COVID-19 has disrupted almost every single economy around the world and quite possibly changed our daily lives indefinitely. Although the railway industry hasn’t gone unscathed, one thing remains true: essential people and goods must still be transported from place to place.
Therefore, it comes as no surprise that offering this vulnerable group of passengers a comfortable and enjoyable ride is essential for rail companies during this most sensitive economical time. It also remains essential that trains, whether transporting passengers or goods, keep noise to a minimum so as not to disturb the surrounding ecosystem. So then, what are the crucial differentiators for railway operators? Interior and exterior noise. Imagine being handed a roadmap on eliminating both, in a single environment, in as little time and with the fewest resources possible?
Sound propagation occurs when vibrations from the noise source introduce energy into the system to the receiver – passing through the structure, substructures, and the air. This describes the transmission path. We typically define a receiver as a specific location within or external to the source. For instance, depending on the source’s frequency, something as simple as a seat could absorb the noise, while complex paths contained in structures, such as walls and open spaces, can diffract, echo, or perpetuate the noise.
A train’s predominant interior noise sources include HVAC systems & pumps, rolling noise resulting from the imperfections and roughness of the wheel & rail interface, and aerodynamic ‘flow-induced’ excitation. All of these challenges make acoustic engineering a central focus for rail designers and engineers.
Now the question becomes, how can train manufacturers ensure that their carriages are quiet enough for optimum passenger comfort?
Design teams are successfully using Virtual Prototyping to reduce and refine onboard noise. Designers use predictive solutions to foresee, analyze, and manage radiated wheel & rail noise issues, as well as propagation both inside and outside of the train, to meet challenging targets at strategic points in the train’s carriage.
Through Virtual Prototyping, engineers can utilize techniques such as Statistical Energy Analysis (SEA) to predict interior noise at critical locations inside of the cabin, accounting for the contribution from all noise sources and paths in the system. Onboard noise sources combined in a system model, including structural variants such as extruded panels or composite structures, can be evaluated in a single model to attain interior noise targets specified by rail operators.
Hybrid FE-SEA analysis is a real leap forward when it comes to acoustical modeling technologies and is likely to set the standard for industrial computational acoustics of large structures for the future. The innovative integration of FE and SEA methods within one model allows the user to solve problems that cannot be addressed by applying SEA or FE methods separately.Ulf OrreniusSenior Acoustics and Vibration Specialist, Bombardier Transportation
ESI VA One allows engineers to use these tools to assess the sound levels at a receiver location and then determine how features within an acoustic space (carpets, curtains, etc.,) absorb the sound. Engineers can use this information to optimize the acoustic space’s features to limit noise, leading to a quiet space and comfortable passengers
The same rails that carry passengers by day also carry goods, frequently by night. Now the concern is not only onboard comfort but also the comfort of the people living and working near these tracks. Because of this and the increase in traffic density, rail transport is increasingly regulated by local bylaws. These bylaws specifically limit pass-by noise of rail rolling stock near settlements (homes and businesses). Naturally, complying with these rules becomes a major issue for rail operators as their work cannot be performed if rolling stock noise levels exceed legislative guidelines.
An even more complex problem arises for freight trains. A fully loaded liquid tanker behaves differently to an empty tanker upon its return trip. Additionally, when designers are trying to predict exterior rolling stock noise, their main concern is the predictive model’s size, which is directly correlated to the rolling stock’s actual size. Designers are liable to end up with extremely large models – but that’s not all. As the train moves, its speed varies. This forces engineers to account for huge models, which alone can take several hours or even days, and now at varying speeds. Additionally, exterior noise requires that engineers use deterministic tools to calculate time intervals, resulting in large, repeated computations, both costly in computing infrastructure and time.
VA One provides a full simulation capability to predict pass-by noise early in the design process to avoid costly rework at a later stage. This is possible using the new “Rail Modeler” tool developed by ESI as part of a three-year-long project supported by the Technology Agency of the Czech Republic (TACR). It calculates complex noise sources arising from wheel & rail interaction and uses optimized Boundary Element calculations to predict the noise in intervals necessary for detailed prediction of exterior noise.
Using the Rail Modeler, designers can perform ‘what if’ exterior noise analysis to investigate the effects of both rolling stock loading and differing train speeds. This provides rolling stock designs that comply with exterior noise thresholds, which ensures rail operators can confidently achieve ROI targets.
Well, maybe it’s a few clicks away – but wouldn’t you agree that a few clicks are still far better than the alternative? Virtual Prototyping not only hands you all of the tools you need to minimize interior and exterior noise for your railway cars, but it gives you the power to do so in the least amount of time and with as few resources as possible, all while meeting local bylaws.
For more information visit: Eliminate Interior and Exterior Noise Issues Before Production with a Single Comprehensive Tool
Learn more about Designing the Quietest Railway with Exterior Acoustics Simulation