-board measurements make the qualification of long track lengths possible without major constraints on traffic. A number of improvements can be made to the existing methods, especially in estimating the transfer functions between the effective roughness and the signals provided by the sensors. This study is part of the MEEQUAI French project aiming to combine modelling and measurements to optimize the estimation of the transfer functions and the location of sensors while taking into account the variability of tracks. This paper concerns the measurement performed on a static vehicle/track configuration in order to validate and calibrate the numerical simulations

Assessment of measurement-based methods for separating wheel and track contributions to railway rolling noise

The noise produced during a train pass-by originates from several different sources such as propulsion noise, noise from auxiliary equipment, aerodynamic noise and rolling noise. The rolling noise is radiated by the wheels and the track and is excited by the wheel and rail unevenness, usually referred to as roughness. The current TSI Noise certification method, which must be satisfied by all new mainline trains in Europe, relies on the use of a reference track to quantify the noise from new vehicles. The reference track is defined by an upper limit of the rail roughness and a lower limit of the track decay rate (TDR). However, since neither the rail roughness nor the track radiation can be completely neglected, the result cannot be taken as representing only the vehicle noise and the measurement does not allow separate identification of the noise radiated by wheel and track. It is even likely that further reductions in the limit values for new rolling stock cannot be achieved on current tracks. There is therefore a need for a method to separate the noise into these two components reliably and cheaply. The purpose of the current study is to assess existing and new methods for rolling noise separation. Field tests have been carried out under controlled conditions, allowing the different methods to be compared. The TWINS model is used with measured vibration data to give reference estimates of the wheel and track noise components. Six different methods are then considered that can be used to estimate the track component. It is found that most of these methods can obtain the track component of noise with acceptable accuracy. However, apart from the TWINS model, the wheel noise component could only be estimated directly using three methods and unfortunately these did not give satisfactory results in the current tests

Dataset for paper "Assessment of measurement-based methods for separating wheel and track contributions to railway rolling noise"

Dataset supports: Thompson, D. et al. (2018). Assessment of measurement-based methods for separating wheel and track contributions to railway rolling noise. Applied Acoustics.</span

Computed Tomography-Aortography Versus Color-Duplex Ultrasound for Surveillance of Endovascular Abdominal Aortic Aneurysm Repair

International audienceBackground Color-duplex ultrasonography (DUS) could be an alternative to computed tomography-aortography (CTA) in the lifelong surveillance of patients after endovascular aneurysm repair (EVAR), but there is currently no level 1 evidence. The aim of this study was to assess the diagnostic accuracy of DUS as an alternative to CTA for the follow-up of post-EVAR patients. Methods Between December 16, 2010, and June 12, 2015, we conducted a prospective, blinded, diagnostic-accuracy study, in 15 French university hospitals where EVAR was commonly performed. Participants were followed up using both DUS and CTA in a mutually blinded setup until the end of the study or until any major aneurysm-related morphological abnormality requiring reintervention or an amendment to the follow-up policy was revealed by CTA. Database was locked on October 2, 2017. Our main outcome measures were sensitivity, specificity, positive predictive value, negative predictive value, positive and negative likelihood ratios of DUS against reference standard CTA. CIs are binomial 95% CI. Results This study recruited prospectively 659 post-EVAR patients of whom 539 (82%) were eligible for further analysis. Following the baseline inclusion visit, 940 additional follow-up visits were performed in the 539 patients. Major aneurysm-related morphological abnormalities were revealed by CTA in 103 patients (17.2/100 person-years [95% CI, 13.9–20.5]). DUS accurately identified 40 patients where a major aneurysm-related morphological abnormality was present (sensitivity, 39% [95% CI, 29–48]) and 403 of 436 patients with negative CTA (specificity, 92% [95% CI, 90–95]). The negative predictive value and positive predictive value of DUS were 92% (95% CI, 90–95) and 39% (95% CI, 27–50), respectively. The positive likelihood ratio was 4.87 (95% CI, 2.9–9.6). DUS sensitivity reached 73% (95% CI, 51–96) in patients requiring an effective reintervention. Conclusions DUS had an overall low sensitivity in the follow-up of patients after EVAR, but its performance improved meaningfully when the subset of patients requiring effective reinterventions was considered. Registration URL: https://www.clinicaltrials.gov ; Unique identifier: NCT01230203