April 6, 2022

The future of e-mobility without acoustic disturbances – efficient optimisation of NVH behaviour in electric powertrains

The masking of interfering noises by the internal combustion engine is no longer present in electric vehicles. As a result, the noise of both existing and recently introduced components and assemblies has become the focus of attention.
The future of e-mobility without acoustic disturbances – efficient optimisation of NVH behaviour in electric powertrains

The OEMs now face several new challenges that require comprehensive optimisation approaches regarding NVH behaviour, where NVH (Noise - Vibration - Harshness) encompasses all perceptible and audible vibrations that significantly influence driving comfort.

Optimised systems and product characteristics achieved through balancing of all design requirements, considering all potential design conflicts 

The requirements of modern systems with respect to their functionality, acoustic behaviour, service life and industrialisability are in considerable conflict with each other. As a system supplier, we achieve the best compromise between the different requirements and possibilities, offering the most efficient solutions from a one-stop-shop. 


Due to the modular system design consisting of electric motor, power electronics and transmission, hofer powertrain delivers time- and cost-efficient customised electric drive units (EDU), constantly monitoring the different NVH aspects.   

We carry out acoustic analysis of customer and supplier systems in various sample phases on test benches or in-vehicle. The data, we obtain on the NVH behaviour, combined with our simulation capabilities allow early identification of adaptation potentials and forecasts of the NVH behaviour in series-production vehicles later in the development process. 


NVH testing services throughout the automotive development process  

The level of noise and vibration is a significant factor determining the acceptance and satisfaction of the end consumer. To recognise potentials as early as possible in an engineering process, our NVH teams operate in a highly collaborative manner across the simulation and experimental analysis disciplines. A holistic system approach plays an essential role in implementing vehicle concepts, and NVH must be considered an integral part of every vehicle design.

hofer powertrain NVH core competencies:  

  • Design and optimisation of gears sets 
  • Analysis and optimisation of dynamic structural characteristics in the transmission / Electric Drive Units (EDUs)   
  • Analysis of structure borne and airborne noise on the encapsulated powertrain test bench 
  • Selection and development of decoupling elements for complete EDUs as well as numerous auxiliary systems (e.g. thermal management)    
  • Benchmark analysis at vehicle and component level 

Excellent NVH behaviour in relevant driving situations for increased passenger comfort 

A deep understanding of scenarios and situations in e-mobility, majorly influencing the NVH behaviour in vehicles, is essential for efficient development and precise design of components in the overall drive system.     

In situations with low masking noise levels, electric vehicles are expected to operate correspondingly quietly. It applies especially in relatively calm driving situations without distractions, i.e. driving with activated cruise control, starting the car or accelerating slowly in steadily flowing traffic. But also, while approaching traffic lights, with recuperating e-motor, or in stop-and-go traffic, the NVH performance needs to be at its best. The so-called "whining" or "whistling" sounds coming from the transmission, or the power electronics stand out particularly at speeds below 100km/h. They appear in a frequency range that is still very unfamiliar to the vehicle passengers and scientifically known to be unfavourable from a psychoacoustic point of view.

With higher speeds on the motorway, the wind and the noises from the tyres increase significantly again, so that a natural masking effect occurs. 

Effective NVH analysis and appropriate adjustments in the transmission – gear sets design for reliable operation at various loads    

Stress distribution in the gear contacts using KISSsoft 

Sources of noise in EDUs typically include power electronics, the electric motor, and the transmission. However, the gearbox is considered the primary source of noise and often requires special attention.    


For several decades, the design and industrialisation of a wide range of transmission concepts have been part of hofer powertrain's core competencies. The accumulated experience and key learnings gained in past customer projects are incorporated into all future developments and provide our customers with a significant advantage in the form of shorter development cycles, enabling the most efficient realisation of tomorrow's drive concepts.   


Here, conflicting requirements are considered and weighed up against each other in the gear set design. Our experts optimise the gear contacts to ideally suit the critical load and speed points with all relevant operating scenarios in mind. hofer powertrain engineers achieve state-of-the-art balance between NVH behaviour and service life by means of simulative prediction of the transmission error accompanied by an experimental determination of the contact pattern.  



Find out more about hofer powertrain NVH expertise and services in the field of acoustic optimisation for your development projects, visit our website or contact our NVH specialists directly here.

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