Tests can be run using components or different assembly levels.

Everyone has different reactions to the minor and major frustrations that pop up on an average day. Vehicle noises, especially interior vibration noises, are one of those things that can drive a person mad. Some people let a buzzing noise go on for days or months because they either tune it out or don’t hear the noise. Others faced with a vibrating sound in their car start a CSI-level investigation to find the source of the noise. This is particularly true with a new car, a low or high frequency buzz in a new car is a major dissatisfier that comes up in ownership surveys.

A digital prototype helps automakers to understand noise concerns. (Image courtesy of Siemens.)

Siemens has technology to help automakers find the sources of noise and vibration in a vehicle model, such as the system prediction functions for Simcenter built to help reduce NVH (noise, vibration, harshness) concerns. The application will focus on simulating assemblies and pushing the identification of noise risks earlier in the development time line, during the design phase.

Siemens is greatly involved in working with vehicle NVH and acoustic issues. This focus looks at the negative effects that noise issues can have on a vehicle and the customer’s perception of the brand. As with most simulations, the goals revolve around shortening a project’s development time and finding ways to expose problems in the digital world before physical prototypes or production assemblies exhibit the issue.

One of the case studies that Siemens presents involves Hitachi Automotive Systems and using transfer path analysis (TPA) to reduce the number of physical prototypes needed for a test. Using Simcenter Testlab and moving some of the high-level testing to Siemens led Hitachi engineer Hayuru Inoue to estimate a “50 percent time reduction in prototyping, component testing and vehicle testing” for the project.

Another case study based on Volvo construction equipment, focused on better comfort and noise characteristics for heavy equipment. On small wheel loaders, when the drive shaft was operating at speeds higher than 2,400 rpm, a whining noise could be heard in the driver’s cab. This noise only occurred under certain conditions and in specific positions of the drive shaft, so it was difficult to replicate and troubleshoot. Using several different methods inside Simcenter Testlab, the companies were able to find probable causes for the whining noise and propose design solutions.

Simona Ottaiano, from Siemens, asks a big question in her article “Master the vehicle NVH performance with a virtual prototype”: Does understanding the performance of individual components mean that you understand the vehicle assembly? The answer is a pretty definite “no,” because assembly adds dozens of levels of complexity to the NVH environment.

Virtual vehicles are built using different component configurations. (Image courtesy of Siemens.)

In my time as an automotive engineer, the original equipment manufacturers (OEMs) had several methods to determine how assembly and subassembly would be handled. Most of those methods were based on money, time and quality. After building steering column assemblies, we would ship them to a sequencer that would place the steering columns into an instrument panel assembly. That second subassembly would be loaded into a truck and sent to the vehicle assembly plant. However, several of the parts on the steering columns were subassemblies, some with two additional levels of subassembly complexity.

Using the NVH functions of Simcenter Testlab’s Virtual Prototype Assembly (VPA), Ottaiano says that engineers can take component models and assemble them in different configurations to find areas where noise or vibration might occur. Additionally, using the virtual prototypes will enable engineers to create separate models for each of the manufacturer’s vehicle options. The first step is finding “accurate and validated” component models to use in building the assemblies.

Automotive components have specialized part names, supplier- and customer-specific part numbers, and the common names used by their designers. Engineers can use Testlab VPA Definition to give specific identities to each of the parts. Templates can be built for each part or part family to give consistent interface parameters in the system.

Noise analysis is run for different component configurations. (Image courtesy of Siemens.)

Siemens works to define the different noises that might pop in during vehicle operation. Booming noises, road noises and pass-by noises are covered during analysis, and results can be shown for a vehicle’s interior or exterior. Different configurations will make differing noise profiles, and a vehicle with different steering packages, seating options or technology will create its own unique set of possible issues. Using the built-in Data Management applications helps engineers to keep each configuration separate and to know what each individual option might do to a full assembly’s performance.

Collaboration also becomes more important as organizations become larger. A project manager might need to share information with their customers, suppliers, in-house manufacturing team, shipping and packaging engineers, among others. The Siemens PLM and Teamcenter software is another tool that can help engineers to ensure that their NVH studies reach the people who need them.

As more and more hybrid and fully electric vehicles are developed, the noise profiles of vehicles are changing. The internal combustion might have been hiding some sounds that are now coming to light as electric motors run much quieter. Some manufacturers know this and are trying to redefine how they want their vehicles to sound. Vehicles moving at speeds up to 18.6 miles per hour are also required to make some sound, as a precaution against their quiet operation surprising pedestrians and causing accidents. The “quiet car” rule says that these vehicles must emit sounds between 43 and 64 decibels, although the National Highway Traffic Safety Administration has given automakers a few pandemic extensions on implementing this regulation. The Acoustic Vehicle Alerting System (AVAS) is a relatively new requirement for vehicles that we can expect to become a permanent part of the automotive landscape.

Manufacturers are trying different methods to address the problem of wanting some noise to come from their electric vehicles right in the zone where the noise doesn’t become a customer dissatisfier. BMW is working with composer Hans Zimmer to find the right sound for its electric vehicles to emit for safe operation. Hyundai has shifted to a  Road-Noise Active Control (RANC) system that chooses to proactively take the noise out of its operations instead of adding passive components like noise-absorbing foam or dampening pieces. This becomes more complicated when specific noises from an electric vehicle are factored in. The aftermarket industry, of course, never misses an opportunity to sell hyper-specific parts to consumers. Several options are available for speaker sets that connect to both vehicles’ interior or exterior to change the noise profile.

Siemens believes that focusing on the person in the vehicle is one of the keys to developing the best electric vehicle noise profile. Steven Dom from Siemens says that at some point there might be a little psychology and human mind science built into our engineering designs. Using the Siemens SimRod electric vehicle, Dom and his team are “having fun” figuring out exactly what noises they want an electric vehicle to emit and how to create a digital twin that will reproduce those noises. Simcenter’s new NVH capabilities will come in handy as it continues to develop new tools for understanding vehicle noise for electric and internal combustion models.

The approach that Siemens is taking here is interesting because there’s no new product. The “system NVH prediction solution” seems like something that should get its own shiny name and a full tab on the Simcenter website. That might be coming, but right now the solution exists as an inventive application that uses the pieces of Testlab in a new and novel way.

The focus for most of this activity is on simulation studies that happen very early in the design cycle and are meant to shave time and development costs from a project. There’s another aspect of vehicle production that is seemingly missed here—the analysis of changes made to vehicles already in production. There was a decade or so where cost savings were found by making small incremental changes after production started. These changes were often made on a very micro level without a complete understanding of the overall effects they’d have on the next level of subassembly or final vehicle assembly. Using a tool like Siemens NVH prediction could help manufacturers to understand how a small change can modify the NVH levels across the vehicle.

In the next few years, it will be interesting to watch these software tools evolve and find ways to create better noise profiles. Whether the goal is reducing road noise or finding a way to bump up the sounds of electric vehicle, the NVH portion of Simcenter Testlab is in a good position to drive the discussion.