Home appliance manufacturer optimizes acoustics and vibration product testing with Simcenter Testlab

Washing machines, dishwashers and refrigerators are expected to perform their inherent functions quietly and without drawing attention. With clean clothes, spotless dishes and cold food being a customer’s main concern when selecting an appliance, the average consumer has no idea about the competition between leading home appliance product manufacturers to reach optimum noise and vibration levels. Electronics and semiconductor BSH Home appliance manufacturer optimizes acoustics and vibration product testing with Simcenter Testlab “The importance of this parameter increases yearly,” says Otto Petraška, head of vibrations and acoustics department, BSH. “It is even a criterion that can stop the serial production of some of the products.”

The BSH Vibrations and Acoustics Department in Košice, Slovakia, is responsible for the acoustic and vibration performance of the electric motors produced by BSH Drives and Pumps in Michalovce, Slovakia.

Formed in 2004, Vibrations and Acoustics department provides services in noise and vibration optimization of household appliances manufactured by BSH under the main brands of Bosch and Siemens. Featuring 16 in-house experts, they serve eight other divisions of Robert Bosch and are involved in the optimization of noise and vibration parameters for all products, from garden tools to electric car engines.

Sound quality for home appliances

The Vibrations and Acoustics department uses a variety of psychoacoustic tools to ensure that premium washing machines and dishwashers meet customer expectations. BSH’s Košice laboratory for sound quality uses state-of-the-art tools and techniques to research sound recordings. They measure the sound quality of home appliances by using binaural heads in a high- quality anechoic chamber to ensure accurate sound representation and analysis.

“We’re conducting tests with groups of people for whom we’re playing sound samples,” says Otto Petraška. “Based on their assessment, we set the acoustic target to meet customer expectations. At the same time, we want to be sure the sound is powerful and has a certain strength without being overbearing.”

Rastislav Andrejco, senior center specialist for acoustics and vibrations at BSH, adds, “Customers expect a washing machine to sound like sprinkling water, an extractor hood to sound like wind, and a coffee maker to sound like drops of coffee.”

Sound engineering in the early stage of product development

Every component of a product can influence its overall sound. As products are being developed, changes and adaptations are necessary for successful sound engineering. “The sooner we are involved in the development process, the better we can eliminate early product bugs that may produce noise problems at the end of the process,” says Otto Petraška. “Of course, it is also more cost-effective than dealing with something at the last minute.”

With the collaboration of BSH Drives Development department in Michalovce, this approach is taken for the 14 million electric motors annually produced for all appliances manufactured by BSH under the main brands of Bosch and Siemens. The team in Michalovce is responsible for the design of the electric motors, while the research group in Košice is responsible for the acoustic and vibrational parameters.

The fully equipped semi-anechoic chamber enables additional sound design engineering.

Two teams, one digital twin

Košice’s acoustics researchers are involved in the early stages of the engine development process. The development team in Michalovce designs an engine comprised of an electromagnetic rotor and stator design (1D model), creating a digital twin. This virtual model provides the ability to simulate its activity and load and verify all outputs, from physical to operational.

At the same time, the simulation model enables the development team to fine-tune the sound and vibration design parameters before manufacturing a prototype. Using Simcenter™ 3D, the engineer creates simulation models. This allows them to perform vibrational and acoustic analyses throughout the development cycle. They evaluate the engine’s vibro-acoustic characteristics and identify the source of an individual component’s noise and vibration. If necessary, they recommend design improvements for the engine’s noise and vibration performance without negatively affecting product functionality and production cost. The effect of the design optimization is verified using the Simcenter Testlab™ solution from Siemens Digital Industries Software.

“With Simcenter Testlab, we can intervene at any stage of the simulation chain and find out how the change will be reflected in the basic design,” says Otto Petraška. “For example, when it comes to the engine’s structure, when some of its parts create sound we can have a technical remedy. But if the problem arises from the electromagnetic design itself, we return to Drives Development department and optimize the basic design. We experience a number of such loops in the development of a new engine.”

The synergy between physical testing and simulation

The BSH Vibrations and Acoustics Department began using digital tools in 2008, deploying simulation and test software from Siemens Digital Industries Software’s Simcenter portfolio for full data compatibility.

“Simcenter allows us to strongly correlate simulations with experimental tests that are very important, because without them, the simulations would simply be nice colored pictures,” says Otto Petraška.

BSH uses Simcenter Testlab in combination with Simcenter 3D simulations. “We perceived benefits of using these interconnected products and we use the synergies offered by them,” says Ján Ondrejčák, senior development engineer, BSH. “We notice the effectiveness and user-friendli- ness of all the Simcenter noise and vibration solutions.”

Through experimental testing, the team verifies whether the simulation parameters are correctly set and if the results are reliable. They also use tests to debug all possible variants and adjustments. “If the simulation shows an optimal result, the product is manufactured into a real prototype,” says Otto Petraška. “We can only build a physical prototype when we are sure that we have achieved the best possible result.”

With digitalization, development times are continually shrinking. What used to take weeks can now be completed in days; and some time-consuming simulations have been shortened from days to mere hours. As simulation models become more advanced, simulation engineers will be able to anticipate a product’s long-term behavior.

“We want to assure the customer that our product will retain the same noise and vibrational performance after years of operation as it did on the day they purchased it,” says Otto Petraška. “That builds trust in our brand and we hope to convince them to buy our next generation of appliances.”