Interior Noise Simulation Research Articles

Validation of rolling-stock interior noise simulation in viaduct and tunnel environments

Acoustic comfort for modern rolling stock is a standard design requirement. The use of standard measurement conditions (ballast and free-field conditions) is the best way to identify quiet vehicles but operators (specially metro operators and some suburban) prefer to set noise targets in their own infrastructure. Metro infrastructures are mainly today done with ballastless tracks either in elevated track (viaduct) or tunnels. Therefore it is critical for rolling stock suppliers to develop methodologies to simulate interior noise performances on those scenarios to be able to propose design solutions and to control the risks. In this paper, the methodology used by Alstom to simulate interior noise in tunnels and viaduct is described. Methodology uses databases of acoustic transfer functions between sound power level of noise sources and acoustic wall pressures around vehicles. These transfer functions are modified in function of the environment (viaduct or tunnel) taking into account the type of acoustic field. Then, analytical or numerical models of the train structure plus interiors are calculated. Simulation cases and validation of the models are discussed to evaluate the pertinence of using virtual validation instead of interior noise type tests.

Equivalence study on hollow extruded aluminum alloy profile plates based on vibroacoustic behavior

For noise simulation of a high-speed train passenger compartment, an equivalence study of vehicle body hollowaluminumprofiles is imperative for reducing the finite element calculation in the simulation process and adapting to the requirements of statistical energy analysis. From the perspective of structural vibration and acoustic radiation, hollow aluminum flooring was used as an example. This study provides a noise-, vibration-, harshness-(NVH) equivalent plate acquisition method for hollow profiles and plates and studies the engineering application conditions and deviations of the equivalent structure. In accordance with the NVH-equivalent method for hollow profiles, a basic process is furnished for acquiring the properties and parameters of the equivalent plate. The consistency of vibration and noise insulation between the equivalent plate and hollow profiles plate has been validated through simulation. An electric multiple unit (EMU) interior noise simulation example showed that for an interior noise simulation model using equivalent plates, the prediction accuracy of interior noise can meet the requirements of engineering applications while significantly reducing the simulation time.

A full-spectrum analysis of high-speed train interior noise under multi-physical-field coupling excitations

High-speed-railway-train interior noise at low, medium, and high frequencies could be simulated by finite element analysis (FEA) or boundary element analysis (BEA), hybrid finite element analysis–statistical energy analysis (FEA–SEA) and statistical energy analysis (SEA), respectively. First, a new method named statistical acoustic energy flow (SAEF) is proposed, which can be applied to the full-spectrum HST interior noise simulation (including low, medium, and high frequencies) with only one model. In an SAEF model, the corresponding multi-physical-field coupling excitations are firstly fully considered and coupled to excite the interior noise. The interior noise attenuated by sound insulation panels of carriage is simulated through modeling the inflow acoustic energy from the exterior excitations into the interior acoustic cavities. Rigid multi-body dynamics, fast multi-pole BEA, and large-eddy simulation with indirect boundary element analysis are first employed to extract the multi-physical-field excitations, which include the wheel–rail interaction forces/secondary suspension forces, the wheel–rail rolling noise, and aerodynamic noise, respectively. All the peak values and their frequency bands of the simulated acoustic excitations are validated with those from the noise source identification test. Besides, the measured equipment noise inside equipment compartment is used as one of the excitation sources which contribute to the interior noise. Second, a full-trimmed FE carriage model is firstly constructed, and the simulated modal shapes and frequencies agree well with the measured ones, which has validated the global FE carriage model as well as the local FE models of the aluminum alloy–trim composite panel. Thus, the sound transmission loss model of any composite panel has indirectly been validated. Finally, the SAEF model of the carriage is constructed based on the accurate FE model and stimulated by the multi-physical-field excitations. The results show that the trend of the simulated 1/3 octave band sound pressure spectrum agrees well with that of the on-site-measured one. The deviation between the simulated and measured overall sound pressure level (SPL) is 2.6dB(A) and well controlled below the engineering tolerance limit, which has validated the SAEF model in the full-spectrum analysis of the high speed train interior noise.

Prediction of virtual interior noise

The overall impression that a vehicle creates is strongly influenced by its acoustic behaviour. In addition to the various excitation mechanisms, the transfer behaviour of the body in particular has a critical influence on the character of the interior noise. During the vehicle development process, key decisions need to be taken with regard to the vehicle body before the first prototypes exist as hardware. To support this process, a virtual noise prediction system has been developed at FEV that combines the established experimental method of interior noise simulation with an FE calculation for the vehicle body.

Vehicle Interior Noise Simulation as a Production Vehicle Development Tool

A key portion of the Noise, Vibration and Harshness (NVH) development process is the use of an approach called Vehicle Interior Noise Simulation (VINS). The tool, which was developed by FEV, is based on an analytical method that divides the total interior noise into audible noise shares from different paths and allows each path to be further broken down into source and transfer function components. VINS establishes a highly effective platform for the dedicated assessment of simulation and physical test results.

Vehicle exterior noise simulation

Analogous to interior noise simulation, which has been in use as a standard procedure for some time, FEV Motorentechnik developed a method for vehicle exterior noise simulation to support the automotive industry’s development activities in this field. With this method, the total noise can be assigned to the individual noise paths which are then analyzed regarding excitation, transfer behavior and frequency content. Thus, development activities can be focused on the dominant noise sources and the weak points of the vehicle and engine.

実験と数値解析を用いた高速鉄道車両の車内静音化(振動・騒音実験・解析技術,特別オーガナイズドセッション「音色・音質設計技術〜開発者と利用者・第三者を繋ぐ」,振動・騒音改善技術)

To reduce the interior noise in high-speed trains, we have built several interior noise simulation models based on statistical energy analysis and boundary element analysis. By comparing the noise calculated using these models with the measured interior noise in train cars, running through various sections at various speeds, we have confirmed the models is accurate within 1.5 dB for the overall noise level We therefore used them to evaluate contribution factors of the interior panel radiation to the interior noise and to evaluate the effectiveness of several countermeasures. This procedure could be used to design optimal structures for large and quiet passenger cabins.

Sound design from the aspect of musical harmony

FEV’s sound design strategy is based on proprietary vehicle interior and exterior noise simulation methods with an emphasis on achieving desired sounds with hardware solutions suitable for series production. This article discusses a new aspect of sound design: the comparison of musical harmonic theory with engine noises. From this, important new insights regarding noise characteristics that are objectively melodious in musical terms can be gained and transferred to the vehicle. The results presented here were obtained within an internal research project at FEV Motorentechnik.

Vehicle interior noise simulation for evaluating the prototype powertrains in the vehicle — Part 2

Vehicle interior noise simulation for evaluating the prototype powertrains in the vehicle — Part 2

Vehicle interior noise simulation for evaluating prototype powertrains in the vehicle — Part 1

In the recent past, interior noise quality has developed into a decisive aspect of the evaluation of overall vehicle quality. At most operating points, the majority of the interior noise is generated by the powertrain. This paper by FEV Motorentechnik GmbH, Aachen, describes how interior noise simulation can be implemented to improve vehicle acoustics.

Vehicle interior noise simulation for coupled acoustic-structural systems

Vehicle interior noise simulation for coupled acoustic-structural systems